PHYS 215 Lecture Notes - Lecture 4: Myelin, Cardiac Muscle, Axon Terminal

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1. Neurophysiology
Excitable tissues
oNerves and muscles
oMembrane potential = Vm (membrane voltage)
oIntracellular recording
Measurement of ion changes across the cell membrane
3 phases to the action potential
Phase 1: Depolarization
ocell becomes more positive inside
Phase 2: repolarization
oCell returns to the resting membrane potential
Phase 3: hyperpolarization
oCell becomes more negative inside than the
resting membrane
What happens to the neuron?
oCell receives signals from synapsing neurons
oSignals have to add up enough to reach threshold
Graded potentials – local changes in membrane potential
oSignals that don’t reach the threshold are termed
“subthreshold”
oAt threshold, signal is passed on by depolarizing the neighboring
membrane
o3 phases are due to the changes in permeability to Na+ and K+
ions
Action potential channel currents
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