Final answer:
The resting membrane potential for cardiocytes is approximately -80 mV for atrial cells and -90 mV for ventricular cells, and these cations, like sodium and calcium, flow through gap junctions between cells.
Step-by-step explanation:
At a resting membrane potential of approximately -80 mV for atrial cells and -90 mV for ventricular cells, cardiocytes receive cations diffusing from adjacent cardiocytes through gap junctions. The resting membrane potential is a state of relative electrical charge across the cell's membrane and is essential for the physiological response to chemical or other signals. Contractile cardiocytes have a more stable resting phase compared to conductive cardiocytes that exhibit autorhythmicity, causing the membrane potential to fluctuate with regular depolarizations due to the slow influx of Na+ and Ca2+ ions.
Movement of ions across their concentration gradients and through protein channels in the cell membrane creates this electrical potential. When Na+ channels open, the higher concentration of Na+ outside the cell compared to the inside causes an influx, depolarizing the cell. This leads to the action potentials necessary for heart muscle contraction and proper cardiac function.