Which of the following cavities contains a component of the central nervous system?

Correct Answer: C

Rationale: The central nervous system (CNS) consists of the brain and spinal cord. The cranial cavity houses the brain, making it the correct choice. The abdominal cavity contains digestive organs, the pelvic cavity contains reproductive and urinary organs, and the thoracic cavity contains the heart and lungs—none of which include CNS components.

Correct Answer: A

Rationale: Depolarization occurs when sodium (Na⁺) ions enter the neuron through voltage-gated channels, making the membrane potential more positive. Potassium exits during repolarization, and chloride or phosphate don’t typically drive depolarization.

Correct Answer: C

Rationale: When a negative ion (e.g., Cl⁻) enters, the membrane potential becomes more negative, causing a hyperpolarizing graded potential (inhibitory postsynaptic potential, IPSP).

Correct Answer: A

Rationale: The abducent nerve (CN VI) emerges at the pontomedullary junction, innervating the lateral rectus muscle. The facial (VII) and vestibulocochlear (VIII) nerves emerge from the pons, while glossopharyngeal (IX) emerges from the medulla.

Correct Answer: D

Rationale: The motor nucleus of the trigeminal nerve (CN V) is in the pons, near the floor of the fourth ventricle (option e). The hypothalamus and cortex don’t house motor nuclei, and the midbrain contains CN III/IV nuclei.