Resting membrane potential (RMP) is the electrical voltage difference between the inside and outside of the membrane. When the myocardial cell is not stimulated, it is in a state of resting membrane potential (RMP). Normally, resting ventricular myocardial cells are electrically negative inside.įor example the RMP of the ventricular myocardial cell is -90mV, which means that in the resting condition, the myocardial cell internally has a negatively polarized membrane. Threshold Potential – Definition and How to Determine THPĪs soon as the myocardial cell is stimulated, some cations will move into to the cells, this positively charged ions moving into the cells will take RMP towards the less negative state, because cations will neutralize the electronegativity. Thresh hold potential (THP) is a potential at which voltage-gated Na-channels in the membrane suddenly open, while in RMP that voltage-gated Na-channels were closed.Īfter stimulation to the cell, the voltage starts moving towards Thresh hold potential (THP) which is -70mV in the ventricular myocardial cell. As soon as it touches THP, the voltage-gated Na-channel opens and lots of Na comes in and progressively neutralizes the electronegativity. THP will become -60mV then -50mV, -40mV, and eventually becomes 0mV. This membrane potential is progressively going to positive value e.g.: +10mV. Now we can say that membrane lost its negative polarity and depolarized.Īfter depolarization of the cell, depolarization sensitive channels.
i.e., Ca and K-channels, both are activated. K starts rushes outside because intracellular K is normally more as compared to extracellular K.
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