11 - Biological Rhythms

11 - Biological Rhythms - Biological Rhythms What are...

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Biological Rhythms
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What are Biological Rhythms? Rhythmic fluctuations in behavior and activity that occurs in all living things Controlled by internal processes Controlled by external stimuli Ex. Earth’s rotation around Sun
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Fig. 12-1
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What drives behavior? Behavior is not simply driven by external cues. Rhythms are endogenous (comes from within) Biological Clock Neural system that times behavior Allows animals to anticipate events before they happen Ex: Bird migration
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Periods of Activity Circannual- yearly Ex: bird migration Infradian- more than a day, less than a year Menstrual Cycle Circadian- daily- Human sleep cycle Ultradian- less than a day Eating cycle, heart rate,
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Endogenous biological rhythms Circadian rhythms Once about every 24 hours Ex: the sleep-wake cycle
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Ex. Circadian Rhythm: Hamster running activity DARK LIGHT
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Zeitgeber Environmental cue that entrains biological rhythms “time giver” Ex: Light Entrainment Determination or modification of biorhythm period What happens when we don’t have zeitgebers?
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Free-Running Period Body’s own rhythm created in the absence of zeitgebers Humans: rhythms of ~25 to 27 hours Sleep-wake cycle shifts an hour or so everyday Proof of endogenous rhythms
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Aschoff and Weber Study: Fig. 12-3
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Free-running activity still depends on external cues In diurnal animals: DD: free-running is longer than 24 hrs Phase delay LL: free-running is shorter than 24 hrs Phase advance
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Fig. 12-4
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Effects of Free Running 1. Seasonal affective disorder Person experiences depression during Winter and improvement in the Spring. May not be properly entrained ~0.4 -20% occurrence rate Treatment involves phototherapy or exposure to fluorescent light.
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Effects of Free Running 2. Jet Lag Time/light change → disruption in entrainment The body's natural pattern is upset Rhythms that dictate times for eating, sleeping, hormone regulation and body temperature variations no longer correspond to the environment West to east traveler: harder to adjust
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Neural Basis of the Biological Clock
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Neural Basis of the Biological Clock Biological clock: pacemaker that instructs neural structures to produce behavior in a rhythmic fashion “Clock” is located in the hypothalamus Suprachaismatic nucleus (SCN) In the hypothalamus Above (supra) to optic chiasm
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11 - Biological Rhythms - Biological Rhythms What are...

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