Poultry_Science_2-1 - - Zeitgeber. How light entrains on a...

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How does a bird time its daily and seasonal activities?  Daily: Light temperature. Seasonal:  Day length, Temperature, Food availability   Animals tend to get entrained. An environmental factor will regulate an  animal’s activity timely.    Circadian rythym becomes: FREE-RUNNING  Free- running circadian cycles: when they drift away from the regular  cycle.  The fact that birds keep approx. 24 clock shows that there is an annate  internal clock. (mechanism for keeping approx. 24 hr cycle w/o external cues)  Endogenous circadian rhythm.  Entrainment: using environmental cues to fine-tune circadian rythym.  Zeitgeber: an entrainer (literally “time giver”)                  A cue used by animals to set circadian rythym.   Circadian rythym require both  -Innate internal clock 
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Unformatted text preview: - Zeitgeber. How light entrains on a physiological basis: In mammals Pineal Gland (produces melatonin that effects hp) is main pace maker. However in birds it has a little less effects. Its right on top of the heads in birds. So light may effect it directly. Hypothalamic pacemaker superchiasmatic Nucleus (SCN) this is the main pacemaker and is located in the hypothalamus. A nucleus is the center of many neurons. Mammals dnt have the extraretinal/extrapineal recepto (controls neural activity)r. It responds to light. EYE-----melatonin LIGHT----- Extra retinal/extrapineal receptor SCN --- daily circadian activ. Pineal----melatonin...
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This note was uploaded on 04/08/2011 for the course POUL 3123 taught by Professor Navara during the Spring '09 term at University of Georgia Athens.

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