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Impulse Conduction through the heart

Impulse Conduction through the heart - Calcium Ion and...

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Impulse Conduction through the heart •SA node begins the action potential •Stimulus spreads to the AV node •Impulse is delayed at AV node •Impulse then travels through ventricular conducting cells •Then distributed by Purkinje fibers The electrocardiogram (ECG) •A recording of the electrical events occurring during the cardiac cycle •The P wave accompanies the depolarization of the ventricles •The QRS complex appears as the ventricles depolarize •The T wave indicates ventricular repolarization Contractile Cells •Resting membrane potential of approximately –90mV •Action potential •Rapid depolarization •A plateau phase unique to cardiac muscle •Repolarization •Refractory period follows the action potential
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Unformatted text preview: Calcium Ion and Cardiac contraction •Cardiac action potentials cause an increase in Ca 2+ around myofibrils •Ca 2+ enters the cell membranes during the plateau phase •Additional Ca 2+ is released from reserves in the sarcoplasmic reticulum The cardiac cycle •The period between the start of one heartbeat and the beginning of the next •During a cardiac cycle •Each heart chamber goes through systole and diastole •Correct pressure relationships are dependent on careful timing of contractions Pressure and volume changes: atrial systole •rising atrial pressure pushes blood into the ventricle •atrial systole •the end-diastolic volume (EDV) of blood is in the ventricles...
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