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PSY397 Oct 17

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University of Toronto St. George
Martin Ralph

Lecture Oct17 10/17/2012 7:11:00 AM Slide 2 –  Photoreception occurs in the eyes  In mammals, there are photoreceptors in the retina that are not visual cells o they receive information about light and dark Slide 3 –  Where is the clock? In the eye o Eye has been taken out of mouse, hamster – circadian rhythms free run in light cycle and dark cycle o Photoreception happens through the retina o ALL mammals o Now you can see what the retina projects to Slide 4 –  skipped Slide 5 –  already mentioned  skipped Slide 6 –  Evidence that retinal and pineal are involved in some way Slide 7 –  Looking at mammalian systems in general, we see that the whole system is an hierarchy oscillator  the SCN is connected to light and dark – the only oscillator  Single cells contain clocks now – their pays attention to what goes on in its environment  SCN pays attention to light and dark  We know how systems are generated – one is molecular clock, we also know there are oscillators that are generated by mechanism that are post-translational  Nervous system is built to accommodate all that goes around it to drive rhythmicity. Slide 8 –  Food entrainment  look for a system with multiple inputs  Lets the organism anticipate other things happening around it  Put somthing the animal desires, or is afraid of o evidence of other oscillators  exp. Food limited – mouse anticipates the food o mouse learns that environment isn’t predictable o circadian rhythm pays attention to light and dark o middle one: central clock is affected as mouse becomes hungrier Slide 9 –  Allows animal to antipciate something new in environment Skipped a bunch of lsides Most of all, tissues and cellsa re able to generate circnadian oscillations:  SCN Central circadian organization in mammals:  Lose light input into retina  Eye – becomes photoreceptor  SCN - becomes regulator  Everything else is feeding back  Tells SCN how well the system is working  Pineal is a feedback - melatonin modulates rhythm generation  SCN controls rhythms of behaviour o Which also feedbacks on SCN  Non-photic input and feedback by multiple pathways to generate rhthm o This means that the entire organism is a clock o Clock in SCN sends out signal and coordinated by all other things in
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