Student
From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Student (disambiguation).
Students attending a lecture on linear algebra at the Helsinki University of Technology
The word student is etymologically derived through Middle English from the Latin second-type conjugation verb "studēre", meaning "to direct one's zeal at"; hence a student could be described as 'one who directs zeal at a subject'. In its widest use, "student" is used for anyone who is learning.
Contents[hide]
1 Scope
2 International variations
2.1 Australia
2.2 Canada
2.3 Continental Europe
2.4 United Kingdom and Ireland
2.5 United States
2.5.1 Before first year
2.5.2 First year
2.5.3 Second year
2.5.4 Post-second year
3 Mature students
4 Student pranks
5 Other terms
6 Idiomatic use
7 See also
8 References
//
[edit] Scope
In many countries, the word "student" or a cognate equivalent (e.g., French "étudiant") is reserved for higher education or university students. However derived adjectives in such languages (e.g., "estudiantin" in French) may also, or even especially (e.g., Dutch "studentikoos"), be associated with the non-academic, fun-loving side of stereotyped "student life" (in part organised, such as hazing, "Greek life" in North American Fraternities and sororities), although not all students indulge in this lifestyle.
[edit] International variations
Students in rural Sudan, 2002
Over one thousand students in uniform during an assembly at a secondary school in Singapore.
[edit] Australia
In Australia, after Kindergarten, "year one", "year two", etc. through to "year twelve" are in most common usage. Children in primary and secondary school are all referred to as students. The term student is used for all learners including primary school, secondary school and university/TAFE.
[edit] Canada
In Canada, special terms are occasionally used. In English provinces, the high school (known as Academy or secondary school) years can be referred to simply as first, second, third, fourth and fifth year. Some areas call it by grade such as Grade 10, Grade 11 and Grade 12. Provincial variations can include Grade 9 in High School, though most in most provinces, Grades 10 through 12 are considered High School, with Grades 7 through 9 called "Junior High." In university, students are classified as first-, second-, third-, or fourth-year students. In some occasions, they can be called Senior Ones, Twos, Threes, and Fours. First years are commonly known as "frosh", and the first week of university for first year students is commonly known as Frosh week.
[edit] Continental Europe
In Belgian universities, first-year students are called schacht in Flemish, or bleu in French. In Macedonian they are called бруцош.
[edit] United Kingdom and Ireland
The term student is usually reserved for people studying at University level in the UK. Children studying at school are called pupils.
In England and Wales, teenagers in the last two years of school are called "sixth formers". If pupils follow the average pattern of school attendance, pupils will be in the "lower sixth" between the ages of 16 and 17, and the "upper sixth" between 17 and 18. They "go up" to University after the upper sixth.
In Scotland pupils sit Highers at the end of fifth year (when aged 16-17) after which it is possible for them to gain entry to university. However, many do not achieve the required grades and remain at school for sixth year. Even among those that do achieve the necessary grades it is common to remain at school and undertake further study (i.e. other subjects or Advanced Highers) and then start university at the same time as their friends and peers.
At universities in the United Kingdom and Ireland the term "fresher" is used to describe new students who are just beginning their first year. It would be unusual to call someone a fresher after their first few weeks at University. There is little derogatory connotation to this name in the UK, except for an occasional reference to "freshers" in a tone that implies naivety. More commonly, it will be used in a kindly fashion. For instance, a University official might ask a student if they are a fresher without any hint of a put down.
The term "first year" is the more commonly used, and connotation free, term for students in their first year. The week at the start of a new year is called "Freshers' Week", with a programme of special events to welcome new students; some universities, however, are attempting to drop the connotative associations of "freshers' week" by renaming it "welcome week".[citation needed] An undergraduate in the last year of study before graduation is generally known as a "finalist", or simply a third year (in England, Wales, and Northern Ireland ) or a fourth year (in Scotland and the Republic of Ireland).
A student in the United Kingdom
The ancient Scottish University of St Andrews uses the terms "bejant" for a first year (from the French "bec-jaune" – "yellow beak", "fledgling"). Second years are called "semi-bejants", third years are known as "tertians", and fourth years, or others in their final year of study, are called "magistrands".
For pupils, first of all is primary school and it starts off with Reception (similar to Kindergarten) and then move on to "year one, Year two" and so on until "year six". Children join secondary school in year 7 (when they are 11-12 year olds) up to year 11 and then after is sixth form, whereas a student entering a fee-paying school (usually a year later) would join the "third form"- equivalent to year 9- many schools have an alternate name for first years, some with a derogatory basis, but in others acting merely as a description- for example "shells"(non-derogatory) or "grubs"(derogatory.)
[edit] United States
[edit] Before first year
Some schools use the term "prefrosh" or "pre-frosh" to describe their newly admitted students. Schools often offer a campus preview weekend for prefroshes to know the schools better. A student is considered a prefrosh until he or she registers for the first class.
[edit] First year
A freshman (slang alternatives that are usually derogatory in nature include "fish", "fresher", "frosh", "newbie", "freshie", "snotter", "fresh-meat", etc.) is a first-year student in college, university or high school. The less-common[citation needed] gender-neutral synonym "first-year student" exists; the variation "freshperson" is rare.[citation needed]
In many traditions there is a remainder of the ancient (boarding, pre-commuting) tradition of fagging. He may also be subjected to a period of hazing or ragging as a pledge(r) or rookie, especially if joining a fraternity/sorority or certain other clubs, mainly athletic teams. For example, many high schools have initiation methods for freshmen, including, but not limited to, Freshman Duct-taped Throw, Freshman races, Freshman Orientation, Freshman Freshening (referring to poor hygiene among freshmen), and the Freshman Spread.
Even after that, specific rules may apply depending on the school's traditions (e.g., wearing a distinctive beanie), non-observance of which may result in punishment in which the paddle may come into play.
[edit] Second year
In the U.S., a sophomore is a second-year student. Folk etymology has it that the word means "wise fool"; consequently "sophomoric" means "pretentious, bombastic, inflated in style or manner; immature, crude, superficial" (according to the Oxford English Dictionary). It appears to be most likely formed from Greek "sophos", meaning "wise", and "moros" meaning "foolish", although it may also have separately originated from the word "sophumer", an obsolete variant of "sophism"[1]. Outside of the U.S. the term "sophomore" is rarely used, with second-year students simply called "second years".
Academic procession during the University of Canterbury graduation ceremony.
[edit] Post-second year
In the U.S. a "junior" is a student in the penultimate (usually third) year and a "senior" a student in the last (usually fourth) year of college, university, or high school. A college student who takes more than the normal number of years to graduate is sometimes referred to as a "super senior".[2] The term "underclassman" is used to refer collectively to freshmen and sophomores, and "upperclassman" to refer collectively to juniors and seniors, sometimes even sophomores. The term "middler" is used to describe a third-year student of a school (generally college) which offers five years of study. In this situation, the fourth and fifth years would be referred to as "junior" and "senior" years, respectively.
[edit] Mature students
Main article: Mature student
A mature, or adult student in tertiary education (at a university or a college) is normally classified as an (undergraduate) student who is at least 21 - 23 years old at the start of their course and usually having been out of the education system for at least two years. Mature students can also include students who have been out of the education system for decades, or students with no secondary education. Mature students also make up graduate and postgraduate populations by demographic of age.
[edit] Student pranks
Main article: Student prank
University students have a long association with pranks and japes.[3][4][5][6][7] These can often involve petty crime, such as the theft of traffic cones and other public property,[8] or hoaxes. It is also not uncommon for students from one school to steal or deface the mascot of a rival school.[9] In fact, pranks play such a significant part in student culture that numerous books have been published that focus on the issue.[10][11]Pranks may reflect current events[12], be a form of protest or revenge, or have no other purpose than for the enjoyment of the prank itself. A recent report has been released focusing on the misbehaviour of university students. The report, Studentification: A Guide to Opportunities, Challenges and Practice, by Universities UK, focuses on six British universities as case studies.
[edit] Other terms
A student who is repeating a grade level of schooling due to poor grades is sometimes referred to as having been "held back".
The term pupil (originally a Latin term for a minor as the ward of an adult guardian etc.) is used in British primary and secondary schools instead of "student", but once attending higher education such as sixth-form college etc, the term "student" is standard.
The United States military academies use only numerical terms, except there are colloquial expressions used in everyday speech. In order from first year to fourth year, students in these institutions are officially referred to as "fourth-class", "third-class", "second-class", and "first-class" cadets or midshipmen. Unofficially, other terms are used, for example at the United States Military Academy, freshman are called "plebes," sophomores are called "yearlings" or "yuks," juniors are called "cows," and seniors are called "firsties." Some universities also use numerical terms to identify classes; students enter as "first-years" and graduate as "fourth-years" (or, in some cases, "fifth-years", "sixth-years", etc).
Freshers' Flu refers to the generic illness that many new students get during the first few weeks of starting the first year. This is often attributed to viral/bacterial diseases being carried by students from other regions of the country/world, to which some have no immunity.[citation needed]
In the United States a "gunner" is an overly competitive student, typically in law school or medical school. Calling someone a gunner is usually highly offensive[citation needed]. A gunner is also overly ambitious and often excitedly volunteers oral answers in class that are, by turns, incorrect, off-topic, or specifically designed to demonstrate the questionable "intellectual" prowess of the person supplying them. These questions are often prefaced with phrases like "A cursory literature search revealed ... " A gunner will compromise his or her peer relationships in order to obtain recognition and praise from his or her instructors and superiors, often by directly harming or attempting to harm the academic well-being of said peers.[13]
[edit] Idiomatic use
"Freshman" and "sophomore" are sometimes used figuratively, almost exclusively in the United States, to refer to a first or second effort ("the singer's sophomore album"), or to a politician's first or second term in office ("freshman senator") or an athlete's first or second year on a professional sports team. "Junior" and "senior" are not used in this figurative way to refer to third and fourth years or efforts, because of those words' broader meanings of "younger" and "older". (A junior senator is therefore not one who is in his or her third term of office, but merely one who has not been in the Senate as long as the other senator from his or her state.)
Monday, October 20, 2008
Sunday, October 19, 2008
ENTRY 18
Student
From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Student (disambiguation).
Students attending a lecture on linear algebra at the Helsinki University of Technology
The word student is etymologically derived through Middle English from the Latin second-type conjugation verb "studēre", meaning "to direct one's zeal at"; hence a student could be described as 'one who directs zeal at a subject'. In its widest use, "student" is used for anyone who is learning.
Contents[hide]
1 Scope
2 International variations
2.1 Australia
2.2 Canada
2.3 Continental Europe
2.4 United Kingdom and Ireland
2.5 United States
2.5.1 Before first year
2.5.2 First year
2.5.3 Second year
2.5.4 Post-second year
3 Mature students
4 Student pranks
5 Other terms
6 Idiomatic use
7 See also
8 References
//
[edit] Scope
In many countries, the word "student" or a cognate equivalent (e.g., French "étudiant") is reserved for higher education or university students. However derived adjectives in such languages (e.g., "estudiantin" in French) may also, or even especially (e.g., Dutch "studentikoos"), be associated with the non-academic, fun-loving side of stereotyped "student life" (in part organised, such as hazing, "Greek life" in North American Fraternities and sororities), although not all students indulge in this lifestyle.
