Biological Rhythms for B and B

Biological Rhythms for B and B - BiologicalRhythms...

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Biological Rhythms
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Biological Rhythms  Terms  Diurnal- active during daytime Nocturnal- active during nighttime Crepuscular- primarily active at dawn and  dusk Evolution promotes restricting behaviors to  certain times Hormonal changes coincide with rhythms
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Biological Rhythms Chronobiology- scientific study of biological  clocks and their associated rhythms Rhythm- recurrent event characterized by: Period- time required to complete 1 cycle of  rhythm Frequency- # of completed cycles/unit of time Amplitude- amt of change above or below  average Phase- point in rhythm relative to some  objective time point during the cycle
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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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Biological clocks Exogenous vs Endogenous Control  Exogenous forces – forces outside of the  organism.  Endogenous timing mechanisms – those that  originate from inside the organism Certain behaviors indeed do disappear when  exogenous cues are not present, but others  continue or persist.  How can you tell the difference if a rhythm is  caused by exogenous or endogenous forces?
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Endogenous biological rhythms  Circadian rhythms Once about every 24  hours  Ex: the sleep-wake  cycle
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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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The Diversity of Biological  Rhythms
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Zeitgeber “Time Giver” The periodic  environmental cue that  synchronizes  endogenous biorhythm  to exogenous rhythms. Ex:  Light Entrainment – process  of synchronization What happens when  we don’t have  zeitgebers?
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Ex. Circadian Rhythm: Hamster running activity DARK LIGHT
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Experimenting with Light If you took a hamster who normally experienced lights  out at 8pm, you would consistently see that their activity  would begin between 8:05 and 8:15.   But what would happen if you started turning the lights  off 4 hours later, at midnight?   After four or five nights, you would see that the hamsters have  phase-shifted their activity to begin later. Circadian rhythms of other physiological processes such as 
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Biological Rhythms for B and B - BiologicalRhythms...

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