Q.The hormone which regulates sleep and wake cycle is :

The pineal gland sits deep in the brain behind the third ventricle and secretes a single well-characterised hormone, melatonin. Melatonin's principal job is regulating the body's circadian rhythm — the roughly 24-hour cycle underlying the sleep-wake pattern, body temperature and appetite — and its secretion is tightly tied to light: it rises at night and is actively suppressed when light strikes the retina, which is the mechanism behind jet lag on l …