Anatomy and Cell Biology 4451F/G Lecture Notes - Lecture 7: Axon Hillock, Chemical Synapse, Dendrite

• School: Western University
• Department: Anatomy and Cell Biology
• Course: Anatomy and Cell Biology 4451F/G
• Professor: All

Document Summary

Active conduction of signals: axons drawn in textbooks are not representative of real axons. Real axons are much thinner and longer than the ones drawn: soma: 20 microm, dendrite length: 200 microm, axon length: 1-100 cm. If soma would be 10 cm, axon would be 5 km: action potential needs to pass along axon and since it is really thin, this means that the internal resistance is really high. Before you even get a real change in voltage, the potential may have already stopped. Thus, action potentials do not spread passively through axons. The action potential: driven by activation of voltage-gated ion channels (at the axon hillock, point of decision, active signal (membrane conductance change, all-or-none potential (hodgkin-huxley cycle) Epsp that passively spreads through dendritic trees and this is what arrives at the axon hillock of the epsp. Most epsps are strongly attenuated by the time they reach the axon hillock, no ap.