The master circadian clock in mammals, which synchronizes sleep-wake cycles to the light-dark cycle, is located in which structure?
- A Pineal gland
- B Lateral hypothalamic area
- C Suprachiasmatic nucleus of hypothalamus ✓
- D Ventrolateral preoptic nucleus
Correct answer: C. Suprachiasmatic nucleus of hypothalamus
Explanation
The suprachiasmatic nucleus (SCN) of the hypothalamus is the master circadian pacemaker. It receives direct retinal input via the retinohypothalamic tract and synchronizes circadian rhythms to the 24-hour light-dark cycle. The pineal gland secretes melatonin under SCN control but is not the master clock itself.
Reference: Ganong's Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.