Intro to the Cardiovascular System – Heart I (Jahn).pdf

Intro to the Cardiovascular System – Heart I Stephan C. Jahn, Ph.D. Structure of the Heart (Epicardium)  Chambers of the Heart The heart contains four chambers: The two upper chambers are the atria The two lower chambers are the ventricles © 2015 John Wiley & Sons, Inc. Al...

Intro to the Cardiovascular System – Heart I Stephan C. Jahn, Ph.D. Structure of the Heart (Epicardium)  Chambers of the Heart The heart contains four chambers: The two upper chambers are the atria The two lower chambers are the ventricles © 2015 John Wiley & Sons, Inc. All rights reserved. Chambers of the Heart Between the right atrium and left atrium is a thin partition called the interatrial septum (IAS). An interventricular septum (IVS) separates the right ventricle from the left ventricle. © 2015 John Wiley & Sons, Inc. All rights reserved. Valves of the Heart The heart has four valves composed of dense connective tissue covered by endothelium.  Prevent blood from flowing backward, These valves open and close in response to pressure changes as the heart contracts and relaxes. © 2015 John Wiley & Sons, Inc. All rights reserved. Valves of the Heart Atrioventricular (AV) valves lie between the atria and ventricles. Semilunar valves prevent blood in arteries from flowing back into the heart © 2015 John Wiley & Sons, Inc. All rights reserved. Valves of the Heart (Mitral) © 2015 John Wiley & Sons, Inc. All rights reserved. Blood Flow and Blood Supply of the Heart Blood flows through the heart from areas of higher pressure to areas of lower pressure. The movement of blood through the heart is controlled by the  opening and closing of the valves  contraction and relaxation of the myocardium. © 2015 John Wiley & Sons, Inc. All rights reserved. Blood Flow and Blood Supply of the Heart © 2015 John Wiley & Sons, Inc. All rights reserved. Blood Flow and Blood Supply of the Heart © 2015 John Wiley & Sons, Inc. All rights reserved. Conduction System of the Heart The sinoatrial (SA) node, located in the right atrial wall, begins cardiac excitation. This is the natural pacemaker of the heart. The atrioventricular (AV) node, is located in the interatrial septum At the AV node, the action potential slows considerably,  Provides time for the atria to empty their blood into the ventricles. © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram Conduction of action potentials through the heart generates electrical currents that can be picked up by electrodes placed on the skin. A recording of the electrical changes that accompany the heartbeat is called an electrocardiogram, which is abbreviated as either ECG or EKG. © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram Three clearly recognizable waves accompany each heartbeat: P wave, is a small upward deflection on the ECG;  it represents atrial depolarization. Depolarization causes contraction. © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram The second wave, called the QRS complex, begins as a downward deflection (Q). Then continues as a large, upright, triangular wave (R). And ends as a downward wave (S). The QRS complex represents the onset of ventricular depolarization, when the ventricles start to contract. © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram The third wave is the T wave, a dome- shaped upward deflection that indicates ventricular repolarization © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram © 2015 John Wiley & Sons, Inc. All rights reserved.