The cardiac cycle

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Cards (17)

  • Heart beats by contraction and relaxation of cardiac muscle
  • It’s co ordinated by electrical activity and accompanied by heart sounds - from the valves in heart closing
  • One complete relaxation and contraction is one heartbeat
  • Valves open when pressure in front of them is greater - forces valve open
  • When pressure after valve exceeds pressure before it - pushing or blood towards valve closes it
  • Valves on open in one direction - blood flow unidirectional
  • Contraction of atria using atrial muscle called atrial systole
    contraction of ventricles using ventricular muscles called ventricular systole
  • relaxation of the heart muscle called diastole
  • Diastole
    • heart relaxed
    • AV valves open - atria and then ventricles fill up with blood
    • SL valves closed to prevent back flow of blood from previous beat
  • Atrial systole
    • begins at right atrium - quickly spreads to left to co ordinate heartbeat
    • atria contract - squeeze blood into ventricles
    • muscles close at top of veins preventing back flow
  • Ventricular systole
    • ventricles contract and squeeze blood through arteries - SL valves open and AV valves closed
  • Cardiac output = stroke volume x heart rate
  • During exercise
    • body needs more oxygen and glucose for increased respiration to increase release of energy for muscle contraction
    • heart rate will increase
  • With time cardiac muscle become stronger and contract harder which increases the stroke volume - same cardiac output but lower heart rate