PSYC 211 Chapter Notes - Chapter 9.9: Preganglionic Nerve Fibers, Pineal Gland, Pupillary Response
3 Jun 2016
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Document Summary
Circadian rhythms are the daily rhythms in behaviour and physiological processes. These rhythms are usually ones with a cycle of approx. 24h: some of these rhythms are passive responses to changes in illumination, and others are controlled by mechanisms within the organism, i. e. internal clocks. A free-running clock, with a cycle of about 25h, controls some biological functions, such as sleep and wakefulness: regular daily variation in levels of illumination normally keeps the clock adjusted to 24h. Our normal period of inactivity begins several hours after the dark portion of the day/night cycle and persists for a variable amount of time into the light portion, though this namely due to modern civilization. If we were kept in constant illumination, our biological clocks would run free and we would either gain or lose time. Most people have cycle lengths of about 25h, though there is some variability: morning light acts as a zeitgeber, and resets the clock.
