2. Myelin is a mixture of proteins and phospholipids important for conduction of

Question

2. Myelin is a mixture of proteins and phospholipids important for conduction of action potentials along long axons. In particular, myelin sheaths are responsible for saltatory conduction, resulting in increased conduction speeds of action potentials. Answer the following questions about myelin. (a) Explain how myelination increases conduction velocity. In particular, what happens to the membrane resis- tance, Tm, and membrane capacitance, cm, of the axon. (b) What cells produce myelin in the Central Nervous System (CNS)? In the Peripheral Nervous System (PNS)? (c) Discuss one clinical pathology in which myelination is affected. What is its pathogenesis?

Explanation / Answer

Ans a:- myelin is an insulating layer which helps to conduct signal at a much faster rate.a neuron depolarize when there is influx of sodium ion.during the transmission of action potential one node is repolarising and the next one is depolarising.the myelin sheith contain breaks called nodes of ranvier.by jumping from nodes to nodes it can travel more quickly than traveling the whole lenth.subsequent action potential occur at the nodes of ranvier where sodium channel are located.the membrane resistance decreases and the membrane capacitence increases.

Ans b:-CNS:-oligodendrocytes

   PNS:-schwann cells

c:-Multiple sclerosis is a well known disease where myelination is affected.There is damage to the myelin sheath due to inflamation.

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