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  1. 1. The Cardiovascular System
  2. 2. Heart Beat <ul><li>Electrical impulse carried from parts of the brain to the heart from the vagus nerve </li></ul><ul><li>The impulse passes from one part of the heart to another which causes the contraction of muscles to start the pumping action </li></ul>
  3. 3. The cardiac cycle <ul><li>SA node is stimulated </li></ul><ul><li>SA node stimulates the AV node causing AV valves to open and atrium to contract to push blood into ventricle </li></ul><ul><li>AV node passes impulse to Bundle of His and Purkinje fibers causing ventricle to contract to push blood through the semi-lunar valves into aorta or pulmonary artery </li></ul><ul><li>The cycle starts over again </li></ul>
  4. 4. Cardiac efficiency <ul><li>Cardiac output (amount of blood pumped by the heart in one minute) is determined by multiplying the heart rate (beats per minute) by the stroke volume ( the amount of blood pumped out of the left ventricle in one contraction </li></ul><ul><li>CO=HRXSV </li></ul><ul><li>Used to determine the efficiency of the heart. </li></ul><ul><li>What is the CO if a person had a HR of 60 BPM and a SV of 70 mL per beat? </li></ul>
  5. 5. Blood Pressure <ul><li>Pumping action of the heart forces the blood through the vessels under pressure </li></ul><ul><li>The pressure that is exerted is measured with a blood pressure cuff in millimeters of mercury or mmHg. </li></ul><ul><li>BP is measured when ventricles contract (systolic pressure) and when ventricle relaxes (diastolic pressure) </li></ul><ul><li>Example: 120/80 means that the pressure of blood caused by a pumping ventricle is measured at 120 mmHg while the pressure of the blood caused by a relaxing ventricle is 80 mmHg </li></ul>
  6. 6. Taking a blood pressure <ul><li>Put BP cuff on arm and place stethoscope over Brachial artery </li></ul><ul><li>Inflate the BP cuff until about 160 mmHg. This will completely close the artery, stopping all blood flow. </li></ul><ul><li>Slowly let air out of the cuff and listen to when you hear the first sound. This sound is the systolic pressure (first number) </li></ul><ul><li>Continue to slowly let air out until you hear the sound disappear completely. This is the diastolic pressure (second number) </li></ul><ul><li>Record the first number over the second number to give the correct blood pressure. </li></ul>
  7. 7. Systole vs Diastole <ul><li>Systole is when the heart chambers are contracting (pumping). </li></ul><ul><li>Diastole is when the heart chambers are relaxed (filling). </li></ul>
  8. 8. Impulse Conduction through the Heart Figure 20–13
  9. 9. The Sinoatrial (SA) Node <ul><li>In posterior wall of right atrium </li></ul><ul><li>Contains pacemaker cells </li></ul><ul><li>Connected to AV node by internodal pathways </li></ul><ul><li>Begins atrial activation (Step 1) </li></ul>
  10. 10. The Atrioventricular (AV) Node <ul><li>In floor of right atrium </li></ul><ul><li>Receives impulse from SA node (Step 2) </li></ul><ul><li>Delays impulse (Step 3) </li></ul><ul><li>Atrial contraction begins </li></ul>
  11. 11. The AV Bundle <ul><li>In the septum </li></ul><ul><li>Carries impulse to left and right bundle branches : </li></ul><ul><ul><li>which conduct to Purkinje fibers (Step 4) </li></ul></ul><ul><li>And to the moderator band: </li></ul><ul><ul><li>which conducts to papillary muscles </li></ul></ul>
  12. 12. 4. The Purkinje Fibers <ul><li>Distribute impulse through ventricles (Step 5) </li></ul><ul><li>Atrial contraction is completed </li></ul><ul><li>Ventricular contraction begins </li></ul>
  13. 13. Ectopic Pacemaker <ul><li>Abnormal cells </li></ul><ul><li>Generate high rate of action potentials </li></ul><ul><li>Bypass conducting system </li></ul><ul><li>Disrupt ventricular contractions </li></ul>
  14. 14. What electrical events are associated with a normal electrocardiogram?
  15. 15. The Electrocardiogram Figure 20–14b
  16. 16. Electrocardiogram (ECG or EKG) <ul><li>A recording of electrical events in the heart </li></ul><ul><li>Obtained by electrodes at specific body locations </li></ul><ul><li>Abnormal patterns diagnose damage to heart cells/tissue </li></ul>
  17. 17. Features of an ECG <ul><li>P wave: </li></ul><ul><ul><li>atria depolarize </li></ul></ul><ul><li>QRS complex: </li></ul><ul><ul><li>ventricles depolarize </li></ul></ul><ul><li>T wave: </li></ul><ul><ul><li>ventricles repolarize </li></ul></ul>
  18. 18. Time Intervals <ul><li>P–R interval: </li></ul><ul><ul><li>from start of atrial depolarization </li></ul></ul><ul><ul><li>to start of QRS complex </li></ul></ul><ul><li>Q–T interval: </li></ul><ul><ul><li>from ventricular depolarization </li></ul></ul><ul><ul><li>to ventricular repolarization </li></ul></ul>
  19. 19. Cardiac Arrhythmias <ul><li>Abnormal patterns of cardiac electrical activity </li></ul><ul><li>Bradycardia : </li></ul><ul><ul><li>abnormally slow heart rate </li></ul></ul><ul><li>Tachycardia : </li></ul><ul><ul><li>abnormally fast heart rate </li></ul></ul>
  20. 20. KEY CONCEPT (1 of 3) <ul><li>Heart rate is normally established by cells of SA node </li></ul><ul><li>Rate can be modified by autonomic activity, hormones, and other factors </li></ul>
  21. 21. KEY CONCEPT (2 of 3) <ul><li>From the SA node, stimulus is conducted to AV node, AV bundle, bundle branches, and Purkinje fibers before reaching ventricular muscle cells </li></ul>
  22. 22. KEY CONCEPT (3 of 3) <ul><li>Electrical events associated with the heartbeat can be monitored in an electrocardiogram (ECG) </li></ul>
  23. 23. How is the heart supplied with blood?
  24. 24. Blood Supply to the Heart <ul><li>Coronary circulation </li></ul>Figure 20–9
  25. 25. Coronary Circulation <ul><li>Coronary arteries supply blood to muscle tissue of heart </li></ul><ul><li>cardiac veins return the blood from the muscle and tissue of the heart to the systemic circulation. </li></ul><ul><li>Blocka </li></ul>
  26. 26. Heart Attacks <ul><li>A blockage of these coronary arteries causes heart attacks </li></ul><ul><li>Blockages can be held open with a stent </li></ul><ul><li>When blockages are too large for a stent, cardiac bypass surgery is required </li></ul>