Answer: Brain.
- A Neck
- B Brain
- C Abdomen
- D Pelvis
Correct answer: B. Brain
Explanation: The pineal gland lies in the brain and secretes melatonin, which regulates the sleep-wake rhythm.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Concept context
The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.