Cardiovascular Physiology The Heart as a Pump copyright

Hemodynamics is the process of keeping blood continually circulating while varying the amount of

Blood Distribution • Under normal condition blood resides mainly in the veins and venules.

Conduction System of the Heart Specialized tissues in the heart initiate and conduct impulses

Conduction Pathway Sinoatrial (SA) node (AKA “pacemaker”) initiates contractions in the heart. This node

Conduction Pathway The impulse is accelerated as it passes to the AV bundle (bundle

Pacemakers Although the SA node can maintain intrinsic rhythm it is also influenced by

ECG or EKG • Electrocardiogram is a diagnostic tool that monitors the electrical activity

ECG Waves P wave- depolarization of the atria (atrial contraction) QRS complexventricular depolarization (ventricular

Abnormal Heart Rates Dysrythmia/arrythmia abnormal heart beat Bradycardia-abnormally slow heart Bradycardia rate, <50 Tachycardia-

Cardiac Cycle Systole-contraction part of the heartbeat. Diastole- relaxation part of the heartbeat. Normal

Cardiac Cycle 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 12

Heart Sounds The sound of the heart beat is usually described as “lub-dub. ”

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Hemodynamics is the process of keeping blood continually circulating while varying the amount of blood to regions that need more or less. Ex: digestion and exercise 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 2

Blood Distribution • Under normal condition blood resides mainly in the veins and venules. • Changes in activity can cause a shunting of blood to where it is needed. – Ex: digestion, exercise, SAT tests • The spleen acts a reservoir of blood • Hypovolemic shock is caused by sudden, drastic drop in blood pressure 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 3

Conduction Pathway Sinoatrial (SA) node (AKA “pacemaker”) initiates contractions in the heart. This node is at the junction of the right atrium and the coronary sinus, hence its name. The impulse travels through the interatrial bundles and causes atrial contraction. A slowed impulse reaches the atrioventricular (AV) node via the internodal bundles. 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 5

Conduction Pathway The impulse is accelerated as it passes to the AV bundle (bundle of His). The impulse then reaches the Purkinje fibers causing ventricular contractions. 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 6

Pacemakers Although the SA node can maintain intrinsic rhythm it is also influenced by autonomic impulses and hormones. If needed, the AV node or Purkinje fibers take over. Artificial pacemakers keep the heart beating at a minimum rate. A normal resting heart rate is around 75 bpm. 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 7

ECG Waves P wave- depolarization of the atria (atrial contraction) QRS complexventricular depolarization (ventricular contraction) T wave- represents repolarization of the ventricles 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 9

Abnormal Heart Rates Dysrythmia/arrythmia abnormal heart beat Bradycardia-abnormally slow heart Bradycardia rate, <50 Tachycardia- unusually fast heart rate, can be caused by stimulants, caffeine, stress Fibrillation arrythmis in which heart begins to quiver, potentially fatal Asystole- no heart beat, flatline 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. Digitalis is medicine made from the foxglove plant used to strengthen the heart beat and control irregular rhythms. 10

Cardiac Cycle Systole-contraction part of the heartbeat. Diastole- relaxation part of the heartbeat. Normal blood pressure 120/80 Hypertension-High blood pressure Atrial Contractions- occurs simultaneously, cuspid valves open and ventricles relax Ventricular Contractions-occur simultaneously as semilunar valves open 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 11

Heart Sounds The sound of the heart beat is usually described as “lub-dub. ” The lub part is caused by closing of the cuspid valves. The dub is caused by the closing of the semilunar valves. 9/16/2020 copyright 2006 www. brainybetty. com; All Rights Reserved. 13