Electrical Signals in Neurons (Cont’d)

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Electrical Signals in Neurons (Cont’d)

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 5 Current Lecture  Recording from Single K+ Channels o Measure current going through ion channels o Current  Movement of charge  Ions carry charge as they move through solution (carry current) o Take a glass pipette with very small tip and press against the membrane of a neuron, the binding of the glass and those of the membrane become tight  If there is an ion channel and the seal between the membrane and the glass is tight then the current will flow into the electrode amplifier  Small current of 10 pA appears rapidly and shuts of  Current turns on and of very fast  Measures the opening and closing of the ion channels (turning on and shutting of current)  Time at which a channel opens is random, but you can measure the probability of whether or not it will be open  Directly demonstrates that this channel is voltage gated  Depolarization affects single channel currents o Increase in probability of opening  Depolarize the membrane  Channels open more frequently (still random but probability higher) o Increase in amplitude of current  When depolarize you can increase the amplitude o Ohm’s Law: I=V/R  Current = movement of charge (ions)  Voltage= the force causing the charge  Resistance= the property of material that impedes current flow (membrane)- lipid bilayer has very high resistance o For Single Channel Currents: i=[V(m)-E(ion)]/R

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