Untitled Flashcards Set

  1. Atrial Contraction:

    • Atrial pressure > ventricular pressure → blood flows into ventricles.

    • Associated with P wave (atrial depolarization).

  2. Isovolumetric Contraction:

    • Ventricular pressure rises but no blood ejection (mitral and aortic valves closed).

    • Critical for building pressure to overcome aortic pressure.

    • Preceded by QRS complex (ventricular depolarization).

  3. Ejection Phase:

    • Ventricular pressure > aortic pressure → aortic valve opens, and blood is ejected.

    • Aortic valve closes at the end of this phase to prevent backflow.

  4. Isovolumetric Relaxation:

    • Ventricles relax, ventricular pressure drops, but all valves remain closed.

    • Allows pressure to equalize for next cycle.

  5. Rapid Filling:

    • Mitral valve opens → rapid ventricular filling from atria due to pressure gradient.

    • Ends as atrial pressure gradient decreases.

ECG and Mechanical Events

  • P wave: Atrial depolarization → atrial contraction.

  • QRS Complex: Ventricular depolarization → start of systole.

  • T wave: Ventricular repolarization → relaxation (diastole).

Heart Sounds and Valve Function

  • "Lub" (First Sound): Closure of mitral and tricuspid valves during isovolumetric contraction.

  • "Dub" (Second Sound): Closure of aortic and pulmonary valves during isovolumetric relaxation.

Pressure Dynamics

  • Pressure differences dictate valve opening and closure:

    • Mitral valve closes: Ventricular pressure > atrial pressure.

    • Aortic valve opens: Ventricular pressure > aortic pressure.