Chapter 11 The Heart’s Conduction System and The Cardiac Cycle Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 11 The Heart’s Conduction System and The Cardiac Cycle Lecture Slides in PowerPoint by Jerry L. Cook Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The Cardiovascular System A closed system that contains: 4-chambered heart Blood vessels Functions of the cardiovascular system: Deliver oxygen and nutrients to tissues Remove CO2 and other waste products from tissues

Blood Circulation Figure 11.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.3

The Heart About the size of your fist Location Thoracic cavity between the lungs Apex pointed toward left hip

Visceral pericardium – a membrane lining the outside of the heart The heart is covered by a double serous (connective tissue) membrane Visceral pericardium – a membrane lining the outside of the heart Parietal pericardium – a membrane that lies on the outside of the visceral pericardium Serous fluid fills the space between the two pericardial membranes

The wall of the heart is made of three different types of tissues: EPICARDIUM Outside layer of connective tissue (viscera pericardium) MYOCARDIUM Middle layer made of cardiac muscle ENDOCARDIUM Inner layer made of epithelial tissue (endothelium)

The heart’s conduction system is intrinsic – heart muscle cells contract, without nerve impulses, in a regular, continuous way. Special tissues in the right atrium that set the pace Sinoatrial Node (SA node) Natural pacemaker initiates the contraction (heartbeat) Atrioventricular Node (AV Node) Delays the impulse briefly to allow atria time to finish contracting

The heart’s conduction system is intrinsic – heart muscle cells contract, without nerve impulses, in a regular, continuous way. Ventricle contracts due to the following fibers (in ventricle wall) working together: AV bundle Bundle branches Purkinje fibers

Cardiac Conduction System Heart Contractions Cardiac Conduction System Slide 11.14b Figure 11.5

Cardiac Conduction System Heart Contractions Cardiac Conduction System Slide 11.14b Figure 11.5

Cardiac Conduction System Heart Contractions Cardiac Conduction System Slide 11.14b Figure 11.5

Cardiac Conduction System Heart Contractions Cardiac Conduction System Slide 11.14b Figure 11.5

The Cardiac Cycle Atria contract simultaneously; atria relax, then ventricles contract. Systole = ventricle contraction Diastole = ventricle relaxation

Filling of Heart Chambers – the Cardiac Cycle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.6

Cardiac Output (CO) Amount of blood pumped by each side of the heart in one minute CO = HR x SV * (heart rate) x (stroke volume) * Stroke volume = Volume of blood pumped by each ventricle in one contraction

Regulation of Heart Rate Heart Rate INCREASED by: Sympathetic nervous system – crisis, low blood pressure Hormones – epinephrine, thyroxine Exercise Decreased blood volume

1. The Heart: Regulation of Heart Rate Heart Rate DECREASED by: Parasympathetic nervous system High blood pressure or blood volume Decreased venous return

Cardiac Output Regulation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.7

Heart Excitation Related to ECG Figure 18.17

Electrocardiography Figure 18.16

Lub – first sound, resulting from closing of AV valve right after ventricles are filled Dub – second sound resulting from closure of the Semilunar valve. After which the atria start to fill… and the cycle continues