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Heart Physiology

Heart Physiology. What a Job!. It pushes your six liters of blood through your blood vessels over 1000 times a day! Thousands of cells function as one unit!. Basic Heart Anatomy. Note: Right & left are named based on position in the chest & seem reversed in a diagram

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Heart Physiology

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  1. Heart Physiology

  2. What a Job! • It pushes your six liters of blood through your blood vessels over 1000 times a day! • Thousands of cells function as one unit!

  3. Basic Heart Anatomy Note: Right & left are named based on position in the chest & seem reversed in a diagram • Superior chambers = atria • Small, limited muscle • Inferior chambers = ventricles • Large, heavily muscled • Pumping chambers • Septum divides ventricles

  4. Valves • Prevent back-flow of blood • Two atrioventricular (AV) valves: • Tricuspid • Bicuspid/mitral • Two semilunar valves: • Pulmonary • Aortic

  5. Purpose? • Pulmonary circuit • Between heart & lungs Why? What is the pump? • Systemic circuit • Between heart & rest of body Why? What is the pump?

  6. Right Atrium • Receives deoxygenated blood from • Superior vena cava (from body above diaphragm) • Inferior vena cava (from body below diaphragm) • Coronary sinus (from heart) • Passes blood through tricuspid valve to RV

  7. Left Atrium • Receives oxygenated blood from lungs through: • Right and left superior pulmonary veins • Right and left inferior pulmonary veins • Passes blood through the bicuspid/mitral valve to the LV

  8. Ventricles • RV pumps deoxygenated blood to lungs through pulmonary semilunar valveinto pulmonary trunk • LV pumps oxygenated blood to body through aortic semilunar valveto aorta

  9. Cardiac Cycle = one heartbeat • Systole – contraction of the ventricles • Diastole – relaxation of the ventricles • Events occur in 3 phases:

  10. 1: Mid-to-Late Diastole • Heart in complete relaxation • Low pressure • Blood flowing into atria and ventricles • Semi-lunar valves closed • A-V valves open END – atria contract and force remaining blood into ventricles

  11. 2: Ventricular Systole • Ventricles contract, increasing pressure • A-V valves close • Atria begin filling with blood END – • Ventricular pressure > artery pressure • Blood forced out semilunar valves

  12. 3. Early Diastole • Ventricles relax, dropping pressure • Semi-lunar valves close END – • Atrial pressure > ventricular pressure • Blood is forced through AV valves

  13. Heart Rhythm • Intrinsic Conduction System (ICS) – “specialized” tissue sets basic rhythm, ~75 beats/minute • Extrinsic Control – nervous system can increase or decrease heart rate

  14. Intrinsic Conduction System Starts with autorhythmic cells: • SA (sinoatrial) Node – “Pacemaker” - causes the atria to contract • AV (atrioventricular) Node – causes ventricles to contract Continues through rest of ICS: • Bundle of His • Bundle branches • Purkinje fibers

  15. Depolarization Sequence 1 2

  16. 3 4 5

  17. Electrocardiogram [ECG] • Traces the flow of current through the heart

  18. Cardiac Output • Stroke Volume (SV) – Blood pumped per ventricle per heartbeat • Cardiac Output (CO) – Blood pumped per ventricle per minute = Heart Rate (HR) * Stroke Volume (SV) Normal Adult HR is ~75 beats/minute Average resting SV is ~70 ml/beat What is the average adult CO?

  19. Irregular Heartbeats • Tachycardia • (>100 beats/min) • Bradycardia • (<60 beats/min) • Ischemia – lack of adequate blood supply • Fibrillation– rapid uncoordinated shuddering of heart muscle (major cause of heart attack/death)

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