Question

question 29
gray matter in the cns contains __, whereas white matter contains __.
axons, neuron cell bodies
ascending fibers, descending fibers
cell bodies with melanin, cell bodies without melanin
neuron cell bodies and dendrites, axon fibers

Explanation:

To solve this, we recall the structure of gray and white matter in the CNS (Central Nervous System). Gray matter is composed of neuron cell bodies, dendrites, and unmyelinated axons. White matter consists mainly of myelinated axon fibers (which give it the white appearance due to myelin). Let's analyze each option:

• First option: Swaps the components (axons are in white matter, cell bodies in gray), so incorrect.
• Second option: Ascending/descending fibers are part of white matter, but this doesn't define gray/white matter's main components, so incorrect.
• Third option: Melanin has no relation to gray/white matter distinction, so incorrect.
• Fourth option: Matches the correct composition (gray matter: neuron cell bodies and dendrites; white matter: axon fibers).

Answer:

D. neuron cell bodies and dendrites, axon fibers