Endogeouns pacemakers and Exogenous zeitgebers

Question 1

What is the suprachaismatic nucleus

Answer 1

endogenous pacemaker
- bundle of nerve cells in the hypothalamus it maintains circadian rhythms

Question 2

How does the SCN maintain biological rhythms

Answer 2

-nerve fibres are connected to eye so the SCN receives information about light even when our eyes are closed

• this allows the biological clock to adjust to changing patterns in day light whilst were asleep

Question 3

Outline Decoursey et als study into SCN

Answer 3

• destroyed SCN connections in the brain of 30 chipmunks snd they were returned to their natural environment and observed for 80 days
• observations showed that the sleep wake cycle if the chipmunks had disappeared
• by the end of the study a significant amount of chipmunks were killed by predators

Question 4

Evaluate ethical issues as a limitation of DeCoursey et als stufy

Answer 4

• unethical
• its evident that chipmunks were exposed to a considerable risk and harm when they were returned to their natural habitat
• matter of debate whether significance of their findings is of sufficient value to justify the aversive procedures they employed

Question 5

Outline morgan et als study into the SCN

Answer 5

• bred a strain of hamsters so they had abnormal circadian rhythms of 20 hrs
• SCN neurones of the abnormal hamsters were transplanted into the brains of normal hamsters
• normal hamsters they displayed the same 20 hrs circadian rhythm showing that the transplanted SCN had imposed its patters into recipients

Question 6

Evaluate extrapolation as a limitation of Morgan et als study

Answer 6

• study was done in animals so theres issues associated with extrapolation of findings to humans
• its not certain that transplanting SCN neurons i to human brains would have the same effect since human brains are much more sophisticated
• so any conclusions drawn in relation to endogenous pacemakers should be treated with caution
• however even though hamsters are less sophisticated they are sufficiently similar to argue to argue then the SCN also plays a significant role in maintaining circadian rhythms

Question 7

What is the pinealgland?

Answer 7

an endogenous pacemaker in the pineal gland
- The pineal gland receives info about day length and night from the SCN
- during the night it increases the production of melatonin

Question 8

What is melatonin?

Answer 8

a chemical which induces sleep
- production of melatonin is inhibited during the day

Question 9

What is a limitation of endogenous pace makers

Answer 9

they are hard to study

Question 10

Evaluate hard to study as a limitation of endogenous pacemakers

Answer 10

• impossible to study in isolation from other factors which may affect the sleep/wake cycle
• even siffre used an artificial light in his cave study which may have reset his biological clock
• this means its difficult to prove the significance of the role played by endogenous pacemakers in the sleep/wake cycle particularly since in real life endogenous and exogenous interact

Question 11

How does light effect the sleep wake cycle?

Answer 11

it’s an exogenous zeitgeber that can reset the body’s main endogenous pacemaker thus playing a role in the maintenance
of the sleep/wake cycle
- light also has a main indirect influence on key processes in the body that control functions such as hormone secretion

Question 12

How do social cues affect the sleep wake cycle in babies

Answer 12

• The sleep/wake cycle of new-borns is random but at 6 weeks of age the circadian rhythm begins and at 16 weeks they have been entrained by schedules imposed by their parents
• this is by social cues such as mealtimes and bedtimes

Question 13

How do social cues affect the sleep wake cycle when travelling?

Answer 13

• research on jet lag suggests that adopting local times for eating and sleeping immediately on arrival rather than maintaining ones followed at home is an effective wat pf entraining circadian rhythms

Question 14

What is entrainment

Answer 14

an individual chronobiological, physical and behavioural relationship with their environment
- an individual physical and mental adaption to the time zone which they live in

Question 15

What are limitations of exogenous zeitgebers?

Answer 15

• dont have the same effect in all environments
• exaggerated

Question 16

Evaluate inconsistency as a limitation of exogenous zeitgebers

Answer 16

• they don’t have the same effect in all environments
• for example a researcher spent six months in total darkness but had the same sleep/wake cycle all year long
• this suggests that endogenous pacemakers are far more important in regulating the sleep/wale cycle than exogenous zeitgebers

Question 17

Evaluate exaggeration as a limitation of exogenous zeitgebers

Answer 17

• number of case studies have suggested that the effext of exogenous zeitgebers on sleep/wake cycle has been exaggerated
• a case study found that a young blind man from birth has an abnormal circadian rhythm of 24.9 hours despite exposure to social cues such as regular mealtimes
• suggests that social cues are insufficient to determine the sleep/wake cycle and that other factors must be involved

Question 18

Evaluate biological reductionism as a limitation of endogeous pacemakers and exogenous zeitgebers

Answer 18

• considered biologically reductionist
• It’s suggested that other people and social norms influence bodily rhythms, hence why we typically sleep when it’s dark. However, it would be impossible to conduct normal routines during the night
• Consequently this research can be criticised for being biologically reductionist as it emphasises the role of biological mechanisms and fails to consider alternative influences
• this would suggest that the sleep-wake cycle could be better explained as resulting from an interaction between biological and social factors together