The vector represents the electrical activity of the myocardium. How Cardiac Vectors Represents the Electrical Activity of the Myocardium? The wave of depolarization moving from the negative pole to the positive pole produces electromagnetic force represented by a vector When myocardial cells are stimulated, the voltage goes towards THP cells are depolarized and become electrically positive. Ii) When there is no electrical activity in the myocardial cells, the needle of the galvanometer will remain at a neutral position or at zero position. I) When there is electrical activity in the myocardial cells, the needle of the galvanometer will fluctuate The function of the galvanometer is to detect the electrical activity in any object where its electrode is placed Galvanometer has positive and negative electrodes. How ECG Interpretation Machine (Galvanometer) Records Electrical Activity of the Heart? Galvanometer – Introduction, and FunctionsĮCG machine works on the principle of a galvanometer. Ii) In SA/AV nodal cells, Ca influx causes depolarization. I) In atrial/ventricular myocardial cells, Na influx cause depolarization This fluctuation of electrical potentials in the membrane is called the Action potential. Then, the voltage-gated Ca and K-channels open simultaneously for a short time, eventually, Ca-channels are closed but K-channels keep on opened, taking the membrane potential to its resting potential, this is called repolarization of a membrane Thus, depolarization of one cell leads to the depolarization of the second cell and the second cell is responsible for the depolarization of the third cell and so on. The cations (Na) from the first stimulated cell trickle into the next cell through these gap junctions, taking the voltage of the next cell towards the THP, then opening of the voltage-gated Na-channels results in depolarization of the membrane. These are very special connections between the adjacent myocardial cells, and also called electrical windows. Gap Junction (Electrical Windows) Between Adjacent Myocardial Cells ECG interpretation can be fun if you have clear concepts. Due to heavy K-efflux, K is progressively lost until membrane potential becomes -90mV and now membrane is repolarized. As there is no voltage difference, we can say the electrical potential is showing the Plateau phase.Īfter some time, Ca channels close and K-channels become more and more active. So for a very short time, K keeps on moving out and Ca keeps on moving in, this loss and gain of the cations, no net change occurs in potential. When a cell starts losing cations (K), voltage comes toward electronegativity but as soon as it becomes zero, Ca-channels also open. K starts rushes outside because intracellular K is normally more as compared to extracellular K. i.e., Ca and K-channels, both are activated. Now we can say that membrane lost its negative polarity and depolarized.Īfter depolarization of the cell, depolarization sensitive channels. This membrane potential is progressively going to positive value e.g.: +10mV. THP will become -60mV then -50mV, -40mV, and eventually becomes 0mV. As soon as it touches THP, the voltage-gated Na-channel opens and lots of Na comes in and progressively neutralizes 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. Threshold Potential – Definition and How to Determine THP As 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. 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. When the myocardial cell is not stimulated, it is in a state of resting membrane potential (RMP). Resting membrane potential (RMP) is the electrical voltage difference between the inside and outside of the membrane. The Function of Electrical Activity in Ventricular Myocardium The graphical representation of the electrical activity of the heart is called electrocardiography. Master Medical Sciences with crystal clear concepts. Not a member? Sign up now to access 800+ videos on Basic Medical Sciences & Clinical Medicine. ECG Interpretation World’s Most Popular Lecture on EKG Interpretation
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