[edit] International variations
Students in rural Sudan, 2002
Over one thousand students in uniform during an assembly at a secondary school in Singapore.
[edit] Australia
In Australia, after Kindergarten, "year one", "year two", etc. through to "year twelve" are in most common usage. Children in primary and secondary school are all referred to as students. The term student is used for all learners including primary school, secondary school and university/TAFE.
[edit] Canada
In Canada, special terms are occasionally used. In English provinces, the high school (known as Academy or secondary school) years can be referred to simply as first, second, third, fourth and fifth year. Some areas call it by grade such as Grade 10, Grade 11 and Grade 12. Provincial variations can include Grade 9 in High School, though most in most provinces, Grades 10 through 12 are considered High School, with Grades 7 through 9 called "Junior High." In university, students are classified as first-, second-, third-, or fourth-year students. In some occasions, they can be called Senior Ones, Twos, Threes, and Fours. First years are commonly known as "frosh", and the first week of university for first year students is commonly known as Frosh week.
[edit] Continental Europe
In Belgian universities, first-year students are called schacht in Flemish, or bleu in French. In Macedonian they are called бруцош.
[edit] United Kingdom and Ireland
The term student is usually reserved for people studying at University level in the UK. Children studying at school are called pupils.
In England and Wales, teenagers in the last two years of school are called "sixth formers". If pupils follow the average pattern of school attendance, pupils will be in the "lower sixth" between the ages of 16 and 17, and the "upper sixth" between 17 and 18. They "go up" to University after the upper sixth.
In Scotland pupils sit Highers at the end of fifth year (when aged 16-17) after which it is possible for them to gain entry to university. However, many do not achieve the required grades and remain at school for sixth year. Even among those that do achieve the necessary grades it is common to remain at school and undertake further study (i.e. other subjects or Advanced Highers) and then start university at the same time as their friends and peers.
At universities in the United Kingdom and Ireland the term "fresher" is used to describe new students who are just beginning their first year. It would be unusual to call someone a fresher after their first few weeks at University. There is little derogatory connotation to this name in the UK, except for an occasional reference to "freshers" in a tone that implies naivety. More commonly, it will be used in a kindly fashion. For instance, a University official might ask a student if they are a fresher without any hint of a put down.
The term "first year" is the more commonly used, and connotation free, term for students in their first year. The week at the start of a new year is called "Freshers' Week", with a programme of special events to welcome new students; some universities, however, are attempting to drop the connotative associations of "freshers' week" by renaming it "welcome week".[citation needed] An undergraduate in the last year of study before graduation is generally known as a "finalist", or simply a third year (in England, Wales, and Northern Ireland ) or a fourth year (in Scotland and the Republic of Ireland).
A student in the United Kingdom
The ancient Scottish University of St Andrews uses the terms "bejant" for a first year (from the French "bec-jaune" – "yellow beak", "fledgling"). Second years are called "semi-bejants", third years are known as "tertians", and fourth years, or others in their final year of study, are called "magistrands".
For pupils, first of all is primary school and it starts off with Reception (similar to Kindergarten) and then move on to "year one, Year two" and so on until "year six". Children join secondary school in year 7 (when they are 11-12 year olds) up to year 11 and then after is sixth form, whereas a student entering a fee-paying school (usually a year later) would join the "third form"- equivalent to year 9- many schools have an alternate name for first years, some with a derogatory basis, but in others acting merely as a description- for example "shells"(non-derogatory) or "grubs"(derogatory.)
[edit] United States
[edit] Before first year
Some schools use the term "prefrosh" or "pre-frosh" to describe their newly admitted students. Schools often offer a campus preview weekend for prefroshes to know the schools better. A student is considered a prefrosh until he or she registers for the first class.
[edit] First year
A freshman (slang alternatives that are usually derogatory in nature include "fish", "fresher", "frosh", "newbie", "freshie", "snotter", "fresh-meat", etc.) is a first-year student in college, university or high school. The less-common[citation needed] gender-neutral synonym "first-year student" exists; the variation "freshperson" is rare.[citation needed]
In many traditions there is a remainder of the ancient (boarding, pre-commuting) tradition of fagging. He may also be subjected to a period of hazing or ragging as a pledge(r) or rookie, especially if joining a fraternity/sorority or certain other clubs, mainly athletic teams. For example, many high schools have initiation methods for freshmen, including, but not limited to, Freshman Duct-taped Throw, Freshman races, Freshman Orientation, Freshman Freshening (referring to poor hygiene among freshmen), and the Freshman Spread.
Even after that, specific rules may apply depending on the school's traditions (e.g., wearing a distinctive beanie), non-observance of which may result in punishment in which the paddle may come into play.
[edit] Second year
In the U.S., a sophomore is a second-year student. Folk etymology has it that the word means "wise fool"; consequently "sophomoric" means "pretentious, bombastic, inflated in style or manner; immature, crude, superficial" (according to the Oxford English Dictionary). It appears to be most likely formed from Greek "sophos", meaning "wise", and "moros" meaning "foolish", although it may also have separately originated from the word "sophumer", an obsolete variant of "sophism"[1]. Outside of the U.S. the term "sophomore" is rarely used, with second-year students simply called "second years".
Academic procession during the University of Canterbury graduation ceremony.
[edit] Post-second year
In the U.S. a "junior" is a student in the penultimate (usually third) year and a "senior" a student in the last (usually fourth) year of college, university, or high school. A college student who takes more than the normal number of years to graduate is sometimes referred to as a "super senior".[2] The term "underclassman" is used to refer collectively to freshmen and sophomores, and "upperclassman" to refer collectively to juniors and seniors, sometimes even sophomores. The term "middler" is used to describe a third-year student of a school (generally college) which offers five years of study. In this situation, the fourth and fifth years would be referred to as "junior" and "senior" years, respectively.
[edit] Mature students
Main article: Mature student
A mature, or adult student in tertiary education (at a university or a college) is normally classified as an (undergraduate) student who is at least 21 - 23 years old at the start of their course and usually having been out of the education system for at least two years. Mature students can also include students who have been out of the education system for decades, or students with no secondary education. Mature students also make up graduate and postgraduate populations by demographic of age.
[edit] Student pranks
Main article: Student prank
University students have a long association with pranks and japes.[3][4][5][6][7] These can often involve petty crime, such as the theft of traffic cones and other public property,[8] or hoaxes. It is also not uncommon for students from one school to steal or deface the mascot of a rival school.[9] In fact, pranks play such a significant part in student culture that numerous books have been published that focus on the issue.[10][11]Pranks may reflect current events[12], be a form of protest or revenge, or have no other purpose than for the enjoyment of the prank itself. A recent report has been released focusing on the misbehaviour of university students. The report, Studentification: A Guide to Opportunities, Challenges and Practice, by Universities UK, focuses on six British universities as case studies.
[edit] Other terms
A student who is repeating a grade level of schooling due to poor grades is sometimes referred to as having been "held back".
The term pupil (originally a Latin term for a minor as the ward of an adult guardian etc.) is used in British primary and secondary schools instead of "student", but once attending higher education such as sixth-form college etc, the term "student" is standard.
The United States military academies use only numerical terms, except there are colloquial expressions used in everyday speech. In order from first year to fourth year, students in these institutions are officially referred to as "fourth-class", "third-class", "second-class", and "first-class" cadets or midshipmen. Unofficially, other terms are used, for example at the United States Military Academy, freshman are called "plebes," sophomores are called "yearlings" or "yuks," juniors are called "cows," and seniors are called "firsties." Some universities also use numerical terms to identify classes; students enter as "first-years" and graduate as "fourth-years" (or, in some cases, "fifth-years", "sixth-years", etc).
Freshers' Flu refers to the generic illness that many new students get during the first few weeks of starting the first year. This is often attributed to viral/bacterial diseases being carried by students from other regions of the country/world, to which some have no immunity.[citation needed]
In the United States a "gunner" is an overly competitive student, typically in law school or medical school. Calling someone a gunner is usually highly offensive[citation needed]. A gunner is also overly ambitious and often excitedly volunteers oral answers in class that are, by turns, incorrect, off-topic, or specifically designed to demonstrate the questionable "intellectual" prowess of the person supplying them. These questions are often prefaced with phrases like "A cursory literature search revealed ... " A gunner will compromise his or her peer relationships in order to obtain recognition and praise from his or her instructors and superiors, often by directly harming or attempting to harm the academic well-being of said peers.[13]
[edit] Idiomatic use
"Freshman" and "sophomore" are sometimes used figuratively, almost exclusively in the United States, to refer to a first or second effort ("the singer's sophomore album"), or to a politician's first or second term in office ("freshman senator") or an athlete's first or second year on a professional sports team. "Junior" and "senior" are not used in this figurative way to refer to third and fourth years or efforts, because of those words' broader meanings of "younger" and "older". (A junior senator is therefore not one who is in his or her third term of office, but merely one who has not been in the Senate as long as the other senator from his or her state.)
From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Student (disambiguation).
Students attending a lecture on linear algebra at the Helsinki University of Technology
The word student is etymologically derived through Middle English from the Latin second-type conjugation verb "studēre", meaning "to direct one's zeal at"; hence a student could be described as 'one who directs zeal at a subject'. In its widest use, "student" is used for anyone who is learning.
Contents[hide]
1 Scope
2 International variations
2.1 Australia
2.2 Canada
2.3 Continental Europe
2.4 United Kingdom and Ireland
2.5 United States
2.5.1 Before first year
2.5.2 First year
2.5.3 Second year
2.5.4 Post-second year
3 Mature students
4 Student pranks
5 Other terms
6 Idiomatic use
7 See also
8 References
//
[edit] Scope
In many countries, the word "student" or a cognate equivalent (e.g., French "étudiant") is reserved for higher education or university students. However derived adjectives in such languages (e.g., "estudiantin" in French) may also, or even especially (e.g., Dutch "studentikoos"), be associated with the non-academic, fun-loving side of stereotyped "student life" (in part organised, such as hazing, "Greek life" in North American Fraternities and sororities), although not all students indulge in this lifestyle.
[edit] International variations
Students in rural Sudan, 2002
Over one thousand students in uniform during an assembly at a secondary school in Singapore.
[edit] Australia
In Australia, after Kindergarten, "year one", "year two", etc. through to "year twelve" are in most common usage. Children in primary and secondary school are all referred to as students. The term student is used for all learners including primary school, secondary school and university/TAFE.
[edit] Canada
In Canada, special terms are occasionally used. In English provinces, the high school (known as Academy or secondary school) years can be referred to simply as first, second, third, fourth and fifth year. Some areas call it by grade such as Grade 10, Grade 11 and Grade 12. Provincial variations can include Grade 9 in High School, though most in most provinces, Grades 10 through 12 are considered High School, with Grades 7 through 9 called "Junior High." In university, students are classified as first-, second-, third-, or fourth-year students. In some occasions, they can be called Senior Ones, Twos, Threes, and Fours. First years are commonly known as "frosh", and the first week of university for first year students is commonly known as Frosh week.
