What are the definitions of-
Circadian Rhythms- Cycle length of 24hrs eg. Sleep/wake cycle.
Ultradian Rhythms- Rhythm lasting less than a day eg sleep- cycle.
Infradian Rhythms- Longer than a day eg. Menstrual Cycle.
What controls Circadian Rhythms? – Endogenous pacemakers (internal) eg hormones, suprachiasmatic nucleus (BioClock). Also Exogenous zeitgebers (external) eg. Light/dark, clocks.
What is the research evidence supporting endogenous control (internal) of Circadian Rhythms?- Siffre-Cave Study- Aim- To determine what causes rhythm of life when external factors are removed. Siffre was wired up to monitor the heart, muscle and brain. In constant temperature, had artificial light he could have off/on. Tests everyday (blood pressure, exercise etc). Researchers in 24hr phone contact (business like convos). Shortest cycle=16hrs, Longest=51hrs but average day 25hrs- suggest body clock is indogenous. However, Siffre still suffers memory lapses & has weakened eyesight. Morgan- Hamster study- Removed SCN & their circadian rhythm disappeared. Schochat-Sleep Gate study- 6P’s- 29hrs in sleep Lab. 7 of 20mins had to try to sleep. Sleep gate found in late evening where melatonin highest. This supports melatonin in sleep onset. Aschoff and Wever- p’s in WW2 bunker-4weeks- no external cues- circadian rhythm average=25hrs but some up to 29hrs.