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  2. 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.

  3. Cardiac excitation-contraction coupling - Wikipedia

    en.wikipedia.org/wiki/Cardiac_excitation...

    This rate can be altered, however, by nerves that work to either increase heart rate (sympathetic nerves) or decrease it (parasympathetic nerves), as the body's oxygen demands change. Ultimately, muscle contraction revolves around a charged atom (ion) , calcium (Ca 2+ ) , [ 3 ] which is responsible for converting the electrical energy of the ...

  4. Heart rate - Wikipedia

    en.wikipedia.org/wiki/Heart_rate

    Those patients whose heart rate was above 70 beats per minute had significantly higher incidence of heart attacks, hospital admissions and the need for surgery. Higher heart rate is thought to be correlated with an increase in heart attack and about a 46 percent increase in hospitalizations for non-fatal or fatal heart attack. [73]

  5. What Is Heart Disease? Everything You Need to Know - AOL

    www.aol.com/heart-disease-everything-know...

    Heart arrhythmias refer to problems involving the heart rate or heart rhythm that result from abnormal electrical activity in the heart. Arrhythmias can cause your heart to beat too rapidly ...

  6. Does your heart beat faster when you stand or sit up? Learn ...

    www.aol.com/does-heart-beat-faster-stand...

    POTS patients experience an increase in heart rate within a few minutes of standing or sitting up. This makes it different from other conditions that generally cause a fast heart rate.

  7. “Why Did My Period Come Early?” Here Are 7 Reasons for ...

    www.aol.com/why-did-period-come-early-140000540.html

    There’s nothing more annoying than being caught unawares by Aunt Flo—so when your body and your period tracker aren’t in agreement and bleeding happens sooner than expected, it’s only ...

  8. Effective refractory period - Wikipedia

    en.wikipedia.org/wiki/Effective_refractory_period

    This period is approximately equal to the absolute refractory period (ARP), it occurs because the fast sodium channels remain closed until the cell fully repolarizes. [1] During this period, depolarization on adjacent cardiac muscles does not produce a new depolarization in the current cell as it has to refract back to phase 4 of the action ...

  9. Cardiac physiology - Wikipedia

    en.wikipedia.org/wiki/Cardiac_physiology

    Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.