Lower motor neuron disease is characterized by:

Correct Answer: A

Rationale: Lower motor neuron disease causes wasting (A), weakness, and hyporeflexia, not hypertonia (B), hyperreflexia (C), or clonus (D, upper motor signs). A is correct.

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: B

Rationale: The third ventricle (B) lies within the diencephalon, between the thalami. Lateral ventricles (A) are in the telencephalon, cerebral aqueduct (C) in the midbrain, and fourth ventricle (D) between pons and cerebellum. B 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.