Endogenous Pacemakers And Exogenous Zeitgebers Flashcards
Outline- SCN
- stands the the suprachiasmatic nucleus
- it’s a tiny Bundle of nerve cells located in the hypothalamus in each hemisphere.
- it’s our primary endogenous pacemaker and is responsible for maintaining circadian rhythms such as the sleep/wake cycle
Outline- animal studies and the SCN
-DeCoursey et al (2000)
- destroyed SCN connections in 30 chipmunks
- they were returned to their natural habitat for 80 days while being observed.
Found- their sleep wake cycle disappeared and by the end most had been killed by preditors as a result.
Outline- the pineal gland and melotonin
-during the night the SCN passes that info to the pineal gland to make it release melatonin (a sleep inducing chemical that’s inhibited during wakefulness)
Outline- exogenous zeitgebers
- external factors in the environment that reset our biological clocks.
- in the absence of external cues, we can still maintain a sleep/wake cycle suggesting we rely on both endogenous pacemakers and exogenous zeitgebers
Outline- light
-light is an exogenous zeitgeber
Campbell and Murphy (1998)
- shone light on the back of participants knees In the middle of their sleep and it woke them up
-suggests that light can be detected by skin receptors when our eyes can’t see it.
Outline- social cues
-the fact that we go to sleep when we are told or when everyone else does is a social cue that acts as an exogenous zeitgeber.
Evaluation- Damiola et al limitation
- changed feeding pattern in mice can affect the circadian rhythm of cells in the liver by up to 12 hours.
- this suggests there may be other complex influences on the sleep/wake cycle aside from the SCN
Evaluation- miles
- case study on a blind man from birth
- he had a circadian rhythm of 24.9 hours
- despite social cues his cycle couldn’t be adjusted and therefore had to take sedatives to sleep.
- suggests the effects of social cues are overstated
