Light Dark Mechanism of the Suprachiasmatic Nucleus

The video explains how the suprachiasmatic nucleus (SCN) regulates melatonin release from the pineal gland. It details the pathways activated by light and darkness, focusing on the role of intrinsically photosensitive retinal ganglion cells (IP RGCs) and the retino hypothalamic tract. The SCN inhibits melatonin release during the day by activating the dorsomedial hypothalamic nucleus and the intermediolateral nucleus, which in turn inhibit the superior cervical ganglion. At night, the absence of light allows the superior cervical ganglion to activate the pineal gland, releasing melatonin. An alternative pathway involving the paraventricular nucleus is also discussed.

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