endogenous pacemakers

Question 1

what is an endogenous pacemaker?

Answer 1

internal body clock that regulates many biological rhythms such as the influence of the SCN on the sleep wake cycle

Question 2

what is the SCN? what are its roles?

Answer 2

the suprachiasmatic nucleus is a tiny bundle of nerve cells located in the hypothalamus of each hemisphere . It is influential in maintaining circadian rhythms. It receives info about light from the optic chiasm and this continues even when our eyes are shut so our biological clock can adjust to changing patterns of daylight when we sleep

Question 3

how are animals used to study the SCN?

Answer 3

SCN connections were destroyed in 30 chipmunks ad they returned to their natural habitat to be observed for 80 days. The sleep wake cycle disappeared and by the end of the study a number of them had been killed by predators (presumably as they were awake and vulnerable instead of being asleep). In another study, mutant hamsters were bred with a 20 hour s/w cycle. when tissue from their SCN was transplanted into normal hamsters, the cycles of the second group changed to 20 hours.

Question 4

explain the role of the pineal gland

Answer 4

the info from the SCN about light is passed on the the pineal gland. This is another endogenous mechanism that guides the s/w cycle. During the night, the pineal gland increases production of melatonin (sleep-inducing chemical)

Question 5

what is a limitation of endogenous pacemakers? (SCN research)

Answer 5

SCN research may obscure other biological clocks. Research has revealed there are other circadian rhythms in many organs and cells. They are influenced by the SCN, but can act independently. For example, a change in feeding patterns can affect certain cells but there’s no affect on the SCN. This suggests there are other complex influences on the SW cycle

Question 6

what is a limitation of endogenous pacemakers? (isolation)

Answer 6

they can’t be studied in isolation. Total isolation studies such as Siffre are extremely rare. Also siffre used artificial light which may have reset his biological clock every time he turned it on. In everyday life, EPs and EZs interact so it makes little sense to separate the 2 for research purposes. this suggests the more researchers attempt to isolate EPs, the lower the validity of the research