[edit] Continental Europe
In Belgian universities, first-year students are called schacht in Flemish, or bleu in French. In Macedonian they are called бруцош.
[edit] United Kingdom and Ireland
The term student is usually reserved for people studying at University level in the UK. Children studying at school are called pupils.
In England and Wales, teenagers in the last two years of school are called "sixth formers". If pupils follow the average pattern of school attendance, pupils will be in the "lower sixth" between the ages of 16 and 17, and the "upper sixth" between 17 and 18. They "go up" to University after the upper sixth.
In Scotland pupils sit Highers at the end of fifth year (when aged 16-17) after which it is possible for them to gain entry to university. However, many do not achieve the required grades and remain at school for sixth year. Even among those that do achieve the necessary grades it is common to remain at school and undertake further study (i.e. other subjects or Advanced Highers) and then start university at the same time as their friends and peers.
At universities in the United Kingdom and Ireland the term "fresher" is used to describe new students who are just beginning their first year. It would be unusual to call someone a fresher after their first few weeks at University. There is little derogatory connotation to this name in the UK, except for an occasional reference to "freshers" in a tone that implies naivety. More commonly, it will be used in a kindly fashion. For instance, a University official might ask a student if they are a fresher without any hint of a put down.
The term "first year" is the more commonly used, and connotation free, term for students in their first year. The week at the start of a new year is called "Freshers' Week", with a programme of special events to welcome new students; some universities, however, are attempting to drop the connotative associations of "freshers' week" by renaming it "welcome week".[citation needed] An undergraduate in the last year of study before graduation is generally known as a "finalist", or simply a third year (in England, Wales, and Northern Ireland ) or a fourth year (in Scotland and the Republic of Ireland).
A student in the United Kingdom
The ancient Scottish University of St Andrews uses the terms "bejant" for a first year (from the French "bec-jaune" – "yellow beak", "fledgling"). Second years are called "semi-bejants", third years are known as "tertians", and fourth years, or others in their final year of study, are called "magistrands".
For pupils, first of all is primary school and it starts off with Reception (similar to Kindergarten) and then move on to "year one, Year two" and so on until "year six". Children join secondary school in year 7 (when they are 11-12 year olds) up to year 11 and then after is sixth form, whereas a student entering a fee-paying school (usually a year later) would join the "third form"- equivalent to year 9- many schools have an alternate name for first years, some with a derogatory basis, but in others acting merely as a description- for example "shells"(non-derogatory) or "grubs"(derogatory.)
[edit] United States
[edit] Before first year
Some schools use the term "prefrosh" or "pre-frosh" to describe their newly admitted students. Schools often offer a campus preview weekend for prefroshes to know the schools better. A student is considered a prefrosh until he or she registers for the first class.
[edit] First year
A freshman (slang alternatives that are usually derogatory in nature include "fish", "fresher", "frosh", "newbie", "freshie", "snotter", "fresh-meat", etc.) is a first-year student in college, university or high school. The less-common[citation needed] gender-neutral synonym "first-year student" exists; the variation "freshperson" is rare.[citation needed]
In many traditions there is a remainder of the ancient (boarding, pre-commuting) tradition of fagging. He may also be subjected to a period of hazing or ragging as a pledge(r) or rookie, especially if joining a fraternity/sorority or certain other clubs, mainly athletic teams. For example, many high schools have initiation methods for freshmen, including, but not limited to, Freshman Duct-taped Throw, Freshman races, Freshman Orientation, Freshman Freshening (referring to poor hygiene among freshmen), and the Freshman Spread.
Even after that, specific rules may apply depending on the school's traditions (e.g., wearing a distinctive beanie), non-observance of which may result in punishment in which the paddle may come into play.
[edit] Second year
In the U.S., a sophomore is a second-year student. Folk etymology has it that the word means "wise fool"; consequently "sophomoric" means "pretentious, bombastic, inflated in style or manner; immature, crude, superficial" (according to the Oxford English Dictionary). It appears to be most likely formed from Greek "sophos", meaning "wise", and "moros" meaning "foolish", although it may also have separately originated from the word "sophumer", an obsolete variant of "sophism"[1]. Outside of the U.S. the term "sophomore" is rarely used, with second-year students simply called "second years".
Academic procession during the University of Canterbury graduation ceremony.
[edit] Post-second year
In the U.S. a "junior" is a student in the penultimate (usually third) year and a "senior" a student in the last (usually fourth) year of college, university, or high school. A college student who takes more than the normal number of years to graduate is sometimes referred to as a "super senior".[2] The term "underclassman" is used to refer collectively to freshmen and sophomores, and "upperclassman" to refer collectively to juniors and seniors, sometimes even sophomores. The term "middler" is used to describe a third-year student of a school (generally college) which offers five years of study. In this situation, the fourth and fifth years would be referred to as "junior" and "senior" years, respectively.
[edit] Mature students
Main article: Mature student
A mature, or adult student in tertiary education (at a university or a college) is normally classified as an (undergraduate) student who is at least 21 - 23 years old at the start of their course and usually having been out of the education system for at least two years. Mature students can also include students who have been out of the education system for decades, or students with no secondary education. Mature students also make up graduate and postgraduate populations by demographic of age.
[edit] Student pranks
Main article: Student prank
University students have a long association with pranks and japes.[3][4][5][6][7] These can often involve petty crime, such as the theft of traffic cones and other public property,[8] or hoaxes. It is also not uncommon for students from one school to steal or deface the mascot of a rival school.[9] In fact, pranks play such a significant part in student culture that numerous books have been published that focus on the issue.[10][11]Pranks may reflect current events[12], be a form of protest or revenge, or have no other purpose than for the enjoyment of the prank itself. A recent report has been released focusing on the misbehaviour of university students. The report, Studentification: A Guide to Opportunities, Challenges and Practice, by Universities UK, focuses on six British universities as case studies.
[edit] Other terms
A student who is repeating a grade level of schooling due to poor grades is sometimes referred to as having been "held back".
The term pupil (originally a Latin term for a minor as the ward of an adult guardian etc.) is used in British primary and secondary schools instead of "student", but once attending higher education such as sixth-form college etc, the term "student" is standard.
The United States military academies use only numerical terms, except there are colloquial expressions used in everyday speech. In order from first year to fourth year, students in these institutions are officially referred to as "fourth-class", "third-class", "second-class", and "first-class" cadets or midshipmen. Unofficially, other terms are used, for example at the United States Military Academy, freshman are called "plebes," sophomores are called "yearlings" or "yuks," juniors are called "cows," and seniors are called "firsties." Some universities also use numerical terms to identify classes; students enter as "first-years" and graduate as "fourth-years" (or, in some cases, "fifth-years", "sixth-years", etc).
Freshers' Flu refers to the generic illness that many new students get during the first few weeks of starting the first year. This is often attributed to viral/bacterial diseases being carried by students from other regions of the country/world, to which some have no immunity.[citation needed]
In the United States a "gunner" is an overly competitive student, typically in law school or medical school. Calling someone a gunner is usually highly offensive[citation needed]. A gunner is also overly ambitious and often excitedly volunteers oral answers in class that are, by turns, incorrect, off-topic, or specifically designed to demonstrate the questionable "intellectual" prowess of the person supplying them. These questions are often prefaced with phrases like "A cursory literature search revealed ... " A gunner will compromise his or her peer relationships in order to obtain recognition and praise from his or her instructors and superiors, often by directly harming or attempting to harm the academic well-being of said peers.[13]
[edit] Idiomatic use
"Freshman" and "sophomore" are sometimes used figuratively, almost exclusively in the United States, to refer to a first or second effort ("the singer's sophomore album"), or to a politician's first or second term in office ("freshman senator") or an athlete's first or second year on a professional sports team. "Junior" and "senior" are not used in this figurative way to refer to third and fourth years or efforts, because of those words' broader meanings of "younger" and "older". (A junior senator is therefore not one who is in his or her third term of office, but merely one who has not been in the Senate as long as the other senator from his or her state.)
Saturday, October 18, 2008
ENTRY 17
Work
From Wikipedia, the free encyclopedia
Jump to: navigation, search
"Arbeit" redirects here. For the French music project, see Arbeit!.
Look up work in Wiktionary, the free dictionary.
Work may refer to:
Mechanical work, the amount of energy transferred by a force
Work (thermodynamics), the quantity of energy transferred from one system to another
"Work", one's place of employment
WORK (FM), an American FM radio station licensed to serve Barre, Vermont
Labour (economics), measure of the work done by human beings
Wage labour, in which a worker sells their labour and the employer buys it
Manual labour, physical work done by people
Work of art, a creation, such as a song or a painting
Work (project management), the effort applied to produce a deliverable or accomplish a task
Work (professional wrestling), a staged event
Sex work, employment in the sex industry.
Work (Kelly Rowland song), a single by Kelly Rowland
Work (Jars of Clay song), a song by Jars of Clay
Work (Jimmy Eat World song), a song by rock band Jimmy Eat World
Work (Ciara song), a single by Ciara
Work (1915 film), a 1915 silent film co-starring Edna Purviance
Work Records (aka "WORK" or "The WORK Group"), a music label under Sony Records
Work 1989-2002, a release by the electronic music duo Orbital
Work (painting), by Ford Madox Brown
Work: A Story of Experience, a novel by Louisa May Alcott
Work: EU-OSHA, European Agency for Safety and Health at Work
Working may refer to:
Working (musical), a 1978 musical
Working (TV series), a situation comedy
Working (book), a book by Studs Terkel
Holbrook Working a statistician and economist
From Wikipedia, the free encyclopedia
Jump to: navigation, search
"Arbeit" redirects here. For the French music project, see Arbeit!.
Look up work in Wiktionary, the free dictionary.
Work may refer to:
Mechanical work, the amount of energy transferred by a force
Work (thermodynamics), the quantity of energy transferred from one system to another
"Work", one's place of employment
WORK (FM), an American FM radio station licensed to serve Barre, Vermont
Labour (economics), measure of the work done by human beings
Wage labour, in which a worker sells their labour and the employer buys it
Manual labour, physical work done by people
Work of art, a creation, such as a song or a painting
Work (project management), the effort applied to produce a deliverable or accomplish a task
Work (professional wrestling), a staged event
Sex work, employment in the sex industry.
