Question

5.

Briefly discuss the structure of myelin and its role in the nervous system (biochemistry

connection to the lecture content)

Answer 1

The mylein sheath is a greatly extended and modified plasma membrane wrapped around the nerve axon in spiral fishion, made up of phospho lipids, cholesterol and proteins.The myelin membranes are originate from and are part of the schwann cell in the peripheral nerve system.and the oligodendroglial cells in the central nerve system.

Electron microscopy studies showed protein layers which are separated by lipid hydrocarbon chain.However the difference in periodicty bitween the PNS and CNS mylein is mantained peripheral mylein has a average repeat distance of 199 angstroms and central mylein 107 angstroms.

Mylein is an electrical insulator however its function of facilitating the conduction on exons has no exact analogy in electrical sircuitry. The myelin sheath has number of functions in the nervous system. the main function includes protecting the nerves from electrical impulses and speeding the time it takes for a nerve traverse an axon.The myelin sheath does not allow the action potential where it covers the axon, insted a critical wave created at each node propels the action potential to the end of the nerve, where it can be transfared to the next neuron.This mode of propagating signal down the exon also saves energy as the sodium potassium that ragulates the action potential are not needed under the myelin sheath.