Mini MCAT passage: Demyelinating disease and aging

A scientist is studying a mouse model of peripheral demyelinating disease. The mice gradually lose myelin in their peripheral nervous sytem and develop neurological abnormalities. The scientist is able to electrically stimulate nerves in the mice to cause action potentials in axons and record the electrical response farther away on the nerve closer to where the axons enter the central nervous system.

The scientist hypothesizes that the number of action potentials conducted along each axon is related to the loss of myelin. He proposes to test this with two experiments. The first involves comparing the speed of action potential conduction in the nerves of younger and older mice with the disease. The second involves comparing the speed of action potential conduction in the nerves of mice with the disease and mice without the disease after a period of frequent electrical stimulation of the nerves.