KINE 1P90 Lecture Notes - Lecture 8: Pacemaker Potential, Membrane Potential, Resting Potential
4 Nov 2016
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Document Summary
Cardiac muscle generates its own electrical signal: autoconduction. 1% of cardiac muscle cells are specialized and spontaneously initiate contraction. Contractile cells are 99% of the cardiac muscle cells and do the mechanical work. Authorythmic cells are 1% of the cardiac muscle cells; they initiate and conduct action potentials. Autorythmic cells do not have a resting potential but rather they have a pacemaker potential always happening, causes the pace of the heartbeat. Their membrane potential depolarizes slowly, or drifts, until threshold is reached and action potential results. This drift and the resulting action potential occurs in repeating cycles. The action potentials spread throughout the heart and trigger its repetitive beating. Unlike other cells with a resting potential, cells with a pacemaker potential have an electric difference across the membrane that is constantly changing by itself. The electric charge across the cell membrane is sonctantly changing due to the movement of k+, na+, and ca++ ions across the membrane.
