3. SCN-The Clock Regulates physiological functions Circadian Pacemaker - e.g. sleep/wake, core body temp. Temporal changes occur in a coordinated manner Light/Dark cycle is removed –free running Resetting of the clock External Time Cues - Zeitgebers
4.
5. Clock Timing Based on Gene expression Clock genes Clock, Per2, Per3 (there are others and vary among species) Reg. genetic transcription Negative feedback loop
6. Often Opposing Forces Homeostatic drive- ↑ with duration Adenosine buildup Circadian rhythm- cyclic ↑ in evening due in part to melatonin secretion
