Heart physiology

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Heart physiology

  1. 1. Heart Physiology (pg 6)
  2. 2. Conduction System• To pump blood efficiently, both atria need to contract at the same time, followed by contraction of both ventricles (the cardiac cycle)
  3. 3. Conduction System• To pump blood efficiently, both atria need to contract at the same time, followed by contraction of both ventricles (the cardiac cycle)• Contraction is coordinated by the conduction system, which carries the signal to contract throughout the heart
  4. 4. Conduction System• To pump blood efficiently, both atria need to contract at the same time, followed by contraction of both ventricles (the cardiac cycle)• Contraction is coordinated by the conduction system, which carries the signal to contract throughout the heart• Intercalated disks allow signal to travel rapidly between adjacent cells
  5. 5. Components of the Conduction System1. Sinoatrial node: located on the posterior wall of the right atrium, near the entrance of the superior vena cava. Initiates impulses 70-80 times per minute. Pacemaker of the heart. Impulses travel rapidly throughout the atrial myocardium and cause the two atria to contract simultaneously
  6. 6. Components of the Conduction System1. Sinoatrial node: located on the posterior wall of the right atrium, near the entrance of the superior vena cava. Initiates impulses 70-80 times per minute. Pacemaker of the heart. Impulses travel rapidly throughout the atrial myocardium and cause the two atria to contract simultaneously2. Atrioventricular (AV) node: Located on the floor of the right atrium. Cells in the AV node conduct impulses slowly. This allows time for the atria to finish contracting before the ventricles begin contracting
  7. 7. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles
  8. 8. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles4. Right and left bundle branches: extend down the sides of the interventricular septum. Branch profusely to form the conduction myofibers
  9. 9. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles4. Right and left bundle branches: extend down the sides of the interventricular septum. Branch profusely to form the conduction myofibers5. Conduction myofibers (Purkinje fibers): Transmit impulses throughout the ventricular myocardium so that both ventricles contract at the same time
  10. 10. Conduction system diagram (pg 7)• Color code
  11. 11. Electrocardiograms (ECG or EKG)• Impulses conducted through the heart during a cardiac cycle produce electric currents that can be measured on the surface of the body to produce an electrocardiogram
  12. 12. Electrocardiograms (ECG or EKG)• Impulses conducted through the heart during a cardiac cycle produce electric currents that can be measured on the surface of the body to produce an electrocardiogram• Diagram
  13. 13. Electrocardiograms (ECG or EKG)• Impulses conducted through the heart during a cardiac cycle produce electric currents that can be measured on the surface of the body to produce an electrocardiogram• Diagram• Useful in evaluating heart function. For example, a heightened p wave indicates an enlarged atrium
  14. 14. Cardiac cycle• Systole = contraction phase• Diastole = relaxation phase
  15. 15. Cardiac Output• Volume of blood pumped by a ventricle in 1 minute
  16. 16. Cardiac Output• Volume of blood pumped by a ventricle in 1 minute• = Stroke volume (ml/cycle) x Heart Rate (cycles/minute)
  17. 17. Cardiac Output• Volume of blood pumped by a ventricle in 1 minute• = Stroke volume (ml/cycle) x Heart Rate (cycles/minute)• Heart rate: SA node sets basic rate, but it can be changed by the cardiac center in the medulla oblongata. Rate increases in response to epinephrine, low blood pressure, high CO2, low pH, high temperature, emotions (fear, anxiety, excitement, anger)

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