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→What does the ECG register?
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=What does the ECG register?= | =What does the ECG register?= | ||
An ECG is a registration of the heart's electric activity. | An ECG is a registration of the heart's electric activity. | ||
Just like skeletal muscles, the heart is electrically stimulated to contract. This stimulation is also called ''activation'' or ''excitation''. Cardiac muscles are electrically charged | Just like skeletal muscles, the heart is electrically stimulated to contract. This stimulation is also called ''activation'' or ''excitation''. Cardiac muscles are electrically charged at rest. The surface of the cell is positively charged relative to the inside (resting potential). If the cardiac muscle cells are electrically stimulated they depolarize (the outside of the depolarized region is positively charged relative to the inside) and contract. | ||
As the impulse spreads through the heart, the electric field changes continually in size and direction. The ECG is a graphical visualisation of the electric signals in the heart. | |||
=The ECG is a sum of the action potentials from millions of cardiomyocytes= | =The ECG is a sum of the action potentials from millions of cardiomyocytes= | ||