Endogenous Pacemakers And Exogenous Zeitgebers

Question 1

Endogenous pacemaker

Answer 1

Internal body clock that regulate many of our biological rhythms, such as the influence of the SCN on the sleep/wake cycle

Question 2

Exogenous pacemakers

Answer 2

External factors that affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle

Question 3

Exogenous zeitgebers

Answer 3

‘Time-givers’ entrain free-running endogenous rhythms

Question 4

The SCN

Answer 4

SCN receives info about light from optic chiasm

Question 5

Animal studies and the SCN
(DeCoursey)

Answer 5

Sleep/Wake cycle disappeared when the SCN destroyed (DeCoursey)

Question 6

Animal studies and the SCN
(Ralph)

Answer 6

SCN transplanted from mutant hamsters with 20 hour sleep cycle (Ralph)

Question 7

The pineal gland and melatonin

Answer 7

The SCN passes info to the pineal gland that controls melatonin

Question 8

Light research (Campbell and Murphy)

Answer 8

Light shin on back of knees change rhythm by up to 3 hours
(Campbell and Murphy)

Question 9

Social cues related to babies sleep rhythms

Answer 9

Babies rhythms and jet lag are entrained by bedtimes and mealtimes

Question 10

Endogenous pacemakers evaluation points- Beyond the master clock

Answer 10

LIMITATION

Other body clocks (peripheral oscillators) E.g circadian rhythm of liver cells in mice altered but SCN unaffected (Damiola) 

Question 11

Endogenous pacemakers evaluation points- Interactionist system

Answer 11

LIMITATION

Research looks at pacemakers zeitgebers in isolation, approach lacks validity.

Question 12

Exogenous Zeitgebers evaluation points- Environmental observations

Answer 12

LIMITATION

EZs do not have same effect on people who live in darkness in summer and little light in winter

Question 13

Exogenous Zeitgebers evaluation points- Case study evidence

Answer 13

LIMITATION

Man blind from birth with sleep/wake cycle of 24.9 hours, could not adjust despite social cues E.g . Mealtimes (Miles)