MCAT Behavioral Sciences Question 181: Answer and Explanation

Home > MCAT Test > MCAT behavioral sciences practice tests

Test Information

Question: 181

1. A demyelinating disorder, such as multiple sclerosis, would cause all of the following symptoms EXCEPT:

  • A. a reduction of white matter in the central nervous system.
  • B. increased saltatory conduction.
  • C. slower propagation of signals along the axon.
  • D. a deficiency of sensation.

Correct Answer: B

Explanation:

Myelin is an insulating sheath wrapped around the axons of neurons. White matter in the central nervous system is composed of myelinated axons; thus, a reduction in myelination would result in a decrease in white matter (choice A is a symptom and can be eliminated). Gaps in the myelin sheath (called nodes of Ranvier) allow depolarization of the axon and conduction of neuronal signals along the length of the axon. Myelination speeds the movement of the action potential along the length of the axon (choice C would be a symptom and can be eliminated), in a process called saltatory conduction; a reduction in myelination would decrease (not increase) saltatory conduction (choice B is not a symptom and is the correct answer choice). This would decrease sensation, as sensory information from the peripheral nervous system would be hindered from reaching the central nervous system (choice D is a symptom and can be eliminated).

Previous       Next