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  2. Cardiac physiology - Wikipedia

    en.wikipedia.org/wiki/Cardiac_physiology

    The first heart sound S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The second heart sound, S2, is the sound of the semilunar valves closing during ventricular diastole and is described as "dub". [1]

  3. T wave - Wikipedia

    en.wikipedia.org/wiki/T_wave

    Repolarization of the ventricle happens in the opposite direction of depolarization and is negative current, signifying the relaxation of the cardiac muscle of the ventricles. But this negative flow causes a positive T wave; although the cell becomes more negatively charged, the net effect is in the positive direction, and the ECG reports this ...

  4. Heart sounds - Wikipedia

    en.wikipedia.org/wiki/Heart_sounds

    The first heart sound, or S 1, forms the "lub" of "lub-dub" and is composed of components M 1 (mitral valve closure) and T 1 (tricuspid valve closure). Normally M 1 precedes T 1 slightly. It is caused by the closure of the atrioventricular valves , i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole .

  5. Cardiac cycle - Wikipedia

    en.wikipedia.org/wiki/Cardiac_cycle

    In a healthy heart all activities and rests during each individual cardiac cycle, or heartbeat, are initiated and orchestrated by signals of the heart's electrical conduction system, which is the "wiring" of the heart that carries electrical impulses throughout the body of cardiomyocytes, the specialized muscle cells of the heart.

  6. Heart - Wikipedia

    en.wikipedia.org/wiki/Heart

    The first heart sound S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The second heart sound, S2, is the sound of the semilunar valves closing during ventricular diastole and is described as "dub". [8]

  7. Systole - Wikipedia

    en.wikipedia.org/wiki/Systole

    Electrical waves track a systole (a contraction) of the heart. The end-point of the P wave depolarization is the start-point of the atrial stage of systole. The ventricular stage of systole begins at the R peak of the QRS wave complex; the T wave indicates the end of ventricular contraction, after which ventricular relaxation (ventricular diastole) begins.

  8. Sinoatrial node - Wikipedia

    en.wikipedia.org/wiki/Sinoatrial_node

    Sinus node dysfunction also known as sick sinus syndrome is a group of irregular heartbeat conditions caused by faulty electrical signals of the heart. When the heart's sinoatrial node is defective, the heart's rhythms become abnormal—typically too slow or exhibiting pauses in its function or a combination, and very rarely faster than normal ...

  9. Cardiac action potential - Wikipedia

    en.wikipedia.org/wiki/Cardiac_action_potential

    When this happens, the voltage within the cell increases slightly. If this increased voltage reaches the threshold potential (approximately −70 mV) it causes the Na + channels to open. This produces a larger influx of sodium into the cell, rapidly increasing the voltage further to around +50 mV, [ 6 ] i.e. towards the Na + equilibrium potential.