SCIENCE
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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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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the spread of action potential down the axon
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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: -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 potentials in unmyelinated axons propagate continuously. In contrast, myelinated axons are electrically insulated, which means no ion exchange happens where myelin is wrapped around. Between myelin sheaths are gaps called nodes of Ranvier, where voltage-gated ion channels are located.
Detailed explanation-3: -In unmyelinated axons, the action potential travels continuously along the axons. For example, in unmyelinated C fibers that conduct pain or temperature (0.4–1.2 m in diameter), conduction velocity along the axon is 0.5–2.0 m/s (as fast as you walk or jog).
Detailed explanation-4: -a. Describe continuous conduction along an unmyelinated sheath. The step-by-step depolarization of an axon and generation of action potentials sequentially along the entire length of a nerve fiber is called continuous conduction.