What type of glial cell provides myelin for the axons in a tract?

Correct Answer: A

Rationale: Oligodendrocytes provide myelin for axons in the central nervous system (CNS), where tracts are located. Schwann cells myelinate axons in the peripheral nervous system (PNS), astrocytes support neurons, and satellite cells support cell bodies in the PNS.

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: The middle cerebral artery (MCA) is the largest branch of the internal carotid artery, supplying a significant portion of the cerebral cortex (e.g., lateral aspects). The ophthalmic artery is smaller, and the anterior cerebral and striate arteries are not as large.

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.