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Circadian Rythms

In: Philosophy and Psychology

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States of Consciousness: Sleep Deprivation

States of Consciousness: Sleep Deprivation
Michelle Rogers
ITT Technical Institute

Circadian rhythms are regular changes in mental and physical characteristics that occur in the course of a day (circadian is Latin for "around a day"). Most circadian rhythms are controlled by the body's biological "clock." This clock, called the suprachiasmatic nucleus or SCN, a pair of pinhead-sized brain structures that together contain about 20,000 neurons. The SCN rests in a part of the brain called the hypothalamus, just above the point where the optic nerves cross. Light that reaches photoreceptors in the retina (tissue at the back of the eye) creates signals that travel along the optic nerve to the SCN.
Signals from the SCN travel to several brain regions, including the pineal gland, which responds to light-induced signals by switching off production of the hormone melatonin. The body's level of melatonin normally increases after darkness falls, making people feel drowsy. The SCN is synchronized with the sleep/wake cycle, including body temperature, hormone secretion, urine production, and changes in blood pressure.
Sunlight or other bright lights can reset the SCN, our biological cycles normally follow the 24-hour cycle of the sun, rather than our innate cycle. Circadian rhythms can be affected to some degree by almost any kind of external time cue, such as the beeping of your alarm clock, the clatter of a garbage truck, or the timing of your meals. Scientists call external time cues zeitgebers (German for "time givers").
Circadian rhythms is the sleep/wake cycle. Chronic circadian rhythm sleep disorders are internal abnormalities of the circadian rhythms, the body’s internal clock. This arises when a person is unable to fall asleep at normal bedtime (late evening), although he/she can sleep at other times.
The delayed…...

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