PHGY 209 Lecture Notes - Lecture 13: Voltage-Gated Potassium Channel, Chemical Synapse, Upper Set

• School: McGill University
• Department: Physiology
• Course: PHGY 209
• Professor: Ann Wechsler

Document Summary

Propagation of electrical impulses: axons (axons propagate action potentials) Initial segment: part of axon where action potentials start. Analogous to a long rope . you whip one end of the rope, the wave travels down the length of the rope. The action potential = a transient depolarizing spike that moves down the axon. At action potential peak: membrane potential approaches ena. Note that at rest, the entire neuron (from dendrites to cell body to axon) is at -70mv. Potential depolarizes to threshold level (-50mv; actually differ b/w diff. types of neurons) Threshold: determined by properties of ion channels in the axon membrane. If you don"t get to threshold, no action potential. Action potentials don"t vary in size, don"t vary in strength, don"t vary in duration. Voltage-gated sodium channels (rise) depolarization => na+ in. Open channel rapidly inactivates, stopping flow of na+ ions quickly. The more depolarized the neuron gets, the more sodium channels.