BSC 2011 Lecture Notes - Lecture 17: Axon Hillock, Multiple Sclerosis, Membrane Potential
25 Feb 2015
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Document Summary
Bsc2011 - integrated principles of biology 2 - lecture 1: neurons and the nervous. Factors that affect the speed of action potential: Large axon diameter and myelin sheath increase the speed of action potential spreading. Resistance to current flow is reduced as diameter of axon increases. Vertebrates use a different strategy; they evolved myelin to insulate axons. Large diameter and myelin are different evolutionary solutions to the same problems. However, myelin is more effective at increasing action potenial without increasing diameter. The myelin sheath focuses current at nodes of ranvier and allows ion channels to be further spread apart. Multiple sclerosis is caused by the immune system attacking myelin. Neurotransmitters are synthesized in cell bodies, stored in axon terminals, and stimulated for release by action potentials and calcium. Neurotransmitters bind to receptor (ligand-gated) channels in the postsynaptic membrane and change ion flow and therefore membrane potential. Synapses cause postsynaptic potentials, which are graded, small, and decay with distance.
