Chapter 7 Notes - Chapter 7: Nerve Cells and Electrical...

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Chapter 7: Nerve Cells and Electrical Signalling October, 2007 Establishment of the Resting Membrane Potential -cell is at rest usually -70 mV - this means that the inside of the typical neuron at rest is 70 mV more negative compared to the outside - all cells in the body have negative membrane potential ranging from -5 mV to -100 mV Determining the Equilibrium Potentials for Potassium and Sodium Ions - resting membrane potential depends on two critical factors: 1) concentration gradients of ions (especially sodium and potassium) 2) presence of ion channels in the plasma membrane Membrane Potential of a Cell Permeable only to Potassium - see Figure 7.6 Membrane Potential of a Cell Permeable Only to Sodium - see figure 7.7 Resting Membrane Potential of Neurons - number of open potassium channels far exceeds the number of open sodium channels thus membrane is 25 times more permeable to potassium than sodium -see figure 7.8 Neurons at Rest - membrane potential usually affected by 2 or more ions – each tries to bring membrane potential closer to the equilibrium potential - the net electrochemical force on an ion tends to move that ion across membrane in the direction that will move the membrane potential toward that ion’s equilibrium potential i.e. bring the ion closer to equilibrium Electrical Signaling Through Changes in Membrane Potential - gated channels open or close in response to particular stimuli which changes membrane potential i.e. changes the membrane permeability for that specific ion - three types of gated ion channels: 1) voltage-gated channels 2)ligand-gated channels 3) mechanically gated channels - mechanically gated channels open or close in response to mechanical force on the membrane Describing Changes in Membrane Potential - see figure 7.9 (hyperpolarization, depolarization, repolarization) - neurons communicate via two different types of electrical signals that result from opening or closing of gated ion channels 1) graded potentials 2)action potentials Graded Potentials - small changes in membrane potential that happen when ion channels open or close in response to a stimulus acting on the cell -
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This note was uploaded on 04/20/2008 for the course PHL psl201 taught by Professor Bandali during the Spring '08 term at University of Toronto- Toronto.

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Chapter 7 Notes - Chapter 7: Nerve Cells and Electrical...

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