What region of the diencephalon coordinates homeostasis?

Correct Answer: C

Rationale: The hypothalamus (C) regulates homeostasis (e.g., temperature, hunger, thirst). The thalamus (A) relays sensory/motor signals, epithalamus (B) includes the pineal gland (circadian rhythms), and subthalamus (D) aids motor control. C is correct.

Correct Answer: A

Rationale: White matter in the brain is primarily composed of myelinated axons, which are nerve fibers coated with myelin to speed up signal transmission. Neuronal cell bodies dominate gray matter, not white matter. Ganglia and dendrites from the enteric nervous system are not primary components of brain white matter.

Correct Answer: A

Rationale: Microglia are the resident macrophages of the CNS, acting as immune cells behind the blood-brain barrier. Astrocytes support neurons, Schwann cells myelinate PNS axons, and satellite cells support PNS cell bodies.

Correct Answer: B

Rationale: Voltage-gated Na⁺ channels open when the membrane potential reaches the threshold (around -55 mV), triggering an action potential. They don’t open at resting potential, during repolarization, or at overshoot.

Correct Answer: D

Rationale: Acetylcholine (ACh) is released at the neuromuscular junction to stimulate skeletal muscle contraction. Norepinephrine acts at sympathetic synapses, not the neuromuscular junction.