Flashcards in A2 Biopsychology - Endogenous Pacemakers and Exogenous Zeitgebers Deck (4)
Describe an endogenous pacemaker.
An internal pacemaker that regulates the s/w cycle. In humans, this is the suprachiasmatic nucleus (SCN); a bundle of nerve cells in the hypothalamus.
SCN receives information on light from the optic chasm (which sits just below the SCN) and sends information to the pineal gland which produces melatonin to make us sleepy. This occurs even when our eyes are shut and not receiving light.
Evaluate endogenous pacemakers.
DeCoursey et al (2000) destroyed the SCN of 30 chipmunks and found that their s/w cycle disappeared. Most were killed by predators as a result. This shows that the SCN is crucial in keeping the s/w cycle as the chipmunks were awake when they should've been asleep.
(-) ethical issues as most of the chipmunks were killed
(-) problems generalising to humans.
(+) application to chronotherapeutics as the SCN keeps our s/w cycle steady
Describe exogenous zeitgebers
Light is an external factor which can reset the SCN through the process of entrainment and keeps the s/w cycle at 24 hrs and not 25. Regular mealtimes and other daily routines also help to keep the s/w cycle at 24hrs and not the natural 25.