PSY100Y5 Lecture Notes - Lecture 13: Circadian Rhythm, Sleep Deprivation, Jet Lag
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Biological rhythms - periodic and regular fluctuations in a biological systems such as body temp, sleep, activity, Circadian rhythm - a biological rhythm with a period of about 24 hours - latin "circa" about. "dies" day and are affected by all sorts of environment cues. Entrainment occurs where biological rhythms are synchronized with external cues, such as daylight. Studies in bunkers or caves (living without time cues) lead to "free-running" rhythms. Exposure to light triggers the lack of production of melatonin in order to entrain a rhythm. Without this our body will form their own cycles. Cycle is normally controlled by scn suprachiasmatic nucleus of hypothalamus- information from eyes. Leads to changes in levels of melatonin from pineal gland. Secreted during dark hours and keeps the sleep-wake cycle going . Melatonin also affects sexual activity cycle in hamsters. Blind people often have disrupted sleep-wake cycles, insomnia. Another external cue is hormones such as women with synchronous periods.
