PATHOLOGY MCQ
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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more rapidly in myelinated than in non-myelinated axons.
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by reversing the concentration gradients for sodium and potassium ions
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more slowly in axons of large than in small diameter
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by the direct action of acetylcholine on the axonal membrane
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Detailed explanation-1: -By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). For example, whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.
Detailed explanation-2: -Action potential propagation in myelinated neurons is faster than in unmyelinated neurons because of saltatory conduction.
Detailed explanation-3: -In unmyelinated axons, the action potential travels smoothly, with constant shape and at constant velocity. In myelinated axons, conduction is saltatory: The action potential “jumps” nearly instantaneously from one node of Ranvier to the next, greatly increasing the speed of propagation.