PSYCH 330 Lecture Notes - Lecture 18: Ultradian Rhythm, Zeitgeber, Freerunning
27 Nov 2018
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Document Summary
Repeated, predictable changes over time, range from fast to slow. Circadian rhythm: 24 hr cycle, sleep behavior. Infradian rhythm: less frequent than circadian rhythm, menstrual cycle, seasonal breeding behavior. Ultradian rhythm: more frequent that circadian, feeding behavior, release of certain hormones. : pattern of behavioral/physiological fluctuation with a 24 hr period. Sleep, hormone release, digestion, body temp, muscle activity. Internal clock set by zeitgebers (external cues like light) Rhythms persist even without light dark cycle. Circadian scientists track hamsters" activity on a running wheel. In dim light, hamsters will start running every 25 hrs or so. Changing the zeitgeber will change the rhythm: phase shift. Shutting off the lights 1 hr later causes the hamsters to begin running 1 hr later. Humans phase shifted by changing time zones=jet lag. Consistent, free running period suggests that there must be some. Endogenous rhythms: natural rhythm controlled by some endogenous clock- scn in hypothalamus.