Work (Kelly Rowland song), a single by Kelly Rowland
Work (Jars of Clay song), a song by Jars of Clay
Work (Jimmy Eat World song), a song by rock band Jimmy Eat World
Work (Ciara song), a single by Ciara
Work (1915 film), a 1915 silent film co-starring Edna Purviance
Work Records (aka "WORK" or "The WORK Group"), a music label under Sony Records
Work 1989-2002, a release by the electronic music duo Orbital
Work (painting), by Ford Madox Brown
Work: A Story of Experience, a novel by Louisa May Alcott
Work: EU-OSHA, European Agency for Safety and Health at Work
Working may refer to:
Working (musical), a 1978 musical
Working (TV series), a situation comedy
Working (book), a book by Studs Terkel
Holbrook Working a statistician and economist
Friday, October 17, 2008
ENTRY 16
The Seven Habits of Highly Effective People
From Wikipedia, the free encyclopedia
Jump to: navigation, search
The Seven Habits of Highly Effective People
Author
Stephen R. W. Covey
Subject(s)
Self help
Publisher
Free Press
Publication date
1989
ISBN
ISBN 0-7432-6951-915th annv. paper
Followed by
The 8th Habit: From Effectiveness to Greatness
The Seven Habits of Highly Effective People, first published in 1989, is a self-help book written by Stephen R. Covey. It has sold over 15 million copies in 38 languages since first publication, which was marked by the release of a 15th anniversary edition in 2004. The book lists seven principles that, if established as habits, are supposed to help a person achieve true interdependent effectiveness. Covey argues this is achieved by aligning oneself to what he calls "true north" principles of a character ethic that he believes to be universal and timeless.
The book was enormously popular, and catapulted Covey into lucrative public-speaking appearances and workshops. He has also written a number of follow-up books, such as The Power Of The 7 Habits: Applications And Insights; Seven Habits of Highly Effective Families; and Beyond the Seven Habits. A sequel to The Seven Habits is The 8th Habit: From Effectiveness to Greatness published in 2004.
Also, Sean Covey (Stephen's son) has written a version for teens, The Seven Habits of Highly Effective Teens. This version simplifies the 7 Habits for younger readers so they can better understand them. In October 2006, Sean Covey also published The 6 Most Important Decisions You Will Ever Make: A Guide for Teens. This guide highlights key times in the life of a teen and gives advice on how to deal with them. Stephen Covey's oldest son, Stephen M.R. Covey, has written a book titled The Speed of Trust.
A course based on The Seven Habits is offered through FranklinCovey and at many corporations and government agencies, such as the Regional Community Policing Institute-California, (www.rcpi-ca.org), United States Department of Homeland Security's Federal Law Enforcement Training Center. [1]
[edit] A Principled Approach
Throughout the book, Covey points to principles as the focus. The book presents the principles as an approach rather than a set of behaviors. The book imparts the principles in four sections.
Paradigms and Principles: Covey lays the basic foundation for the creation of the habits.
Private Victory: The first three habits are intended to teach a person how to move out of a state of dependence and beyond a state of independence. Covey refers to his ideal state as interdependence, which begins with the creation and manifestation of a highly developed sense of personal values and goals.
Public Victory: Habits four through six complete the steps that lead to interdependence by showing how to align one's needs and desires with those of other people and create effective relationships.
Renewal: In the final section, Covey directs the reader to begin a process of self-improvement.
[edit] The Seven Habits
The chapters are dedicated to each of the habits, which are represented by the following imperatives:
Be Proactive. Here, Covey emphasizes the original sense of the term "proactive" as coined by Victor Frankl. You can either be proactive or reactive when it comes to how you respond to certain things. When you are reactive, you blame other people and circumstances for obstacles or problems. Being proactive means taking responsibility for every aspect of your life. Initiative and taking action will then follow. Covey also argues that man is different from other animals in that he has self-consciousness. He has the ability to detach himself and observe his own self; think about his thoughts. He goes on to say how this attribute enables him: It gives him the power not to be affected by his circumstances. Covey talks about stimulus and response. Between stimulus and response, we have the power of free will to choose our response.
Begin with the End In Mind. This chapter is about setting long-term goals based on "true north" principles. Covey recommends formulating a "personal vision statement" to document one's perception of one's own vision in life. He sees visualization as an important tool to develop this. He also deals with organizational vision statements, which he claims to be more effective if developed and supported by all members of an organization rather than prescribed.
Put First Things First. Here, Covey describes a framework for prioritizing work that is aimed at short-term goals, at the expense of tasks that appear not to be urgent, but are in fact very important. Delegation is presented as an important part of time management. Successful delegation, according to Covey, focuses on results and benchmarks that are to be agreed upon in advance, rather than prescribed as detailed work plans.
Think Win/Win describes an attitude whereby mutually beneficial solutions are sought that satisfy the needs of oneself, or, in the case of a conflict, both parties involved.
Seek First to Understand, Then to be Understood. Covey warns that giving out advice before having empathetically understood a person and their situation will likely result in rejection of that advice. Thoroughly reading out your own autobiography will decrease the chance of establishing a working communication.
Synergize describes a way of working in teams. Apply effective problem solving. Apply collaborative decision making. Value differences. Build on divergent strengths. Leverage creative collaboration. Embrace and leverage innovation. It is put forth that when synergy is pursued as a habit, the result of the teamwork will exceed the sum of what each of the members could have achieved on their own. “The whole is greater than the sum of its parts.”
Sharpen the saw focuses on balanced self-satisfaction: Regain what Covey calls "production capability" by engaging in carefully selected recreational activities
From Wikipedia, the free encyclopedia
Jump to: navigation, search
The Seven Habits of Highly Effective People
Author
Stephen R. W. Covey
Subject(s)
Self help
Publisher
Free Press
Publication date
1989
ISBN
ISBN 0-7432-6951-915th annv. paper
Followed by
The 8th Habit: From Effectiveness to Greatness
The Seven Habits of Highly Effective People, first published in 1989, is a self-help book written by Stephen R. Covey. It has sold over 15 million copies in 38 languages since first publication, which was marked by the release of a 15th anniversary edition in 2004. The book lists seven principles that, if established as habits, are supposed to help a person achieve true interdependent effectiveness. Covey argues this is achieved by aligning oneself to what he calls "true north" principles of a character ethic that he believes to be universal and timeless.
The book was enormously popular, and catapulted Covey into lucrative public-speaking appearances and workshops. He has also written a number of follow-up books, such as The Power Of The 7 Habits: Applications And Insights; Seven Habits of Highly Effective Families; and Beyond the Seven Habits. A sequel to The Seven Habits is The 8th Habit: From Effectiveness to Greatness published in 2004.
Also, Sean Covey (Stephen's son) has written a version for teens, The Seven Habits of Highly Effective Teens. This version simplifies the 7 Habits for younger readers so they can better understand them. In October 2006, Sean Covey also published The 6 Most Important Decisions You Will Ever Make: A Guide for Teens. This guide highlights key times in the life of a teen and gives advice on how to deal with them. Stephen Covey's oldest son, Stephen M.R. Covey, has written a book titled The Speed of Trust.
A course based on The Seven Habits is offered through FranklinCovey and at many corporations and government agencies, such as the Regional Community Policing Institute-California, (www.rcpi-ca.org), United States Department of Homeland Security's Federal Law Enforcement Training Center. [1]
[edit] A Principled Approach
Throughout the book, Covey points to principles as the focus. The book presents the principles as an approach rather than a set of behaviors. The book imparts the principles in four sections.
Paradigms and Principles: Covey lays the basic foundation for the creation of the habits.
Private Victory: The first three habits are intended to teach a person how to move out of a state of dependence and beyond a state of independence. Covey refers to his ideal state as interdependence, which begins with the creation and manifestation of a highly developed sense of personal values and goals.
Public Victory: Habits four through six complete the steps that lead to interdependence by showing how to align one's needs and desires with those of other people and create effective relationships.
Renewal: In the final section, Covey directs the reader to begin a process of self-improvement.
[edit] The Seven Habits
The chapters are dedicated to each of the habits, which are represented by the following imperatives:
Be Proactive. Here, Covey emphasizes the original sense of the term "proactive" as coined by Victor Frankl. You can either be proactive or reactive when it comes to how you respond to certain things. When you are reactive, you blame other people and circumstances for obstacles or problems. Being proactive means taking responsibility for every aspect of your life. Initiative and taking action will then follow. Covey also argues that man is different from other animals in that he has self-consciousness. He has the ability to detach himself and observe his own self; think about his thoughts. He goes on to say how this attribute enables him: It gives him the power not to be affected by his circumstances. Covey talks about stimulus and response. Between stimulus and response, we have the power of free will to choose our response.
Begin with the End In Mind. This chapter is about setting long-term goals based on "true north" principles. Covey recommends formulating a "personal vision statement" to document one's perception of one's own vision in life. He sees visualization as an important tool to develop this. He also deals with organizational vision statements, which he claims to be more effective if developed and supported by all members of an organization rather than prescribed.
Put First Things First. Here, Covey describes a framework for prioritizing work that is aimed at short-term goals, at the expense of tasks that appear not to be urgent, but are in fact very important. Delegation is presented as an important part of time management. Successful delegation, according to Covey, focuses on results and benchmarks that are to be agreed upon in advance, rather than prescribed as detailed work plans.
Think Win/Win describes an attitude whereby mutually beneficial solutions are sought that satisfy the needs of oneself, or, in the case of a conflict, both parties involved.
Seek First to Understand, Then to be Understood. Covey warns that giving out advice before having empathetically understood a person and their situation will likely result in rejection of that advice. Thoroughly reading out your own autobiography will decrease the chance of establishing a working communication.
Synergize describes a way of working in teams. Apply effective problem solving. Apply collaborative decision making. Value differences. Build on divergent strengths. Leverage creative collaboration. Embrace and leverage innovation. It is put forth that when synergy is pursued as a habit, the result of the teamwork will exceed the sum of what each of the members could have achieved on their own. “The whole is greater than the sum of its parts.”
Sharpen the saw focuses on balanced self-satisfaction: Regain what Covey calls "production capability" by engaging in carefully selected recreational activities
Thursday, October 16, 2008
ENTRY 15
Sleep
From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Sleep (disambiguation).
"Waking up" redirects here. For other uses, see Waking Up.
Emily Gibbons in Tehran, Iran
Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish. In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies — regular sleep is essential for survival.[1] However, its purposes are only partly clear and are the subject of intense research.[2]Physiology
In mammals and birds the measurement of eye movement during sleep is used to divide sleep into the two broad types of Rapid Eye Movement (REM) and Non-Rapid Eye Movement (NREM) sleep. Each type has a distinct set of associated physiological, neurological and psychological features.
Sleep proceeds in cycles of REM and the four stages of NREM, the order normally being:
stages 1 -> 2 -> 3 -> 4 -> 3 -> 2 -> REM.
In humans this cycle is on average 90 to 110 minutes,[3] with a greater amount of stages 3 and 4 early in the night and more REM later in the night. Each phase may have a distinct physiological function. Drugs such as sleeping pills and alcoholic beverages can suppress certain stages of sleep (see Sleep deprivation). This can result in a sleep that exhibits loss of consciousness but does not fulfill its physiological functions.
Allan Rechtschaffen and Anthony Kales originally outlined the criteria for identifying the stages of sleep in 1968. The American Academy of Sleep Medicine (AASM) updated the staging rules in 2007.
Stage 4 Sleep. EEG highlighted by red box.
