Chapter 5 - 1Chapter 5: Body Rhythms and Mental States...

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1Chapter 5: Body Rhythms and Mental States Interactive Lectures 1. Biological Rhythms: The Tides of Experience Consciousness is the awareness of oneself and the environment. Changing states of consciousness are often associated with biological rhythms - periodic fluctuations in physiological functioning. These rhythms are typically entrained (synchronized) to external cues, but many are also endogenous , generated from within. Circadian fluctuations occur about once a day; other rhythms occur less frequently or more frequently than that. When people live in isolation from all time cues, they tend to live a day that is just slightly longer than 24 hours. Circadian rhythms are governed by a biological "clock" in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN regulates, and in turn is affected by, the hormone melatonin , which is responsive to changes in light and dark, and which increases during the dark hours. When a person's normal routine changes, the person may experience internal desynchronization , in which the usual circadian rhythms are thrown out of phase with one another. The result may be fatigue, mental inefficiency, and an increased risk of accidents. Folklore holds that moods follow infradian cycles. Some people do show a recurrence of depression every winter, in a pattern that has been labeled seasonal affective disorder (SAD), but serious seasonal depression is rare. The causes of SAD are not yet clear, and it has been difficult to rule out placebo effects in the most common treatment, phototherapy. However, recent research suggests that light treatments can be effective. Another infradian rhythm is the menstrual cycle, during which various hormones rise and fall. Well-controlled double-blind studies on "PMS" do not support claims that emotional symptoms are reliably and universally tied to the menstrual cycle. Overall, women and men do not differ in the emotional symptoms they report or in the number of mood
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Chapter 5 - 1Chapter 5: Body Rhythms and Mental States...

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