BIOL 4370 Lecture Notes - Autoimmune Disease, Multiple Sclerosis, Lipid Bilayer
16 Mar 2014
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Document Summary
Sept 19th: ap in somatosensory system are slow compared to mechanical wires. Axon is leaky: some of k can go out (via leaky channels) instead of being pushed/diffused (low resistance rm) Axon is sticky: when k+ tries to go down axon, they may be attracted and stick to negative ions through the membrane (high membrane capacitance cm) Axon is thin: diameter of axon is small and increases resistance slowing k to move (high axoplasmic resistance ra) Invertebrates evolved wide axons to speed up aps (low axoplasmic resitance) Disadvantage: not going to reach threshold as fast. Disadvantage: limits number of axons invertebrates can have: vertebrates evolved myelin (lipid bi-layer) to reduce leakiness and stickiness. Where this isn"t myelin is called nodes of ranvier . Acts as an insulation, covers up holes (leaky channels) and prevents positive and negative ions from attracting to each other by increasing distance. In nodes of ranvier there is high concentration of ion channels.
