Problem Set / Case Study #3 1. A nerve cell has an axon that extends 3 cm with a

Question

Problem Set / Case Study #3 1. A nerve cell has an axon that extends 3 cm with an inter-node spacing of 2 mm.- Calculate the membrane potential at a node just prior to the generation of an action potential given the following information: Membrane length constant- 1 mm Threshold- 35 mV Resting membrane potential (RMP)--60 mV Action potential overshoot +20 mV. What is the membrane potential at the next node, and is depolarization sufficient to generate another action potential? % Response = 100(1-et) a. 49 mV, and an AP will NOT occur at node 2 b. -30 mV, and an AP WILL occur at node 2 c. -69 mV, and an AP WILL occur at node 2 d. -25 mV, and an AP will NOT occur at node 2 2. Explain how the length constant is affected following degradation of the myelin sheath, or in other words, how is the length constant affected by decreases in membrane resistance (Rm)? How does demyelination affect conduction along the axon? 3. Name one disease that causes demyelination.

Explanation / Answer

2.

Demyelination affects conduction of nerve impulse along axon .Due to Demyelination, the membrane permeability increase at each point and impulse transmits slowly. Jumping of impulse from one node to another is not possible at node of ranvier or the process of saltatory conduction is not possible hence conduction along the axon decreases.

Thus demyelination affect the nerve conduction by decreasing rate of impulse flow. In some cases demyelination leads to blocks the impulse flow.

3. Demyelination is the damage to protective covering of nerve fibre . Multiple sclerosis is a good example of demyelination disease due to body own immune disfunction. Optic neuritis is another example related to eye.

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