endogenous pacemakers and exogenous zeitgebers

Question 1

what is the SCN?

Answer 1

the suprachiasmatic nucleus

Question 2

where is the SCN?

Answer 2

a small bundle of nerves located in the hypothalamus in each hemisphere just above the optic chiasm so can receive information directly from it, so we can adjust eve when asleep

Question 3

why is the SCN important?

Answer 3

one of the primary endogenous pacemakers in mammalian species and influential in maintaining the sleep/wake cycle

Question 4

describe Decoursey et al’s study

Answer 4

destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat an observed for 30 days

Question 5

what are the findings of Decoursey et al’s study?

Answer 5

the sleep/wake cycle in the chipmunks disappeared cusing a significant proportion to be killed by preditors

Question 6

describe Ralph et al’s study

Answer 6

bred mutant hamsters with 20-hour sleep/wake cycles the transplanted the scn cells from fetal tissue of the mutant hampsters into normal hamsters

Question 7

what are the findings of Ralph et al’s study?

Answer 7

the hamsters deflected to a 20-hour cycle emphasising the role of the SCN in establishing and maintaining the sleep/wake cycle

Question 8

where does the SCN pass information to?

Answer 8

the pineal gland which produces melatonin at night

Question 9

what does light reset?

Answer 9

the body’s SCN

Question 10

what des light indirectly influence?

Answer 10

hormone secretion and circulation in the blood

Question 11

describe Campbell and Murphy’s study

Answer 11

15 ppt woken at various times in the night had a light pad shone on the back of their knees but not to their eyes

Question 12

what did Campbell and Murphy aim to demonstrate?

Answer 12

that light may be detected by skin receptor sites on the body even when the same information is not given to the eyes

Question 13

what were the results of Campbell and Murphy’s study?

Answer 13

the sleep cycle deviated by up to 33 hours

Question 14

when approximately do circadian cycles begin?

Answer 14

6 weeks of age

Question 15

whe re most babies entrained?

Answer 15

16 weeks likely influenced by their parents imposed schedules (meal and bedtimes)

Question 16

what is the application of understanding social cues and exogenous zeitgebers?

Answer 16

adapting to local time zones by adapting to their sleeping and eating times

Question 17

what are peripheral oscillators?

Answer 17

the many organs and cells that have their own independent circadian rhythms but are also healivy influenced by the SCN

Question 18

where are Peripheral oscillators found?

Answer 18

the adrenal glands, oesophagus, lungs, liver, pancreas, spleen, skin, thymus

Question 19

Describe Damiola et al’s study and results?

Answer 19

demonstrate how changing feeding patterns in mice can alter the circadian rhythms of cells in the liver by up to 12 hours while not effecting the SCN

Question 20

what are the ethical problems of the animal studies?

Answer 20

animals exposed to the risk of significant harm when released back into their natural habitat and somewhere killed

Question 21

describe the case study of Miles et al and how it is applied

Answer 21

a young man blind from birth had a circadian rhythm of 24.9 hours and despite exposure to social cues it could not be adjusted and he had to be sedated at night and stimulated in the mornings to ft into a 24-hour world. this means the influence of exogenous zeitgebers may be overestimated

Question 22

give a real-world example which demonstrates the influence of exogenous zeitgebers may be overestimated

Answer 22

people who live in the arctic regions show normal sleep patterns despite prolonged periods of exposure to light

Question 23

what are the methodological issues with Campbell and Murphy’s study?

Answer 23

• hasn’t been replicated

- confounding variables (light reaching eyes)

Question 24

what are the practical applications of the effect of exogenous zeitgebers on the sleep/wake cycle and studies into the SCN?

Answer 24

• treating sleep disorders

- understanding the effect of a damaged SCN

Question 25

what is an interactionist system?

Answer 25

in real-life pacemakers, and zeitgebers interact so it doesn’t make sense to separate them