REM Sleep. EEG highlighted by red box. Eye movements highlighted by red line.
[edit] Stages of sleep
Criteria for REM sleep include not only rapid eye movements but also a rapid low voltage EEG. In mammals, at least, low muscle tone is also seen. Most memorable dreaming occurs in this stage. NREM accounts for 75–80% of total sleep time in normal human adults. In NREM sleep, there is relatively little dreaming. Non-REM encompasses four stages; stages 1 and 2 are considered 'light sleep', and 3 and 4 'deep sleep' or slow-wave sleep, SWS. They are differentiated solely using EEG, unlike REM sleep which is characterized by rapid eye movements and relative absence of muscle tone. In non-REM sleep there are often limb movements, and parasomnias such as sleepwalking may occur. A cyclical alternating pattern may sometimes be observed during a stage.
NREM consists of four stages according to the 2007 AASM standards:
During Stage N1 the brain transitions from alpha waves (having a frequency of 8 to 13 Hz, common to people who are awake) to theta waves (frequency of 4 to 7 Hz). This stage is sometimes referred to as somnolence, or "drowsy sleep". Associated with the onset of sleep during N1 may be sudden twitches and hypnic jerks also known as positive myoclonus. Some people may also experience hypnagogic hallucinations during this stage, which can be more troublesome to the subject. During N1 the subject loses some muscle tone and conscious awareness of the external environment.
Stage N2, is characterized by "sleep spindles" (12 to 16 Hz) and "K-complexes." During this stage, muscular activity as measured by electromyography (EMG) lowers and conscious awareness of the external environment disappears. This stage occupies 45 to 55% of total sleep.
In Stage N3, the delta waves (0.5 to 4 Hz), also called delta rhythms, make up less than 50% of the total wave-patterns. This is considered part of deep or slow-wave sleep (SWS) and appears to function primarily as a transition into stage N4. This is the stage in which night terrors, bedwetting, sleepwalking and sleep-talking occur.
In Stage N4, delta-waves make up more than 50% of the wave-patterns. Stages N3 and N4 are the deepest forms of sleep; N4 is effectively a deeper version of N3, in which the deep-sleep characteristics, such as delta-waves, are more pronounced. As of new AASM guidelines, the determination between stage 3 and stage 4 sleep is inconsequential and both may be considered delta sleep or slow wave sleep. Therefore, in a recent ruling by the AASM, in order to make precision the scoring guidelines, stage four had been disbanded, and left is the stage of sleep N3 to describe the delta sleep attributed to it.[4]
Both REM sleep and NREM sleep stages 3 and 4 are homeostatically driven; that is, if a person or animal is selectively deprived of one of these, it rebounds once uninhibited sleep again is allowed. This suggests that both are essential to the functions of the sleep process.
[edit] Sleep timing
Sleep timing is controlled by the circadian clock, by homeostasis and, in humans, by willed behavior. The circadian clock, an inner time-keeping, temperature-fluctuating, enzyme-controlling device, works in tandem with adenosine, a neurotransmitter which inhibits many of the bodily processes that are associated with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. The timing is affected by one's chronotype. It is the circadian rhythm which determines the ideal timing of a correctly structured and restorative sleep episode.[5]
Homeostatic sleep propensity, the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode, is also important and must be balanced against the circadian element for satisfactory sleep. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep.[6] Sleep offset, awakening, is primarily determined by circadian rhythm. A normal person who regularly awakens at an early hour will generally not be able to sleep much later than the person's normal waking time, even if moderately sleep deprived.
[edit] Optimal amount in humans
[edit] Adults
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day. The timing is correct when the following two circadian markers occur after the middle of the sleep episode but before awakening:[7]
maximum concentration of the hormone melatonin, and
minimum core body temperature.
The National Sleep Foundation in the United States maintains that eight to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory and problem solving, and overall health, as well as reducing the risk of accidents.[8] A widely publicized 2003 study[9] performed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with fewer than eight hours of sleep.
However, a University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night.[10] Another study of sleep duration and mortality risk in women showed similar results.[11] Other studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality", though this study suggests the cause is probably other factors such as depression and socio-economic status which would correlate statistically. [12] It has been suggested that the correlation between lower sleep hours and reduced morbidity only occurs with those who wake after less sleep naturally, rather than those who use an alarm.
A Koli Wada woman sleeping in Nirona village
Causal links are currently speculative: the available data may only reflect comorbid depression, socioeconomic status, or even alcohol use, for example.[13] These studies cannot be used to determine optimal sleep habits, only correlation — and empirically observed correlation is a necessary but not sufficient condition for causality. A need for nine or ten hours of sleep a day, or only five to six, may or may not have the same cause as the shortened life span. In other words, long or short sleep duration itself has not been shown to be a cause of early death.
Researchers from the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death.[14][15] Professor Francesco Cappuccio said: “Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality but in contrast to the short sleep-mortality association it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue. [...] In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose to ill-health.”
Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism and bipolar disorder. Up to 90% of patients with depression are found to have sleep difficulties.[citation needed]
[edit] Hours by age
A child sleeping
Children need a greater amount of sleep per day than adults to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.[8][6] A newborn baby spends almost half of its sleep time in REM-sleep. By the age of five or so, only a bit over two hours are spent in REM.[16]
Age
Average amount of sleep per day
Newborn
up to 18 hours
1-12 months
14–18 hours
1-3 years
12-15 hours
3-5 years
11-13 hours
5-12 years
9-11 hours
Adolescents
9-10 hours
Adults, including elderly
7-8 (+) hours
Pregnant women
8 (+) hours
[edit] Sleep debt
Main article: Sleep debt
Sleep debt is the effect of not getting quite enough rest and sleep; a large debt causes mental, emotional and physical fatigue. It is unclear why a lack of sleep causes irritability however theories are emerging that suggest if the body produces insufficient cortisol during stage 3 and 4 sleep it can have negative effects on our alertness and emotions during the day.[citation needed]
Scientists do not agree on how much sleep debt it is possible to accumulate, whether it is accumulated against an individual's average sleep or some other benchmark, nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is likely that children are sleeping less than previously in Western societies.[17]
[edit] Functions
The multiple theories proposed to explain the function of sleep reflect the as yet incomplete understanding of the subject.
It is likely that sleep evolved to fulfill some primeval function, but has taken over multiple functions over time as organisms have evolved. An analogy would be that to the larynx, which performs multiple functions, such as controlling the passage of food and air, phonation for communicating and social purposes, etc. These are all functions of the larynx, but just one of them likely represents the original function. Some of the many proposed functions of sleep are as follows:
[edit] Restoration
Wound healing has been shown to be affected by sleep. A study conducted by Gumustekin et al.[18] in 2004 shows sleep deprivation hindering the healing of burns on rats.
It has also been shown that sleep deprivation affects the immune system and metabolism. In a study by Zager et al in 2007,[19] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats' blood tests indicated a 20% decrease in white blood cell count, a significant change in the immune system.
A study by Bonnet and Arand[20] in 2003 indicates that sleep affects metabolism, is indeed a metabolic phase - anabolism. Comparing normal human sleepers and sleepers with sleep state misperception insomnia, where patients complain of poor sleep but have normal sleep by electroencephalographic (EEG) criteria, the researchers found significantly greater metabolism values for the normal sleepers.
It has yet to be clearly proven that sleep duration affects somatic growth. One study by Jenni et al[21] in 2007 recorded growth, height and weight, as correlated to parent-reported time-in-bed in 305 children over a period of nine years (age 1-10). It was found that "the variation of sleep duration among children does not seem to have an effect on growth". It has been shown that sleep, more specifically slow-wave sleep (SWS), does affect growth hormone levels in adult men. During eight hours sleep, Van Cauter, Leproult, and Plat[22] found that the men with a high percentage of SWS (average 24%) also had high growth hormone secretion, while subjects with a low percentage of SWS (average 9%) had low growth hormone secretion.
There are multiple arguments supporting the restorative function of sleep. We are rested after sleeping and it is natural to assume that this is a basic purpose of sleep. The metabolic phase during sleep is anabolic; anabolic hormones such as growth hormones as mentioned above are secreted preferentially during sleep. Sleep among species is, in general, inversely related to the animal size and basal metabolic rate. Rats with a very high basal metabolic rate sleep for up to 14 hours a day whereas elephants and giraffes with lower BMRs sleep only 3-4 hours per day.
Energy conservation could as well have been accomplished by resting quiescent without shutting off the organism from the environment, potentially a dangerous situation. A sedentary non-sleeping animal is more likely to survive predators, while still preserving energy. Sleep therefore does something else other than conserving energy. Most interestingly, hibernating animals that wake up from hibernation go into rebound sleep because of lack of sleep during the hibernation period. They are definitely well rested and are conserving energy during hibernation, but need sleep for something else.[23] Rats kept awake indefinitely develop skin lesions, hyperphagia, loss of body mass, hypothermia, and eventually septicemia and death.[24]
[edit] Anabolic/catabolic
Non-REM sleep may be an anabolic state marked by physiological processes of growth and rejuvenation of the organism's immune, nervous, muscular, and skeletal systems (with some exceptions). Wakefulness may perhaps be viewed as a cyclical, temporary, hyperactive catabolic state during which the organism acquires nourishment and reproduces.
[edit] Ontogenesis
According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism (Marks et al., 1995). Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass (Mirmiran et al. 1983), and an abnormal amount of neuronal cell death (Morrissey, Duntley & Anch, 2004).
REM sleep appears to be important for development of the brain. REM sleep occupies majority of time of sleep of infants, which spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses yet without any motor consequences which may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.
However, this does not explain why older adults still need REM sleep. Aquatic mammal infants do not have REM sleep in infancy [25] REM sleep in those animals increases as they age.
[edit] Memory processing
Scientists have shown numerous ways in which sleep is related to memory. In a study conducted by Turner, Drummond, Salamat, and Brown[26] working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. Turner et al. allowed 18 women and 22 men to sleep only 26 minutes per night over a 4-day period. Subjects were given initial cognitive tests while well rested and then tested again twice a day during the 4 days of sleep deprivation. On the final test the average working memory span of the sleep deprived group had dropped by 38% in comparison to the control group.
Memory also seems to be affected differently by certain stages of sleep such as REM and slow-wave sleep (SWS). In one study cited in Born, Rasch, and Gais[27] multiple groups of human subjects were used: wake control groups and sleep test groups. Sleep and wake groups were taught a task and then tested on it both on early and late nights, with the order of nights balanced across participants. When the subjects' brains were scanned during sleep, hypnograms revealed that SWS was the dominant sleep stage during the early night representing around 23% on average for sleep stage activity. The early night test group performed 16% better on the declarative memory test than the control group. During late night sleep, REM became the most active sleep stage at about 24%, and the late night test group performed 25% better on the procedural memory test than the control group. This indicates that procedural memory benefits from late REM-rich sleep whereas declarative memory benefits from early SWS-rich sleep.
