Which statement correctly describes the pathophysiology of multiple sclerosis?

• A. The dendrites on the neuron are overstimulated leading to destruction of the axon.
• B. The myelin sheath, which is made up of Schwann cells, is damaged along the axon.
• C. This disease affects the insulating structure found on the neuron in the central nervous system.
• D. The dopaminergic neurons in the part of the brain called substantia nigra have started to die.

Answer: (C)

Multiple sclerosis is an autoimmune process that targets the myelin sheath surrounding neurons in the central nervous system. In the CNS, myelin is produced by oligodendrocytes, not Schwann cells (which make myelin in the peripheral nervous system). When this myelin is damaged, nerve impulses travel more slowly or fail to propagate, producing the neurologic symptoms characteristic of MS. The disease often forms demyelinated plaques and involves inflammation and gliosis, with episodes that can occur at different times and in different locations.

That’s why the statement describing the insulating structure found on CNS neurons being damaged best fits MS. The other ideas don’t align: Schwann cells aren’t involved in CNS myelin, loss of dopaminergic neurons in the substantia nigra points to Parkinson disease, and dendritic overstimulation is not the primary mechanism of MS.