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Heart Conduction & Cardiac Cycle

Heart Conduction & Cardiac Cycle. Cardiac Circulation. Myocardium nourished by coronary artery Coronary veins drain into coronary sinus (enlarged vessel on backside of heart) Coronary sinus empties into right atrium. Heart Conduction.

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Heart Conduction & Cardiac Cycle

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  1. Heart Conduction & Cardiac Cycle

  2. Cardiac Circulation • Myocardium nourished by coronary artery • Coronary veins drain into coronary sinus (enlarged vessel on backside of heart) • Coronary sinus empties into right atrium

  3. Heart Conduction • Cardiac muscle does not have to be controlled by nervous system • Muscle cells in different areas of heart have different rhythms

  4. Heart Rate influences • Autonomic nervous system increases & decreases heart rate • Intrinsic conduction system (nodal system) causes heart muscle depolarization (electric impulse that causes heart beat)

  5. Heart Beat • SA node (also known as pacemaker) • Located in right atrium • Starts heart beat • Impulse travels through atrium to the AV node • Atrium contract

  6. Impulse through AV bundle through bundle branches to Purkinje fibers in apex • Ventricle contracts starting at apex and moving toward the atria. • Blood forced upward out of the aorta

  7. Cardiac Cycle = complete heart beat • Atria contract simultaneously • Atria relax • Ventricles contract • Systole = contraction of ventricle • Diastole = relaxation of ventricle

  8. Mid to late diastole • Ventricle completely relaxed • Pressure low in heart • Blood flowing passively into and through atria into ventricles • Semilunar valves closed, AV valves open • Then atria contract, forcing blood into ventricles

  9. 2. Ventricular systole • Ventricles contract (atria relax-filling with blood) • Pressure increases, closing AV valves (lub sound) • Higher pressure in ventricles, than in arteries so forces semilunar valves open and blood is forced into arteries

  10. 3. Early diastole • Ventricles relax • Semilunar valves close (preventing back flow) • Dup sound • Intraventicular pressure drops, until low enough for AV valves to be forced open

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