This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Melatonin is secreted by \nSelect and explain. \nA. Hypothalamus, B. Adrenal coex, C. Pineal gland, D. Melanocytes', 'role': 'user'}, {'content': "Answer: C \nExplanation: Retinohypothalamic fibers synapse in the suprachiasmatic nuclei (SCN), and there are connections from the SCN to sympathetic preganglionic neurons in the spinal cord that project to the superior cervical ganglion. Postganglionic neurons project from this ganglion to the pineal gland that secretes melatonin. The cyclic activity of SCN sets up a circadian rhythm for melatonin release. This rhythm is entrained to light/dark cycles by neurons in the retina.(Ref: Ganong's Review of Medical Physiology Twenty-Third Edition)", 'role': 'assistant'}]