PHGY 209 Lecture Notes - Lecture 4: Phyllobates, Tetraodontidae, Pyrethroid

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

Document Summary

The membrane potential is determined by concentration gradients and relative permeabilities of membrane to different physiological ions. The dominant permeability makes greatest contribution to the membrane potential. (at rest, the dominant permeability is to potassium, so the membrane potential is close to ek. ) Axons propagate information from one region of the nervous system to another, by brief electrical impulses called action potentials. Action potentials usually start at the initial segment of the axon and then propagate down the length of the axon to the presynaptic terminals. The action potential is a transient depolarizing spike that moves down the axon. At the action potential peak, the membrane potential approaches ena. The threshold is determined by the properties of ion channels in the axon membrane, especially a class of channels called voltage-gated sodium channels: once the action potential starts, it keeps going.