Biological rhythms: Circadian rhythms

Question 1

A01

Biological rhythms

Answer 1

Distinct patterns of changes in body activity that conform to cyclical time periods, Biological rhythms are influenced by internal body clock ( endogenous pacemakers)
& external changes in enviroment ( exogenous zeitgebers)

Question 2

A01

Circadian rhythms

Answer 2

Biological rhythm that operates on a 24 hour cycle which regulates number of body processes such as sleep wake cycle and changes in core body temperature, sleeping & feeding patterns , alertness

Question 3

A01

Ao1 outline biological rhythms

Answer 3

Biological rhythms are governed by 2 things
bodys internal biological clock -endogenous pacekmakers
external changes in the enviroment -exogenous zeitgebers
circadian rhythms are rhythms that operate on a 24 hour cycle
2 examples of circadian rhythm are sleep/wake cycle & core body temperature

Question 4

A01

Outline sleep wake cycle-circadian rhythm

Answer 4

sleep wake cycle is e.g of circadian rhythm
humans & animals sleep or wake up according to this cycle , depending on amount of light (exogenous zeitgeber) they exposed to

sleep wake cycle is also governed by internal biological clocks - like suprachiasmatic nucleus (SCN) ( endogenous pacemaker)
The SCN lies above the optic chiasm which recieves info from eye about light
when light is detected by the SCN it sends light to pineal gland stopping production of melatonin , a hormone that results in sleep response
* exogenous zeitgebers light can reset SCN
* light is primary exogenous zeitgeber in sleep wake cycle
* social cues like when we time meals, exercise or enviromental cues like clocks also act as EZ
* shift work has been found to lead to desynchronization of circadian rhythms & can lead to adverse cognitive & psychological effects
e.g memory lapses or issues with fertility
jet lag is also e.g that can lead to desynchronisation of circadian rhythms

Question 5

A01

research support Aschoff & weaver

Answer 5

convinced a group of p to spend 4 weeks in a world war 2 bunker deprived of natural light , all but one of the p ( whose sleep cycle extended to 29 hours) displayed a circadian rhythm between 24 & 25 hours
both siffres experiences & bunker study suggest that natural sleep wake cycle may be longer than 24 hours

Question 6

A01

supporting research for circadian rhythms-Siffres cave study

Answer 6

Siffre is a self styled cave man who spent several extended period underground to study effects of his own biological rhythm ,spent 6 months in a cave deprived of natural light , sound , other exogenous zeitgebers like clocks or social cues -siffres body clock maintained a regular cycle of around 25 hours without EZ, longer than expected 24 hour cycle , suggesting that EP for sleep wake cycle is free running but needs entrainment to keep 24 hour day night cycle

Environmental factors have an influence on biological rhythms through a process known as ‘entrainment’.

Question 7

A03

Individual differences between -Cziesler-sleep wake cycle vary 13-65 hours
duffy-preferences, difficult to generalise

Limitation

Answer 7

Limitation of research into circadian rhythms is that generalisations are difficult to make studies like Siffre are based on small samples of p
it seems that sleep wake cycle may vary from person to person
Czeisler found individual differences in sleep wake cycle varying from 13 to 65 hours
duffy et al revealed that some people have natural preference for going to bed early and rising early whereas others have prefer the oppositite
thus difficult to generalise findings

Question 8

A03

circadian rhythms used in medical treatment

strength

Answer 8

Circadian rhythms improved medical treatments
circadian rhythms co-ordinate number of basic processes such as heart rate, digestion , hormone levels
these rise and fall during the course of a day which has led to the field of chronotherapeutics- how medical treatments can be administrated in a way that corresponds to a persons biological rhythm. e.g aspirin as a treatment for heart attacks is most effective if taken at night
thus circiadian rhythm research can help increase effectiveness of drug treatment

Question 9

A03

poor control in studies-csiezler

Limitation

Answer 9

Although p in studies deprived of natural light , they still had access to artificial light, e.g siffre turned on a lamp everytime he woke up which remained on until he went to bed, it was assumed by him that artificial light, unlike natural light would have no effect on free run biological rhythm , but czeisler et al were able to adjust p circadian rhythms from 22 to 28 hours using dim light