Another study conducted by Datta[28] indirectly supports these results. The subjects chosen were 22 male rats. A box was constructed where a single rat could move freely from one end to the other. The bottom of the box was made of a steel grate. A light would shine in the box accompanied by a sound. After a 5 second delay an electrical shock would be applied. Once the shock commenced the rat could move to the other end of the box, ending the shock immediately. The rat could also use the 5-second delay to move to the other end of the box and avoid the shock entirely. The length of the shock never exceeded 5 seconds. This was repeated 30 times for half the rats. The other half, the control group, was placed in the same trial but the rats were shocked regardless of their reaction. After each of the training sessions the rat would be placed in a recording cage for 6 hours of polygraphic recordings. This process was repeated for 3 consecutive days. This study found that during the post-trial sleep recording session rats spent 25.47% more time in REM sleep after learning trials than after control trials. These trials support the results of the Born et al. study, indicating an obvious correlation between REM sleep and procedural knowledge.
Another interesting observation of the Datta study is that the learning group spent 180% more time in SWS than did the control group during the post-trial sleep-recording session. This phenomenon is supported by a study performed by Kudrimoti, Barnes, and McNaughton.[29] This study shows that after spatial exploration activity, patterns of hippocampal place cells are reactivated during SWS following the experiment. In a study by Kudrimoti et al. seven rats were run through a linear track using rewards on either end. The rats would then be placed in the track for 30 minutes to allow them to adjust (PRE), then they ran the track with reward based training for 30 minutes (RUN), and then they were allowed to rest for 30 minutes. During each of these three periods EEG data were collected for information on the rats’ sleep stages. Kudrimoti et al. computed the mean firing rates of hippocampal place cells during pre-behavior SWS (PRE) and three 10-minute intervals in post-behavior SWS (POST) by averaging across 22 track-running sessions from seven rats. The results showed that 10 minutes after the trial RUN session there was a 12% increase in the mean firing rate of hippocampal place cells from the PRE level, however after 20 minutes the mean firing rate returned rapidly toward the PRE level. The elevated firing of hippocampal place cells during SWS after spatial exploration could explain why there were elevated levels of SWS sleep in Datta’s study as it also dealt with a form of spatial exploration.
The different studies all suggest that there is a correlation between sleep and the many complex functions of memory. Harvard sleep researchers Saper and Stickgold[30] point out that an essential part of memory and learning consists of nerve cell dendrites sending information to the cell body to be organized into new neuronal connections. This process demands that no external information is presented to these dendrites, and they suggest that this may be why it is during sleep that we solidify memories and organize knowledge.
Further information: Sleep and learning, Sleep and creativity
[edit] Preservation
The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the person during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats. (Allison & Cicchetti, 1976; Webb, 1982).
However, this theory fails to explain why the brain disengages from the external environment during normal sleep. Another argument against the theory is that sleep is not simply a passive consequence of removing the animal from the environment, but is a "drive": animals alter their behaviors in order to obtain sleep. Therefore, circadian regulation is more than sufficient to explain periods of activity and quiescence that are adaptive to an organism, but the more peculiar specializations of sleep probably serve different and unknown functions.
Moreover, the preservation theory does not explain why carnivores like lions, which are on top of the food chain, sleep the most. By the preservation logic, these top carnivores should not need any sleep at all. Preservation does not explain why aquatic mammals sleep while moving. Lethargy during these vulnerable hours would do the same, and will be more advantageous because the animal will be quiescent but still be able to respond to environmental challenges like predators etc. Sleep rebound that occurs after a sleepless night will be maladaptive, but still occurs for a reason. For example, a zebra falling asleep the day after it spent the sleeping time running from a lion is more and not less vulnerable to predation.
[edit] Dreaming
Main article: Dream
Dreaming is the perception of sensory images and sounds during sleep, in a sequence which the sleeper/dreamer usually perceives more as an apparent participant than an observer. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep.
People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconscious, and he used dream interpretation in the form of psychoanalysis to uncover these desires. Scientists have become skeptical about the Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. See Freud: The Interpretation of Dreams
Rosalind Cartwright stated that
One Function of dreams may be to restore our sense of competence.... it is also probable that in many times of stress, dreams have more work to do in resolving our problems and are thus more salient and memorable.[31]
– Rosalind Cartwright, The Sunday Observer
J. Allan Hobson's and Robert McCarley's activation synthesis theory proposes that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period. According to the theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it; hence the odd nature of many dreams.[32]
[edit] Effect of food and drink on sleep
[edit] Depressants
Tryptophan
The amino acid tryptophan is a building block of the protein found in foods. It contributes to sleepiness. Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals containing tryptophan tend to cause drowsiness. Tryptophan is a precursor to the neurotransmitter serotonin, which is a precursor to the neurohormone melatonin (see below).
Melatonin
Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. Melatonin supplementation may be used as a sleep aid, both as a hypnotic and as a chronobiotic (see phase response curve, PRC).
5-hydroxy-tryptophan (5-HTP)
5-HTP, the precursor to serotonin (5-HT) can cause drowsiness when ingested.
The "Post-Lunch Dip"
Many people have a temporary drop in alertness in early afternoon, commonly known as the post-lunch dip. While a large meal, rich in carbohydrates, can make a person feel sleepy, the post-lunch dip is mostly an effect of the biological clock. People naturally feel most sleepy (have the greatest "drive for sleep") at two times of the day about 12 hours apart, for example at 2:00 AM and 2:00 PM. At those two times, the body clock "kicks in". At about 2 p.m. (14:00), it overrides the homeostatic build-up of sleep debt, allowing several more hours of wakefulness. At about 2 a.m. (02:00), with the daily sleep debt paid off, it "kicks in" again to ensure a few more hours of sleep.
Alcohol
Often people start drinking alcohol in order to get to sleep (alcohol is initially a sedative and will make you get to sleep faster). However, being addicted to alcohol can lead to disrupted sleep because alcohol has a rebound effect later in the night. As a result there is strong evidence linking alcoholism and insomnia.[citation needed]
Barbiturates
Barbiturates when taken cause drowsiness and have actions similar to ethanol (drinking alcohol).
[edit] Stimulants
Caffeine
Caffeine is a stimulant that works by slowing the action of the hormones in the brain that cause sleepiness. Effective dosage is individual, in part dependent on prior usage. It can cause a rapid reduction in alertness as it wears off.
Energy Drinks
The stimulating effects of energy drinks comes from natural stimulants such as caffeine, sugars, and essential amino acids, and eventually will create a rapid reduction in alertness similar to that of caffeine.
Amphetamines
Amphetamines (amphetamine, dextroamphetamine, methamphetamine, etc) are often used to treat narcolepsy and ADHD disorders, the most common effects are decreased appetite, stimulation and insomnia, and increased alertness.
Cocaine and Crack Cocaine
Similar in action to the amphetamines.
MDMA
Commonly known as ecstacy, users are kept awake similar to amphetamines with intense euphoria, includes other similar drugs like MDA, MMDA, or bk-MDMA.
Methylphenidate
Commonly known as Ritalin, similar in action to amphetamines and cocaine.
[edit] Causes of difficulty in sleeping
There are a great many possible reasons for sleeping poorly. Following sleep hygienic principles may solve problems of physical or emotional discomfort.[33] When pain, illness, drugs or stress are the culprit, the cause must be treated. Sleep disorders, including the sleep apneas, narcolepsy, primary insomnia, periodic limb movement disorder (PLMD), restless leg syndrome (RLS) and the circadian rhythm sleep disorders, are treatable.
Elderly people may to some degree lose the ability to consolidate sleep. They need the same amount per day as they've always needed, but may need to take some of their sleep as daytime naps.
[edit] Anthropology of sleep
Recent research suggests that sleep patterns vary significantly across human cultures.[34][35] The most striking differences are between societies that have plentiful artificial light and ones that do not. Cultures without artificial light have more broken-up sleep patterns. This is called polyphasic sleep or segmented sleep and has led to expressions such as "first sleep," "watch," and "second sleep" which appear in literature from all over the world.
Some cultures have fragmented sleep patterns in which people sleep at all times of the day, and for shorter periods at night. For example, many Mediterranean and Latin American cultures have a siesta, in which people sleep for a period in the afternoon. In many nomadic or hunter-gatherer societies people sleep off and on throughout the day or night depending on what is happening.[citation needed]
[edit] Sleep in non-humans
Sleeping Japanese Macaques.
Main article: Sleep (non-human)
Horses and other herbivorous ungulates can sleep while standing, but must necessarily lie down for REM sleep (which causes muscular atony) for short periods - giraffes, for example, only need to lie down for REM sleep for a few minutes at a time. Bats sleep while hanging upside down. Some aquatic mammals and some birds can sleep with one half of the brain, while the other half is awake, so called unihemispheric slow-wave sleep.[36] Birds and mammals have cycles of non-REM and REM sleep as described above for humans, though birds’ cycles are much shorter and they do not lose muscle tone (go limp) to the same extent that most mammals do.
Many animals sleep, but neurological sleep states are difficult to define in lower order animals. In these animals, sleep is defined using behavioral characteristics such as minimal movement, postures typical for the species and reduced responsiveness to external stimulation. Sleep is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer and/or deeper sleep. Herbivores, who require a long waking period to gather and consume their diet, typically sleep less each day than similarly sized carnivores who might well consume several days supply of meat in a setting.
Many species of mammals sleep for a large proportion of each 24-hour period when they are very young.[37] However, killer whales and some dolphins do not sleep during the first month of life.[38] Such differences may be explained by the ability of land mammal newborns to be easily protected by parents while sleeping, while marine animals must, even while very young, be more continuously vigilant for predators.
William C Dement in his book "The Promise of Sleep". states that the dolphin, originally a land mammal that has returned to the sea, maintains a numer of terrestrial traits including bearing their offspring alive and, unlike fish, breathing air. When terrestrial mammals breathe, they do so through an involuntary process similar to the one that causes our hearts to beat continuously. In dolphins the breathing process is under voluntary control throughout the day --- a process that, seemingly, would preclude sleep. In order to accomplish what seems to be an impossible task, dolphins allow one half of their brain to go to sleep while the other half remains awake. This is accomplished in two-hour cycles where one half of the brain is awake while the other half sleeps until the dolphin's day's sleep need has been fulfilled
From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Sleep (disambiguation).
"Waking up" redirects here. For other uses, see Waking Up.
Emily Gibbons in Tehran, Iran
Sleep is a natural state of bodily rest observed throughout the animal kingdom. It is common to all mammals and birds, and is also seen in many reptiles, amphibians and fish. In humans, other mammals, and a substantial majority of other animals which have been studied — such as fish, birds, ants, and fruit-flies — regular sleep is essential for survival.[1] However, its purposes are only partly clear and are the subject of intense research.[2]Physiology
In mammals and birds the measurement of eye movement during sleep is used to divide sleep into the two broad types of Rapid Eye Movement (REM) and Non-Rapid Eye Movement (NREM) sleep. Each type has a distinct set of associated physiological, neurological and psychological features.
Sleep proceeds in cycles of REM and the four stages of NREM, the order normally being:
stages 1 -> 2 -> 3 -> 4 -> 3 -> 2 -> REM.
