Which of the following voltages would most likely be measured during the relative refractory period?

Correct Answer: C

Rationale: During the relative refractory period, the membrane is hyperpolarized (more negative than resting potential, -70 mV) due to potassium efflux, but recovering. -45 mV is plausible, as it’s below threshold (-55 mV) but above full hyperpolarization.

Correct Answer: C

Rationale: The oculomotor nerve (CN III) supplies medial rectus, ciliary body, levator palpebrae superioris, and inferior oblique. The lateral rectus (option e) is innervated by the abducent nerve (CN VI), not CN III.

Correct Answer: B

Rationale: The anterior spinal artery (singular) arises from the vertebral arteries, supplying the anterior spinal cord. There are two posterior spinal arteries, typically from the posterior inferior cerebellar arteries, not superior cerebellar.

Correct Answer: C

Rationale: The trochlear nerve (CN IV) innervates only the superior oblique. The trigeminal (V) has motor and sensory roles, abducens (VI) exits via the superior orbital fissure, and hypoglossal (XII) exits via the hypoglossal canal.

Correct Answer: B

Rationale: The vagus nerve (CN X) arises from the medulla, with nucleus ambiguus fibers (shared with CN XI origins) for pharyngeal/laryngeal muscles. It doesn’t supply the diaphragm (phrenic nerve) or face.