Demyelination of an axon:
A. Results in decreased membrane resistance, allowing a leakage of electrical current.
B. Results in slowed propagation of action potentials.
C. May prevent propagation of action potentials.
D. Both A and B
E. A, B, and C
ANS: E
Rationale: Myelination increases the speed of action potential propagation and the distance a current can passively spread. Thicker myelin leads to faster conduction and improved action potential propagation. Demyelination allows leakage of electrical current across the membrane, decreasing the amplitude and velocity of the signal as the action potential travels down the axon. Similarly, when a hose has a leaky wall, the flow diminishes as the distance from the faucet increases.
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