BMS 300 1st Edition Lecture 19 Outline of Last Lecture I. Cells of the nervous system -Glia -Glia 1. maintain the environment for neural function -Glia cells in the nervous system1. astrocytes >regulation of extracellular environment2. oligodendrocytes >lay down myelin sheaths/wraps 3. Glia of the peripheral nervous system >Schwann cells II. Neurons as electrically excitable cells -storing energy in an electrical gradient1. the potassium battery >role of K+ selective leak channels >role of impermanent anions2. the nervous potential >role of the [ko]/[ki] ration III. The Na+ channel of switching polarity These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1. the gate 2. inactivation 3. voltage/charge sensitivity Outline of Current Lecture IV. Membrane potential to action potential and propagation-role of K+, A-, & K+ leak channels in Restin’s membrane potential -role of Na+ channels to switch polarity -concept of ion permeability 1. membrane potential seeks the equilibrium potential of the ion whose permeability is dominant V. The Action Potential -sequential openings and closing of ion channels 1. V-gated Na2. V-gated K+ VI. Na+ channel properties -voltage/charge sensitive -inactivates-closes VII. Propagating potentials -in membrane lacking v-gated channels -unmyelinated conductile regions -myelinated conductile regionsCurrent LectureStarting with the image we started last lecture: -we reach equilibrium because of the electro charge -using the equation we talked about last lecture -Ek=70-80mv -the resting membrane potential was almost the same as Ek -potassium battery -2 forces that are trying to bring sodium is the concentration and electrical gradient -which means Na can’t come into the cells because the channels are gated -when the gate swings open the positive charge comes in and then the ball and chain block the gates **the membrane potential seeks the equilibrium potential of the ion whose permeability is dominant -if we graph it we can see how it affects the membrane potential Threshold: the point where Na+ influx is balanced by K+ efflux aka the point where Na permeability is balanced by K+ permeability-the Na channel closes (inactivates) shortly after opening -action potential happens extremely fast Relating changes in voltage and permeability in an action potential -forms a cycle that can all occur very fast -the # of ions that move is really
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