Which of the following is not true about myelination?

Question

BlackTom AI · Accepted Answer

First, let's restate the question and options to set the stage for analysis.
Question: Which of the following is not true about myelination?
Options:
1) It consists of glial cells called oligodendrocytes and Schwann cells
2) Deterioration of myelin causes multiple sclerosis
3) Action potentials are propagated in between myelin cells at points called Nodes of Ranvier
4) It increases the speed of the propagation of the action potential down the axon
5) It is only found in the peripheral nervous system

Now, evaluate each option on its own merits and relate it to what is known about myelination.
Option 1: It consists of glial cells called oligodendrocytes and Schwann cells. This statement is largely true, because oligodendrocytes are the myelinating glia in the central nervous system (CNS), while Schwann cells perform myelination in the peripheral nervous system (PNS). The idea that myelin is produced by these glial types is accurate, though the wording lumps both cell types together; it is still a true statement about the cellular players involved in myelination across CNS and PNS.
Option 2: Deterioration of myelin causes multiple sclerosis. This is a true statement. Multiple sclerosis is characterized by demyelination, which disrupts efficient nerve conduction and underlies various neurologic symptoms.
Option 3: Action potentials are propagated in between myelin cells at points called Nodes of Ranvier. This statement is essentially true in the context of saltatory conduction. The action potential travels rapidly along the insulated (myelinated) segments and regenerates at the Nodes of Ranvier, which are gaps between adjacent myelin sheaths where voltage-gated channels are concentrated.
Option 4: It increases the speed of the propagation of the action potential down the axon. This is a fundamental property of myelination—myelin increases conduction velocity by reducing membrane capacitance and allowing saltatory conduction, so this statement is true.
Option 5: It is only found in the peripheral nervous system. This is not true. Myelination occurs in both the CNS and PNS: oligodendrocytes in the CNS form myelin, and Schwann cells in the PNS form myelin. Therefore, the claim that myelin is exclusive to the peripheral nervous system is incorrect.

In summary, the incorrect statement is option 5, which asserts that myelination is found only in the peripheral nervous system. The other options accurately reflect key aspects of myelination, including its cellular mediators across CNS and PNS, the role of demyelination in MS, the mechanism of saltatory conduction at Nodes of Ranvier, and the speed enhancement conferred by myelin.

Which of the following is not true about myelination?单项选择题

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Question at position 32 Schwann cells primarily:Wrap around axons to form myelin sheathsCover axons without gaps for continuous insulationInsulate the central nervous system axonsRegulate the extracellular environment of neuron cell bodies

The axons of peripheral system neurons are surrounded by cells called They wrap the axon in many layers of a whitish, non-conductive protein called . Without this coating, the electrical impulse that propagates the nerve signal can be lost to the surrounding tissue.

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