In multiple sclerosis the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does this disease manifest at the level of the action potential?
I. Action potentials move in the opposite direction on the axon.
II. Action potentials move more slowly along the axon.
III. No action potentials are transmitted.
A) only I
B) only II
C) only III
D) only II and III
E) only I and II

Question

Quizplus · Accepted Answer

In multiple sclerosis, the damage to the myelin sheath slows down the conduction velocity along the axon, resulting in a slower transmission of action potentials. However, the direction of the action potential remains the same, so I is incorrect. Although demyelination can lead to a reduction in the number of functioning axons, in most cases, some action potentials can still be transmitted, so III is also incorrect. Thus, the correct option is only II.

In Multiple Sclerosis the Myelin Sheaths Around the Axons of the Brain