106 Depolarization (phase 0) of cardiac pacemaker cells is slower than that of ventricular myocytes and depends on which of the following ion movements? A) Caefflux 1 B) Ca influx C) Na efflux D) Na influx E) K-efflux F) K-influx
Electrochemical potential gradient across the cellular membrane enables the cardiac cells to propagate action potential. Sodium (Na+), potassium (K+), and calcium (Ca2+) ions are present in different concentrations inside the cells compared to their surrounding environment. Concentration of Sodium and calcium are more in the extracellular environment whereas potassium is present at a higher concentration inside the cell. The Voltage-sensitive ion channels present on the cellular membranes facilitates the movement of these ions. The tendency of these ions to move down their chemical gradient and the tendency for charges to balance out across membranes contributes to a net electrochemical potential that differs with the status of ion channels called phases. Cycles of such phases starts when the cell membranes attains a threshold potential which is different for cardiomyocytes and pacemaker cells.
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