BIOL 3P34 Lecture Notes - Lecture 13: Myelin, Saltatory Conduction, Multiple Sclerosis
7 Nov 2016
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Document Summary
Not only electrotonic spread of graded potentials in dendritic tree. Rapid action potential propagation is important, how is it achieved: increasing the diameter of axonal core, saltatory conduction: myelination of axons. Nodes of ranvier are interruptions in the myelin sheath. They are densely populated with na channels. Diam : speed velocities vary, myelinated axons of shrimp have the highest velocities. Aps develop only at nodes of ranvier (myelin restricts current flow) Velocity, myelinated axons are also capable of firing faster and longer. Multiple sclerosis: chronic disease of the central nervous system, characterized by areas of demyelination of the brain and spinal cord axons. Demyelination has dramatic effects on nerve fibers: saltatory conduction is more energy efficient than conduction along the entire length of axon, loss of myelin causes one or more of: Blood brain barrier is disrupted at the onset of symptoms. Acute inflammatory response of lymphocytes and macrophages produce demyelination by direct or indirect mechanisms.
