Melatonin physiology (secretion pattern, receptors, lipid solubility)
Core concept
- Melatonin secreted by the pineal gland from tryptophan -> serotonin -> N-acetylserotonin -> melatonin (rate-limiting step: AANAT enzyme)
- Secretion driven by the suprachiasmatic nucleus (SCN) - the master circadian clock - via a multisynaptic pathway to the pineal
- Light suppresses secretion (via retinohypothalamic tract -> SCN -> inhibits sympathetic drive to pineal); darkness permits release -> secretion rises in the evening, peaks in the night, falls before waking
3 more sections, plus exam facts
Premium unlocks every note across every specialty, and the full exam fact library behind it.
Get premium access