This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Misc., Subject name: Physiology
Circadian rhythm is regulated by\ 
Select and explain. 
A. Supra chiasmatic nucleus, B. Neurohypophysis, C. Medulla, D. Pallidohypothalamic nucleus
A: Supra chiasmatic nucleus
Answer: A: Supra chiasmatic nucleus 
Explanation: (A) Supra chiasmatic nucleus # CIRCADIAN RHYTHM is a roughly-24-hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria.> Circadian system 3 major components: Central oscillator or pace maker Afferent pathways which carry entraining environmental information to the oscillator Efferent pathways that communicate the rhythmicity of the oscillator to the physiology and behavior of the organism.> Circadian "clock" in mammals is located in the suprachiasmatic nucleus (SCN), a distinct group of cells located in the hypothalamus.> Destruction of the SCN results in the complete absence of a regular sleep/wake rhythm.> SCN receives information about illumination through the eyes.