endogenous pacemakers and exogenous zeitgebers

Question 1

what are endogenous pacemakers

Answer 1

internal body clocks that regulate many of our biological rhythms
- such as the SCN in the sleep/wake cycle

Question 2

the suprachiasmatic nucleus (SCN)

Answer 2

a tiny bundle of never cells in the hypothalamus in each hemisphere
- influential in maintaining circadian rhythms like the sleep/wake cycle
- receives info ab light from the optic chiasm

Question 3

animal studies and SCN

Answer 3

1. DeCoursey et al - chipmunks
2. Ralph et al - mutant hamsters
   - both emphasise the role of the SCN in establishing and maintaining the circadian sleep/wake cycle

Question 4

DeCoursey et al

Answer 4

destroyed SCN connection in 30 chipmunks
- returned to natural habitat for 80 days
- found sleep/wake cycle had disappeared
- many had been killed by predators bc they were awake and vulnerable when they should have been asleep

Question 5

Ralph et al

Answer 5

bred mutant hamsters w 20 hour sleep/wake cycle
- SCN cells from foetal tissue of mutants placed into brains of group of normals
- cycles of this group defaulted to 20 hours

Question 6

the pineal gland

Answer 6

receives info ab day length and light from the SCN
- increases melatonin production at night

Question 7

melatonin

Answer 7

a chemical that induces sleep and if inhibited during period of wakefulness
- suggested as a causal factor in SAD

Question 8

exogenous zeitgebers

Answer 8

external cues that may affect or entrain our biological rhythms
- eg. influence of light on sleep/wake cycle

Question 9

examples of exogenous zeitgebers

Answer 9

1. light
2. social cues

Question 10

light as an exogenous zeitgeber

Answer 10

can reset the body’s main endogenous pacemaker (SCN) so plays a role in SWC
- also indirect influence on key processes that control functions like hormone secretion and blood circulation

Question 11

light exogenous study

Answer 11

Campbell and Murphy

Question 12

Campbell and Murphy

Answer 12

found light can be detected by skin receptor sites
- 15 ppts woken at diff times and a light pad was shone on the back of their knees
- managed to deviate usual SWC by up to 3 hours

CA - yet to be replicated so may lack reliability

Question 13

social cues as an exogenous zeitgeber

Answer 13

seen in infants mainly
- initial SWC is random
- at 6weeks, circadian develops and by 16 weeks, most are entrained
- schedule imposed by parents is a key influence (nap and meal times)

Question 14

entraining circadian rhythms

Answer 14

research suggests adapting to local times for eating and sleeping is an effective way of entraining and beating jet lag when travelling
- eat at local times instead of own feelings of hunger and fatigue before a trip

Question 15

supporting evaluation

Answer 15

1. Siffre
2. Czeisler

Question 16

Czeisler

Answer 16

studied effects of light and dark on circadian rhythm
- control group worked in dim light during night shift
- experimental had bright lights during night shift
- experimental circadian shifted by 9 hours, control stayed the same
- improvement in alertness

Question 17

opposing evaluation

Answer 17

1. animal studies
   - hard to extrapolate and generalise
   - also unethical, animals exposed to harm and risk when returned to their habitats