PATHOLOGY MCQ
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the spread of action potential down the axon
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along myelinated axons it moves at a speed of about 18-140 meters per second (18-140 mph)
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along unmyelinated axons it moves at a speed of about 1 meter per second (2 mph)
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None of the above
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Detailed explanation-1: -The propagation of electrical impulses along axons is highly accelerated by the myelin sheath and produces saltating or “jumping” action potentials across internodes, from one node of Ranvier to the next.
Detailed explanation-2: -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-3: -The myelin sheath increases axonal conduction velocity by reducing capacitance of the axonal membrane and allowing saltatory conduction (Hodgkin, 1964; Stampfli, 1954). Thus, myelinated axons of small diameter can transmit information as rapidly as much larger unmyelinated axons.