This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thalamus, Hypothalamus and Basal Ganglia, Subject name: Physiology
Body clock is maintained by - 
Select and explain. 
A. Suprachiasmatic nucleus, B. Supraoptic nucleus, C. Ventrolateral nucleus, D. Thalamus
A: Suprachiasmatic nucleus
Answer: A: Suprachiasmatic nucleus 
Explanation: Ans. is 'a' i.e., Suprachiasmatic nucleus o A person's circadian rhythm is an internal biological clock that regulates a variety of biological processes according to an approximate 24-hour periods. Several body functions show a circadian (24 hour) rhythmo These functions include feeding, drinking, locomotor activity, sleep, corticosteroid secretion, body temperature and melatonin secretion by the pineal. Most of these functions are regulated by the hypothalamus.o Suprachiasmatic nucleus of the hypothalamus is believed to contain the "biological clock", which regulates the circadian rhythms according to the light dark cycles.