PHYS 215 Lecture Notes - Lecture 4: Myelin, Cardiac Muscle, Axon Terminal
12 Sep 2016
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Excitable tissues: nerves and muscles, membrane potential = vm (membrane voltage, intracellular recording. Measurement of ion changes across the cell membrane. Phase 1: depolarization: cell becomes more positive inside. Phase 2: repolarization: cell returns to the resting membrane potential. Phase 3: hyperpolarization: cell becomes more negative inside than the resting membrane. What happens to the neuron: cell receives signals from synapsing neurons, signals have to add up enough to reach threshold. Graded potentials local changes in membrane potential: signals that don"t reach the threshold are termed. Subthreshold : at threshold, signal is passed on by depolarizing the neighboring membrane, 3 phases are due to the changes in permeability to na+ and k+ ions. Na+/k+ atpase: the sodium/ potassium pump restores the resting concentration of sodium and potassium ions, 3 na+ out for 2 k+ in, voltage gated sodium channels. Excitability in neuronal tissue, skeletal muscle, and cardiac muscle. At rest all na+ channels are closed (vm= -70mv)