In humans this cycle is on average 90 to 110 minutes,[3] with a greater amount of stages 3 and 4 early in the night and more REM later in the night. Each phase may have a distinct physiological function. Drugs such as sleeping pills and alcoholic beverages can suppress certain stages of sleep (see Sleep deprivation). This can result in a sleep that exhibits loss of consciousness but does not fulfill its physiological functions.
Allan Rechtschaffen and Anthony Kales originally outlined the criteria for identifying the stages of sleep in 1968. The American Academy of Sleep Medicine (AASM) updated the staging rules in 2007.
Stage 4 Sleep. EEG highlighted by red box.
REM Sleep. EEG highlighted by red box. Eye movements highlighted by red line.
[edit] Stages of sleep
Criteria for REM sleep include not only rapid eye movements but also a rapid low voltage EEG. In mammals, at least, low muscle tone is also seen. Most memorable dreaming occurs in this stage. NREM accounts for 75–80% of total sleep time in normal human adults. In NREM sleep, there is relatively little dreaming. Non-REM encompasses four stages; stages 1 and 2 are considered 'light sleep', and 3 and 4 'deep sleep' or slow-wave sleep, SWS. They are differentiated solely using EEG, unlike REM sleep which is characterized by rapid eye movements and relative absence of muscle tone. In non-REM sleep there are often limb movements, and parasomnias such as sleepwalking may occur. A cyclical alternating pattern may sometimes be observed during a stage.
NREM consists of four stages according to the 2007 AASM standards:
During Stage N1 the brain transitions from alpha waves (having a frequency of 8 to 13 Hz, common to people who are awake) to theta waves (frequency of 4 to 7 Hz). This stage is sometimes referred to as somnolence, or "drowsy sleep". Associated with the onset of sleep during N1 may be sudden twitches and hypnic jerks also known as positive myoclonus. Some people may also experience hypnagogic hallucinations during this stage, which can be more troublesome to the subject. During N1 the subject loses some muscle tone and conscious awareness of the external environment.
Stage N2, is characterized by "sleep spindles" (12 to 16 Hz) and "K-complexes." During this stage, muscular activity as measured by electromyography (EMG) lowers and conscious awareness of the external environment disappears. This stage occupies 45 to 55% of total sleep.
In Stage N3, the delta waves (0.5 to 4 Hz), also called delta rhythms, make up less than 50% of the total wave-patterns. This is considered part of deep or slow-wave sleep (SWS) and appears to function primarily as a transition into stage N4. This is the stage in which night terrors, bedwetting, sleepwalking and sleep-talking occur.
In Stage N4, delta-waves make up more than 50% of the wave-patterns. Stages N3 and N4 are the deepest forms of sleep; N4 is effectively a deeper version of N3, in which the deep-sleep characteristics, such as delta-waves, are more pronounced. As of new AASM guidelines, the determination between stage 3 and stage 4 sleep is inconsequential and both may be considered delta sleep or slow wave sleep. Therefore, in a recent ruling by the AASM, in order to make precision the scoring guidelines, stage four had been disbanded, and left is the stage of sleep N3 to describe the delta sleep attributed to it.[4]
Both REM sleep and NREM sleep stages 3 and 4 are homeostatically driven; that is, if a person or animal is selectively deprived of one of these, it rebounds once uninhibited sleep again is allowed. This suggests that both are essential to the functions of the sleep process.
[edit] Sleep timing
Sleep timing is controlled by the circadian clock, by homeostasis and, in humans, by willed behavior. The circadian clock, an inner time-keeping, temperature-fluctuating, enzyme-controlling device, works in tandem with adenosine, a neurotransmitter which inhibits many of the bodily processes that are associated with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. The timing is affected by one's chronotype. It is the circadian rhythm which determines the ideal timing of a correctly structured and restorative sleep episode.[5]
Homeostatic sleep propensity, the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode, is also important and must be balanced against the circadian element for satisfactory sleep. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep.[6] Sleep offset, awakening, is primarily determined by circadian rhythm. A normal person who regularly awakens at an early hour will generally not be able to sleep much later than the person's normal waking time, even if moderately sleep deprived.
[edit] Optimal amount in humans
[edit] Adults
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day. The timing is correct when the following two circadian markers occur after the middle of the sleep episode but before awakening:[7]
maximum concentration of the hormone melatonin, and
minimum core body temperature.
The National Sleep Foundation in the United States maintains that eight to nine hours of sleep for adult humans is optimal and that sufficient sleep benefits alertness, memory and problem solving, and overall health, as well as reducing the risk of accidents.[8] A widely publicized 2003 study[9] performed at the University of Pennsylvania School of Medicine demonstrated that cognitive performance declines with fewer than eight hours of sleep.
However, a University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night.[10] Another study of sleep duration and mortality risk in women showed similar results.[11] Other studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality", though this study suggests the cause is probably other factors such as depression and socio-economic status which would correlate statistically. [12] It has been suggested that the correlation between lower sleep hours and reduced morbidity only occurs with those who wake after less sleep naturally, rather than those who use an alarm.
A Koli Wada woman sleeping in Nirona village
Causal links are currently speculative: the available data may only reflect comorbid depression, socioeconomic status, or even alcohol use, for example.[13] These studies cannot be used to determine optimal sleep habits, only correlation — and empirically observed correlation is a necessary but not sufficient condition for causality. A need for nine or ten hours of sleep a day, or only five to six, may or may not have the same cause as the shortened life span. In other words, long or short sleep duration itself has not been shown to be a cause of early death.
Researchers from the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death.[14][15] Professor Francesco Cappuccio said: “Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality but in contrast to the short sleep-mortality association it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue. [...] In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose to ill-health.”
Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism and bipolar disorder. Up to 90% of patients with depression are found to have sleep difficulties.[citation needed]
[edit] Hours by age
A child sleeping
Children need a greater amount of sleep per day than adults to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.[8][6] A newborn baby spends almost half of its sleep time in REM-sleep. By the age of five or so, only a bit over two hours are spent in REM.[16]
Age
Average amount of sleep per day
Newborn
up to 18 hours
1-12 months
14–18 hours
1-3 years
12-15 hours
3-5 years
11-13 hours
5-12 years
9-11 hours
Adolescents
9-10 hours
Adults, including elderly
7-8 (+) hours
Pregnant women
8 (+) hours
[edit] Sleep debt
Main article: Sleep debt
Sleep debt is the effect of not getting quite enough rest and sleep; a large debt causes mental, emotional and physical fatigue. It is unclear why a lack of sleep causes irritability however theories are emerging that suggest if the body produces insufficient cortisol during stage 3 and 4 sleep it can have negative effects on our alertness and emotions during the day.[citation needed]
Scientists do not agree on how much sleep debt it is possible to accumulate, whether it is accumulated against an individual's average sleep or some other benchmark, nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is likely that children are sleeping less than previously in Western societies.[17]
[edit] Functions
The multiple theories proposed to explain the function of sleep reflect the as yet incomplete understanding of the subject.
It is likely that sleep evolved to fulfill some primeval function, but has taken over multiple functions over time as organisms have evolved. An analogy would be that to the larynx, which performs multiple functions, such as controlling the passage of food and air, phonation for communicating and social purposes, etc. These are all functions of the larynx, but just one of them likely represents the original function. Some of the many proposed functions of sleep are as follows:
[edit] Restoration
Wound healing has been shown to be affected by sleep. A study conducted by Gumustekin et al.[18] in 2004 shows sleep deprivation hindering the healing of burns on rats.
It has also been shown that sleep deprivation affects the immune system and metabolism. In a study by Zager et al in 2007,[19] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats' blood tests indicated a 20% decrease in white blood cell count, a significant change in the immune system.
A study by Bonnet and Arand[20] in 2003 indicates that sleep affects metabolism, is indeed a metabolic phase - anabolism. Comparing normal human sleepers and sleepers with sleep state misperception insomnia, where patients complain of poor sleep but have normal sleep by electroencephalographic (EEG) criteria, the researchers found significantly greater metabolism values for the normal sleepers.
It has yet to be clearly proven that sleep duration affects somatic growth. One study by Jenni et al[21] in 2007 recorded growth, height and weight, as correlated to parent-reported time-in-bed in 305 children over a period of nine years (age 1-10). It was found that "the variation of sleep duration among children does not seem to have an effect on growth". It has been shown that sleep, more specifically slow-wave sleep (SWS), does affect growth hormone levels in adult men. During eight hours sleep, Van Cauter, Leproult, and Plat[22] found that the men with a high percentage of SWS (average 24%) also had high growth hormone secretion, while subjects with a low percentage of SWS (average 9%) had low growth hormone secretion.
There are multiple arguments supporting the restorative function of sleep. We are rested after sleeping and it is natural to assume that this is a basic purpose of sleep. The metabolic phase during sleep is anabolic; anabolic hormones such as growth hormones as mentioned above are secreted preferentially during sleep. Sleep among species is, in general, inversely related to the animal size and basal metabolic rate. Rats with a very high basal metabolic rate sleep for up to 14 hours a day whereas elephants and giraffes with lower BMRs sleep only 3-4 hours per day.
Energy conservation could as well have been accomplished by resting quiescent without shutting off the organism from the environment, potentially a dangerous situation. A sedentary non-sleeping animal is more likely to survive predators, while still preserving energy. Sleep therefore does something else other than conserving energy. Most interestingly, hibernating animals that wake up from hibernation go into rebound sleep because of lack of sleep during the hibernation period. They are definitely well rested and are conserving energy during hibernation, but need sleep for something else.[23] Rats kept awake indefinitely develop skin lesions, hyperphagia, loss of body mass, hypothermia, and eventually septicemia and death.[24]
[edit] Anabolic/catabolic
Non-REM sleep may be an anabolic state marked by physiological processes of growth and rejuvenation of the organism's immune, nervous, muscular, and skeletal systems (with some exceptions). Wakefulness may perhaps be viewed as a cyclical, temporary, hyperactive catabolic state during which the organism acquires nourishment and reproduces.
[edit] Ontogenesis
According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism (Marks et al., 1995). Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass (Mirmiran et al. 1983), and an abnormal amount of neuronal cell death (Morrissey, Duntley & Anch, 2004).
REM sleep appears to be important for development of the brain. REM sleep occupies majority of time of sleep of infants, which spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses yet without any motor consequences which may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.
However, this does not explain why older adults still need REM sleep. Aquatic mammal infants do not have REM sleep in infancy [25] REM sleep in those animals increases as they age.
[edit] Memory processing
Scientists have shown numerous ways in which sleep is related to memory. In a study conducted by Turner, Drummond, Salamat, and Brown[26] working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. Turner et al. allowed 18 women and 22 men to sleep only 26 minutes per night over a 4-day period. Subjects were given initial cognitive tests while well rested and then tested again twice a day during the 4 days of sleep deprivation. On the final test the average working memory span of the sleep deprived group had dropped by 38% in comparison to the control group.
