Sleep and Dreaming

Sleep and Dreaming - Biological Rhythms, Sleep and Dreaming...

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1 Biological Rhythms, Sleep and Dreaming Chapter 14 2 Biological Rhythms Biological rhythms are periodic changes that take place in living organisms. They range from second to minutes to months to years. Most important and well studied of these rhythms are the daily rhythms. 3 Circadian Rhythms Circadian rhythms, Circa (about) dies (day), have been studied in a host of animals at the behavioral, physiological and biochemical levels.
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4 Rhythm Activity One way to study daily rhythms is to engage an animal in an activity that varies over day-night cycle. 5 Animal Differences Rodents are nocturnal and humans and other primates are diurnal , i.e., rodents remain active during dark hours and humans remain active during light hours. 6 Endogenous Clocks If rodents like hamsters are placed in cages where light is kept constant, these hamsters maintain daily rhythm, suggesting that they have internal clocks.
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7 Free-Running Cycle Rodents may use other cues like outside noises, temperature and barometric pressure to reset their clocks. However, in such free-running cycle each day the daily rhythm begins a little later. 8 Internal Clock Daily rhythm of free-running nocturnal animals can be regulated by external stimulus like light. The shift in activity caused by light is called phase shift . Rhythm shift is called entrainment . The cue is called zeitgeber (time giver). 9 SCN Experimental investigations with the hypothalamus suggested that suprachiasmatic nucleus (SCN) was the internal clock. 1. SCN explants show rhythmic activity matched with light- dark cycle. 2. When fetal SCN was replaced in adult hamsters the cycle equaled 19.5 hours instead of 24.05 hours.
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10 SCN and Light SCN is directly entrained by light because optic nerve innervates this nucleus. 11 Other Rhythms 1. Many diverse rhythmic biological events have periods that are shorter than a day, called ultradian rhythms. These include bouts of activity, feeding behavior and hormone release. 2. Infradian rhythms include menstrual cycle, changes in weight, breeding behavior etc. These can be months to years long.
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This note was uploaded on 03/09/2010 for the course PSY 4293 taught by Professor Ahmad during the Fall '09 term at Henderson.

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Sleep and Dreaming - Biological Rhythms, Sleep and Dreaming...

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