Describe circadian rhythms and the roles played by the SCN, clock proteins, melanopsin, and melatonin to control them
What will be an ideal response?
A circadian rhythm is repetitive oscillations in hormone levels that are very regular and cycle once every 24 hours. The SCN (suprachiasmatic nucleus) in the hypothalamus synthesizes clock proteins that accumulate during part of the day, but then decrease in concentration due to negative feedback. The fluctuating levels of clock proteins lead to cyclic changes in effector organs throughout the day. Melanopsin is a protein, found in certain ganglion cells of the eye, that enables these cells to cue to the SCN about the absence or presence of light. In turn, the SCN relays this information to the pineal gland, which secretes melatonin that helps keep the body's circadian rhythms synchronized with the light-dark cycle. More melatonin is secreted in the dark and plays an important role in promoting sleep.
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