Memory also seems to be affected differently by certain stages of sleep such as REM and slow-wave sleep (SWS). In one study cited in Born, Rasch, and Gais[27] multiple groups of human subjects were used: wake control groups and sleep test groups. Sleep and wake groups were taught a task and then tested on it both on early and late nights, with the order of nights balanced across participants. When the subjects' brains were scanned during sleep, hypnograms revealed that SWS was the dominant sleep stage during the early night representing around 23% on average for sleep stage activity. The early night test group performed 16% better on the declarative memory test than the control group. During late night sleep, REM became the most active sleep stage at about 24%, and the late night test group performed 25% better on the procedural memory test than the control group. This indicates that procedural memory benefits from late REM-rich sleep whereas declarative memory benefits from early SWS-rich sleep.
Another study conducted by Datta[28] indirectly supports these results. The subjects chosen were 22 male rats. A box was constructed where a single rat could move freely from one end to the other. The bottom of the box was made of a steel grate. A light would shine in the box accompanied by a sound. After a 5 second delay an electrical shock would be applied. Once the shock commenced the rat could move to the other end of the box, ending the shock immediately. The rat could also use the 5-second delay to move to the other end of the box and avoid the shock entirely. The length of the shock never exceeded 5 seconds. This was repeated 30 times for half the rats. The other half, the control group, was placed in the same trial but the rats were shocked regardless of their reaction. After each of the training sessions the rat would be placed in a recording cage for 6 hours of polygraphic recordings. This process was repeated for 3 consecutive days. This study found that during the post-trial sleep recording session rats spent 25.47% more time in REM sleep after learning trials than after control trials. These trials support the results of the Born et al. study, indicating an obvious correlation between REM sleep and procedural knowledge.
Another interesting observation of the Datta study is that the learning group spent 180% more time in SWS than did the control group during the post-trial sleep-recording session. This phenomenon is supported by a study performed by Kudrimoti, Barnes, and McNaughton.[29] This study shows that after spatial exploration activity, patterns of hippocampal place cells are reactivated during SWS following the experiment. In a study by Kudrimoti et al. seven rats were run through a linear track using rewards on either end. The rats would then be placed in the track for 30 minutes to allow them to adjust (PRE), then they ran the track with reward based training for 30 minutes (RUN), and then they were allowed to rest for 30 minutes. During each of these three periods EEG data were collected for information on the rats’ sleep stages. Kudrimoti et al. computed the mean firing rates of hippocampal place cells during pre-behavior SWS (PRE) and three 10-minute intervals in post-behavior SWS (POST) by averaging across 22 track-running sessions from seven rats. The results showed that 10 minutes after the trial RUN session there was a 12% increase in the mean firing rate of hippocampal place cells from the PRE level, however after 20 minutes the mean firing rate returned rapidly toward the PRE level. The elevated firing of hippocampal place cells during SWS after spatial exploration could explain why there were elevated levels of SWS sleep in Datta’s study as it also dealt with a form of spatial exploration.
The different studies all suggest that there is a correlation between sleep and the many complex functions of memory. Harvard sleep researchers Saper and Stickgold[30] point out that an essential part of memory and learning consists of nerve cell dendrites sending information to the cell body to be organized into new neuronal connections. This process demands that no external information is presented to these dendrites, and they suggest that this may be why it is during sleep that we solidify memories and organize knowledge.
Further information: Sleep and learning, Sleep and creativity
[edit] Preservation
The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the person during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats. (Allison & Cicchetti, 1976; Webb, 1982).
However, this theory fails to explain why the brain disengages from the external environment during normal sleep. Another argument against the theory is that sleep is not simply a passive consequence of removing the animal from the environment, but is a "drive": animals alter their behaviors in order to obtain sleep. Therefore, circadian regulation is more than sufficient to explain periods of activity and quiescence that are adaptive to an organism, but the more peculiar specializations of sleep probably serve different and unknown functions.
Moreover, the preservation theory does not explain why carnivores like lions, which are on top of the food chain, sleep the most. By the preservation logic, these top carnivores should not need any sleep at all. Preservation does not explain why aquatic mammals sleep while moving. Lethargy during these vulnerable hours would do the same, and will be more advantageous because the animal will be quiescent but still be able to respond to environmental challenges like predators etc. Sleep rebound that occurs after a sleepless night will be maladaptive, but still occurs for a reason. For example, a zebra falling asleep the day after it spent the sleeping time running from a lion is more and not less vulnerable to predation.
[edit] Dreaming
Main article: Dream
Dreaming is the perception of sensory images and sounds during sleep, in a sequence which the sleeper/dreamer usually perceives more as an apparent participant than an observer. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep.
People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconscious, and he used dream interpretation in the form of psychoanalysis to uncover these desires. Scientists have become skeptical about the Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. See Freud: The Interpretation of Dreams
Rosalind Cartwright stated that
One Function of dreams may be to restore our sense of competence.... it is also probable that in many times of stress, dreams have more work to do in resolving our problems and are thus more salient and memorable.[31]
– Rosalind Cartwright, The Sunday Observer
J. Allan Hobson's and Robert McCarley's activation synthesis theory proposes that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period. According to the theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it; hence the odd nature of many dreams.[32]
[edit] Effect of food and drink on sleep
[edit] Depressants
Tryptophan
The amino acid tryptophan is a building block of the protein found in foods. It contributes to sleepiness. Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals containing tryptophan tend to cause drowsiness. Tryptophan is a precursor to the neurotransmitter serotonin, which is a precursor to the neurohormone melatonin (see below).
Melatonin
Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. Melatonin supplementation may be used as a sleep aid, both as a hypnotic and as a chronobiotic (see phase response curve, PRC).
5-hydroxy-tryptophan (5-HTP)
5-HTP, the precursor to serotonin (5-HT) can cause drowsiness when ingested.
The "Post-Lunch Dip"
Many people have a temporary drop in alertness in early afternoon, commonly known as the post-lunch dip. While a large meal, rich in carbohydrates, can make a person feel sleepy, the post-lunch dip is mostly an effect of the biological clock. People naturally feel most sleepy (have the greatest "drive for sleep") at two times of the day about 12 hours apart, for example at 2:00 AM and 2:00 PM. At those two times, the body clock "kicks in". At about 2 p.m. (14:00), it overrides the homeostatic build-up of sleep debt, allowing several more hours of wakefulness. At about 2 a.m. (02:00), with the daily sleep debt paid off, it "kicks in" again to ensure a few more hours of sleep.
Alcohol
Often people start drinking alcohol in order to get to sleep (alcohol is initially a sedative and will make you get to sleep faster). However, being addicted to alcohol can lead to disrupted sleep because alcohol has a rebound effect later in the night. As a result there is strong evidence linking alcoholism and insomnia.[citation needed]
Barbiturates
Barbiturates when taken cause drowsiness and have actions similar to ethanol (drinking alcohol).
[edit] Stimulants
Caffeine
Caffeine is a stimulant that works by slowing the action of the hormones in the brain that cause sleepiness. Effective dosage is individual, in part dependent on prior usage. It can cause a rapid reduction in alertness as it wears off.
Energy Drinks
The stimulating effects of energy drinks comes from natural stimulants such as caffeine, sugars, and essential amino acids, and eventually will create a rapid reduction in alertness similar to that of caffeine.
Amphetamines
Amphetamines (amphetamine, dextroamphetamine, methamphetamine, etc) are often used to treat narcolepsy and ADHD disorders, the most common effects are decreased appetite, stimulation and insomnia, and increased alertness.
Cocaine and Crack Cocaine
Similar in action to the amphetamines.
MDMA
Commonly known as ecstacy, users are kept awake similar to amphetamines with intense euphoria, includes other similar drugs like MDA, MMDA, or bk-MDMA.
Methylphenidate
Commonly known as Ritalin, similar in action to amphetamines and cocaine.
[edit] Causes of difficulty in sleeping
There are a great many possible reasons for sleeping poorly. Following sleep hygienic principles may solve problems of physical or emotional discomfort.[33] When pain, illness, drugs or stress are the culprit, the cause must be treated. Sleep disorders, including the sleep apneas, narcolepsy, primary insomnia, periodic limb movement disorder (PLMD), restless leg syndrome (RLS) and the circadian rhythm sleep disorders, are treatable.
Elderly people may to some degree lose the ability to consolidate sleep. They need the same amount per day as they've always needed, but may need to take some of their sleep as daytime naps.
[edit] Anthropology of sleep
Recent research suggests that sleep patterns vary significantly across human cultures.[34][35] The most striking differences are between societies that have plentiful artificial light and ones that do not. Cultures without artificial light have more broken-up sleep patterns. This is called polyphasic sleep or segmented sleep and has led to expressions such as "first sleep," "watch," and "second sleep" which appear in literature from all over the world.
Some cultures have fragmented sleep patterns in which people sleep at all times of the day, and for shorter periods at night. For example, many Mediterranean and Latin American cultures have a siesta, in which people sleep for a period in the afternoon. In many nomadic or hunter-gatherer societies people sleep off and on throughout the day or night depending on what is happening.[citation needed]
[edit] Sleep in non-humans
Sleeping Japanese Macaques.
Main article: Sleep (non-human)
Horses and other herbivorous ungulates can sleep while standing, but must necessarily lie down for REM sleep (which causes muscular atony) for short periods - giraffes, for example, only need to lie down for REM sleep for a few minutes at a time. Bats sleep while hanging upside down. Some aquatic mammals and some birds can sleep with one half of the brain, while the other half is awake, so called unihemispheric slow-wave sleep.[36] Birds and mammals have cycles of non-REM and REM sleep as described above for humans, though birds’ cycles are much shorter and they do not lose muscle tone (go limp) to the same extent that most mammals do.
Many animals sleep, but neurological sleep states are difficult to define in lower order animals. In these animals, sleep is defined using behavioral characteristics such as minimal movement, postures typical for the species and reduced responsiveness to external stimulation. Sleep is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer and/or deeper sleep. Herbivores, who require a long waking period to gather and consume their diet, typically sleep less each day than similarly sized carnivores who might well consume several days supply of meat in a setting.
Many species of mammals sleep for a large proportion of each 24-hour period when they are very young.[37] However, killer whales and some dolphins do not sleep during the first month of life.[38] Such differences may be explained by the ability of land mammal newborns to be easily protected by parents while sleeping, while marine animals must, even while very young, be more continuously vigilant for predators.
William C Dement in his book "The Promise of Sleep". states that the dolphin, originally a land mammal that has returned to the sea, maintains a numer of terrestrial traits including bearing their offspring alive and, unlike fish, breathing air. When terrestrial mammals breathe, they do so through an involuntary process similar to the one that causes our hearts to beat continuously. In dolphins the breathing process is under voluntary control throughout the day --- a process that, seemingly, would preclude sleep. In order to accomplish what seems to be an impossible task, dolphins allow one half of their brain to go to sleep while the other half remains awake. This is accomplished in two-hour cycles where one half of the brain is awake while the other half sleeps until the dolphin's day's sleep need has been fulfilled
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