Which of the following is probably going to propagate an action potential fastest?

Correct Answer: D

Rationale: A thick, myelinated axon propagates action potentials fastest due to saltatory conduction (myelin) and lower resistance (thickness). Myelination speeds conduction more than diameter alone.

Correct Answer: C

Rationale: Central cord syndrome (often cervical) damages the central spinal cord, affecting motor (upper limbs > lower) and pain/temperature sensation, while touch sensation (dorsal columns) often remains intact due to its peripheral location.

Correct Answer: D

Rationale: Motor nerve fibers (alpha motor neurons) are large, myelinated, and typically 12-20 micrometers in diameter to ensure fast conduction to muscles. Smaller diameters are for sensory or unmyelinated fibers.

Correct Answer: B

Rationale: The facial nerve (CN VII) doesn’t supply the ciliary ganglion (CN III does via parasympathetic fibers). It supplies facial muscles, buccinator, taste (anterior 2/3 tongue), and the greater petrosal nerve.

Correct Answer: B

Rationale: The sensory root of CN VII is the nervus intermedius, carrying taste and parasympathetic fibers, exiting via the internal acoustic meatus, not foramen ovale.