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Lecture 3

Lecture 3 on Neurons

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Biological Sciences
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BIOB30Fall2011 Chapter 8 Neurons Cellular and Network PropertiesLecture 3 Voltage Gated Channels o Opening and closing of voltage gated ion channels causes changes in membrane permeability allows movement of ions between IC and ECleads to changes in excitability of the cell the cell can change its membrane potentialmuscle and nerve cells o The membrane potential differenceVm in relation to 0 o Towards 0depolarisation Vm becomes less negative o More negative than RMPhyperpolarisation o Towards RMP when depolarisedrepolarisation o RMPdepolarisationrepolarisationhyperpolarizationRMP o Depolarization excitation is mainly caused by the opening of Na channels o The Na channels have 2 gatesonly one can be closed at any given time but they open and close very quickly o They can only be activated when the activation gate is closedthey are activated when the Vm is 55mV or less negative o They cannot be activated when the inactivation gate is closed o The Na ions only flow into the cell when BOTH gates are open o At RMP activation gate is closed and inactivation gate is open causing no Na flux o Depolarisation activation gate opens inactivation gate stays open and Na flows into the cell55mV o After 05 ms inactivaction gate closes preventing any more Na flux o After another 05ms the gates reset to default the inactivation gate opens and remains open while the activation gate closes o There are 2 types of K channels leak channels and voltage gated K channels o Leak channelsusually open open at RMP contribute to the 70 mV resting potential
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