HHP 3500 Lecture Notes - Lecture 10: Potassium Channel, Axon Terminal, Schwann Cell

• School: University of Iowa
• Department: Health and Human Physiology
• Course: HHP 3500
• Professor: Peterson Clayton

Document Summary

Ability of an excitable membrane (neuronal axons, muscle fiber membranes) to propagate action potentials is dependent upon voltage gated ion channels. 2 voltage gated channels: open as soon as we reach a voltage threshold (about 15 mv above resting, so -55mv) Potassium: proteins that make up potassium channel change shape slowly, so they open and close very slowly. Axon diameter-bigger axon, the less resistant to current flow, then the faster the current will flow. Myelination-comes from glial cells- (cns= oligodendricites; pns= schwann cells); prevents ion leakage; the wrapping allows it to flow much further before it can stimulate another action potential: refractory periods. Absolute refractory period-you cannot fire another action potential because the sodium gated channels are inactivated, until the potential depolarizes. Relative refractory period-beginning of repolarizes to the end of after hyperpolarizes; you can fire another action potential, but the stimulus will need to be much greater; because its working against potassium efflux.