CJH332H1 Study Guide - Midterm Guide: Electric Current, Saltatory Conduction, Immunofluorescence
Document Summary
Cjh332 lecture 7 myelin, aps, transmitting messages. Na inactivation means channel cannot be re-opened with depolarization. Na flowing in depolarizes on both sides, no inherent direction of flow. Na channel inactivation (absolute refractory period) prevents backward flow of ions/depolarization/ap. Insert electrode and inject positive charge to depolarize. If below threshold, current will flow and dissipate. Electrophysiology: measure potential on either side of axon where ions injected. Inject current, measure how quickly initial charge dissipates. Length constant ( ) = distance where voltage is 1/e (37%) of initial voltage. High r-membrane means currents can spread farther before ions are leaked through the membrane. Longer length constant is better for electrical signals. Bigger axon allows more space for ions to flow (less interaction with other positive charges in axon: decreasing the leakiness (increasing r-membrane) More ions stay inside while flowing (less leak), more flow. Core of axon has low ion conductance b/c of internal resistance due to other positive charges.
