endogenous pacemakers + exogenous zeitgebers✅

Question 1

ENDO:

what is an endogenous pacemaker?

what does SCN mean? what is it

where is the SCN located?

Answer 1

• internal body clocks that regulate any of a biological rhythms such as the influence of the SCN on the sleep wake cycle
• the suprachiasmatic nucleus - bundle of nerve cells In the hypothalamus in each hem. of the brain
• just above the optic chiasm, receives info about light directly from this structure. this continues even when our eyes are closed, enabling the body clock to adjust to changing patterns of daylight when were asleep

Question 2

ENDO:

how did DeCoursey use animal studies to study the influence of the SCN?

what happened to their sleep wake cycle?

Answer 2

• they destroyed the SCN connection in the brains of 30 chipmunks who then returned to their natural habitat and were observed for 80 days
• it had disappeared and by the end of the study a lot of them had been killed by predators, prob bc they were awake at vulnerable times when they should have been sleep

Question 3

ENDO:
the pineal gland and melatonin:

what info does the SCN pass to the PG?

what does the PG do in the night?

Answer 3

• info on day length and light that it receives

- increases the product of melatonin … a chemical that induces sleep

Question 4

EXO:

what is an exogenous zeitgeber?

Answer 4

• external factors that may affect our biological rhythms such as the influence of light of the sleep wake cycle

Question 5

EXO;
LIGHT

what does light have an indirect influence on?

who studied this? what did they look at?

what did they do?

what does this suggest?

Answer 5

• key processes in the body that control such functions as hormone secretion and blood circulation
• Murphy and campbell … looked at how light may be detected by skin receptor sites on the body even when the same info is not received by the eyes
• 15 ppts were waken at different times in the night and a light pad was shone on the back of their knees. found a deviation in their usual sleep wake cycle of up to 3 hrs.
• suggests light is a powerful EZ that doesn’t need to rely on the eyes only for it to be sent to the brain

Question 6

EXO:
SOCIAL CUES:

what is the sleep wake cycle like in babies?

what is the key social cue In babies?

what does research suggest?

Answer 6

• random at first, at about 6 weeks old circadian rhymes become entrained
• parents schedules such as mealtimes and bedtime
• adapting to local times for eating and sleeping rather then when your body wants, is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances

Question 7

AO3

✅ strength

❌ weakness

Answer 7

✅ research to support the role of EZ. when sifre returned from under ground
with no clocks or light, he believed the date to be a month earlier then it was. this suggests his 24 hr sleep wake cycle was increased due to a lack of extra cues, making him believe the day was longer than it was - highlighting the impact of bodily clocks

❌ studied on animals are flawed due to a lack of generalisabity. when Morgan used hamsters and looked at their SCN’s, they are going to respond differently to humans. not only because were different biologically, also the vast difference between environmental contexts. this makes research carried out on animals unable to explain the impacts of EP’s on humans