Heart physiology

1. Heart Physiology (pg 6)

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. 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. 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. Components of the Conduction System 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. Components of the Conduction System 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 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. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles

8. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles 4. Right and left bundle branches: extend down the sides of the interventricular septum. Branch profusely to form the conduction myofibers

9. 3. AV bundle (bundle of His): Conducts impulses from atria to ventricles 4. Right and left bundle branches: extend down the sides of the interventricular septum. Branch profusely to form the conduction myofibers 5. Conduction myofibers (Purkinje fibers): Transmit impulses throughout the ventricular myocardium so that both ventricles contract at the same time

10. Conduction system diagram (pg 7) Color code

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. 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. 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. Cardiac cycle Systole = contraction phase Diastole = relaxation phase

15. Cardiac Output Volume of blood pumped by a ventricle in 1 minute

16. Cardiac Output Volume of blood pumped by a ventricle in 1 minute = Stroke volume (ml/cycle) x Heart Rate (cycles/minute)

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 CO 2 , low pH, high temperature, emotions (fear, anxiety, excitement, anger)