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

7. Purpose?  Pulmonary circuit  Between heart & lungs Why? What is the pump?  Systemic circuit  Between heart & rest of body Why? What is the pump?

8. 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

9. 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

10. Ventricles  RV pumps deoxygenated blood to lungs through pulmonary semilunar valve into pulmonary trunk  LV pumps oxygenated blood to body through aortic semilunar valve to aorta

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

12. 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 END – atria contract and force remaining blood into ventricles

13. 2: Ventricular Systole  Ventricles contract, increasing pressure  A-V valves close  Atria begin filling with blood END END –  Ventricular pressure > artery pressure  Blood forced out semilunar valves

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

15. Heart Rhythm 1. Intrinsic Conduction System (ICS) – “specialized” tissue sets basic rhythm, ~75 beats/minute 2. Extrinsic Control – nervous system can increase or decrease heart rate

16. Intrinsic Conduction System Starts with autorhythmic cells: 1. SA (sinoatrial) Node – “Pacemaker” - causes the atria to contract 2. AV (atrioventricular) Node – causes ventricles to contract Continues through rest of ICS: 3. Bundle of His 4. Bundle branches 5. Purkinje fibers

18. Depolarization Sequence 1 2

19. 43 5

20. Electrocardiogram [ECG/EKG]  Traces the flow of current through the heart

21. 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?

22. 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)