ENDOGENOUS PACEMAKERS AND EXOGENOUS ZEITGEBERS

Question 1

what 3 things must we remember for endogenous pacemakers and sleep/wake cycle?

Answer 1

SCN
animal studies and SCN
pineal gland and melatonin

Question 2

what is the SCN?

Answer 2

suprachiasmatic nucleus, tiny bundle of cells located in the hypothalamus in each hemisphere of brain

Question 3

it is one of the….. in mammalian species and is influential in ….

Answer 3

one of primary endogenous pacemakers and is influential in maintaining circadian rhythms

Question 4

what do nerve fibres connected to eye cross over?

Answer 4

cross in area called optic chiasm on way to visual area of cerebral cortex

Question 5

where does the SCN lie?

Answer 5

above the optic chiasm

Question 6

what does the SCN recieve info abt?

Answer 6

abt light directly from the optic chiasm

Question 7

when does the SCN recieve info abt light?

Answer 7

when we have our eyes open and closed, enabling biological clock to adjust to changing patterns of daylight whilst we are asleep

Question 8

who conducted animal research into SCN?

Answer 8

DeCoursey et al

Ralph et al

Question 9

what did DeCoursey et al do?

Answer 9

destroyed SCN connections in brains of 30 chipmunks, returned to habitat and observed for 80 days

Question 10

what happened to the sleep/wake cycle of chipmunks in DeCoursey et al’s study?

Answer 10

disappeared, end of the study significant proportion of them killed by predators

Question 11

what happened in the study of Ralph et al?

Answer 11

bred ‘mutant’ hamsters with 20hr wake and sleep cycle

Question 12

what happened to the hamsters in Ralph et al?

Answer 12

SCN cells from foetal tissue of mutant hamsters transplanted brains of normal hamsters

Question 13

the cycles of the second groups hamsters….

Answer 13

defaulted to 20 hours

Question 14

when is the pineal gland active?

Answer 14

during the night

Question 15

what does the pineal gland increase production of?

Answer 15

melatonin

Question 16

define melatonin

Answer 16

a chemical that induces sleep and is inhibited during periods of wakefulness

Question 17

what had melatonin been suggested as a factor in?

Answer 17

a factor in seasonal affective disorder

Question 18

what are exogenous zeitgebers?

Answer 18

external factors in the environment that reset our biological clocks through entrainment

Question 19

what happens in the absence of external cues?

Answer 19

free running biological clock controls sleep/wake cycle e.g Siffre

Question 20

what is the key exogenous zietgeber?

Answer 20

light

Question 21

what does light reset?

Answer 21

the body’s main endogenous pacemaker

Question 22

what does light have an indirect influence on?

Answer 22

key processes in the body that control functions such as functions like hormone secretion and blood circulation

Question 23

who studied light?

Answer 23

Campbell and Murphy

Question 24

what did Campbell and Murphy demonstrate?

Answer 24

light may be detected by skin receptor sites even when info is not at eyes

Question 25

what did Campbell and Murphy do?

Answer 25

woke up 15 ppts at various times and light shone onto back of legs, produced deviation is sleep/wake cycle

Question 26

what does Campbell and Murphy's study suggest?

Answer 26

light is a powerful exogenous zeitgeber, don't need to rely on eyes

Question 27

what is another exogenous zeitgeber apart from light?

Answer 27

social cues

Question 28

at 6 weeks of age, what begins?

Answer 28

circadian rhythms and by 16 weeks babies are entrained

Question 29

how are babies entrained into circadian rhythms?

Answer 29

schedules imposed by parents such as mealtimes and bedtimes

Question 30

what does research suggest about social cues?

Answer 30

adapting to local times for eating and sleeping, is an effective way of entraining circadian rhythms and beating jet lag