BISC 230Lgx Lecture Notes - Lecture 20: Djungarian Hamster, Freerunning, Lightdark
9 Apr 2016
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Biological rhythms: regular luctuaions in a living process. Ultradian rhythms - more than once a day. Infradian rhythms - less than once a way. In the lab, only turns white when exposed to light 10 hours a day (infradian rhythm) Monitor when a mouse/rat is running on an exercise wheel (when it"s awake) Phase shit: circadian rhythm changes when the ime of light/dark is shited earlier or later, synchronizing simulus is applied. If constantly exposed to dim light, hamster becomes acive a few minutes later each day o. Natural circadian rhythm is a litle longer than 24 hours. Free-running period: maintaining a cycle with no external cues. Superachiasmaic nucleus (scn) in the hypothalamus controls circadian oscillaion (above the opic chiasm) Input from the reinohypothalamic pathway (light) goes to the scn. Normal human cycle is 25 hours, but sun trains us to have 24 hour cycles. Reina --> melanopsin (reinal ganglion cells) --> opic nerve --> scn.
