Question

Multiple sclerosis (MS) is an autoimmune disorder in which the immune system destroys myelin sheaths surrounding axons. Which aspect of nerve transmission would be most affected by MS?

		signal termination
		continuous conduction
		generator potentials
		saltatory conduction

Answer 1

Multiple sclerosis affects the saltatory conduction of the impulse. In the presence of the myeline sheath, the electrical signal jumps from one myelinated segment to the next segment through the nodes of Ranvier. This is called saltatory conduction. Because of this feature, the nerve conduction will be very fast.

Multiple sclerosis is a demyelinating disorder of the Brain and spinal cord. Myeline is the protective sheath that covers the axon of the neuron making the electrical impulse transmission through the neuron more rapid. . The myelins are produced of oligodendrocytes which supports the neurons

In multiple sclerosis, the misguided immune system will attack these myeline sheath causing the destruction of myeline. This will cause for break down of the communication between the neurons leading to impaired sensory, motor and cognitive processes. The myelin-specific T-cells release cytokines like interleukin I, interleukin VI, tumor necrosis factor-alpha and interferon-gamma causes damage for the oligidendrocytes.These cytokines attracts B-cells and macrophages as a part of the inflammatory reaction. The B-cells will release the antibodies that will destroy the myeline sheath.Macrophages engulf and destroy the oligodendrocytes. This all results in loss of myeline covering the neuron leading to form a scar tissue or plaques around the neuron. The oligodendrocytes will then produce more myeline sheath to cover it again- remyelination. But progressively, since the oligodendrocytes re reducing in their number, the remyelination stops.Sometimes in severe cases, the neuronal axons may be damaged later on., which will lead to the irreversible damage of the nerve axon and thus stoppage of the conduction.