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. Author manuscript; available in PMC: 2010 Sep 1.
Published in final edited form as: Gen Comp Endocrinol. 2009 Jan 23;163(1-2):109–116. doi: 10.1016/j.ygcen.2009.01.003

Figure 2.

Figure 2

Schematic of the interactions of circadian pacemakers within the avian circadian system. The pineal gland and retina, each directly photosensitive, release melatonin during the night, which inhibits SCN activity. Conversely, as day approaches, oscillators in the pineal gland and retina wane in their outputs, disinhibiting the SCN, which become active during subjective day, inhibiting pineal output via the sympathetic autonomic nervous system. It is not known whether the SCN directly affect retinal function.