Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O2O2 Systemic circulation (to body) Circulation to tissues of head Tissue capillaries Pulmonary circulation (to lungs) Lung capillaries Right side of heart Tissue capillaries O2O2 CO 2 Circulation to tissues of lower body CO 2 O2O2 Left side of heart CO 2

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aortic arch Left pulmonary artery Branches of left pulmonary arteries Pulmonary trunk Pulmonary veins Left atrium Bicuspid valve Left ventricle Interventricular septum Superior vena cava Branches of right pulmonary arteries Aortic semilunar valve Pulmonary veins Right atrium Tricuspid valve Papillary muscles Right ventricle (a) Inferior vena cava Pulmonary semilunar valve

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior vena cava Branches of right pulmonary artery Right pulmonary veins Right atrium Coronary sulcus Right coronary artery Right ventricle Inferior vena cava (a)Anterior view Aortic arch Left pulmonary artery Branches of left pulmonary artery Pulmonary trunk Left pulmonary veins Left atrium Great cardiac vein (in anterior interventricular sulcus) Anterior interventricular artery (in anterior interventricular sulcus) Left ventricle

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Branching muscle fibers Intercalated disks Nucleus of cardiac muscle cell LM 400x Mitochondrion Striations Sarcolemma (cell membrane) Connective tissue (b)(a) Myofibrils Sarcomere Sarcoplasmic reticulum T tubule b: © Ed Reschke

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aortic arch Pulmonary trunk Left atrium Posterior vein of left ventricle Coronary sinus Great cardiac vein Left ventricle Anterior view(b) Right ventricle Small cardiac vein Middle cardiac vein Superior vena cava Right atrium Into right atrium Aortic arch Pulmonary trunk Left coronary artery Left atrium Circumflex artery Left marginal artery Anterior interventricular artery Left ventricle Anterior view(a) Right ventricle Right marginal artery Posterior interventricular artery Right coronary artery Right atrium Superior vena cava Aortic semilunar valve

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – (mV) 12 0 Depolarization phase Na + channels open. K + channels begin to open. Repolarization phase Na + channels close. K + channels continue to open, causing repolarization. K + channels close at the end of repolarization and return the membrane potential to its resting value. Depolarization phase Na + channels open. Ca 2+ channels open. Plateau phase Na + channels close. Some K + channels open, causing repolarization. Ca 2+ channels are open, producing the plateau by slowing further repolarization. Repolarization phase Ca 2+ channels close. Many K + channels open Skeletal MuscleCardiac Muscle Plateau phase Repolarization phase Repolarization phase Depolarization phase –85 (mV) 500 Time (ms) Depolarization phase (a)(b)

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pulmonary semilunar valve Aortic semilunar valve Tricuspid valve Cardiac muscle of the right ventricle Cardiac muscle of the left ventricle Posterior view Bicuspid valve Cardiac skeleton

Fig Action potentials originate in the sinoatrial (SA) node and travel across the wall of the atrium (arrows) from the SA node to the atrioventricular (AV) node. Action potentials pass through the AV node and along the atrioventricular (AV) bundle, which extends from the AV node, through the fibrous skeleton, into the interventricular septum. The AV bundle divides into right and left bundle branches, and action potentials descend to the apex of each ventricle along the bundle branches. Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls. Apex Purkinje fibers Right and left bundle branches Atrioventricular (AV) bundle Sinoatrial (SA) node Atrioventricular (AV) node Left atrium Left ventricle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (mV) R P T Q S QRS complex Time (seconds) QT intervalPQ interval

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aortic arch Left pulmonary artery Pulmonary trunk Right pulmonary veins Left pulmonary veins Left atrium Bicuspid (mitral) valve Left ventricle Chordae tendineae Papillary muscles Interventricular septum Anterior view Inferior vena cava Right ventricle Papillary muscles Tricuspid valve Coronary sinus Right atrium Right pulmonary veins Pulmonary semilunar valve Aortic semilunar valve Branches of right pulmonary artery Superior vena cava

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pulmonary veins Aorta Aortic semilunar valve (closed) (a) Anterior view Left ventricle (relaxed) Cardiac muscle (relaxed) Papillary muscle (relaxed) Left atrium Bicuspid valve (open) Aorta Pulmonary veins Left atrium Bicuspid valve (closed) Chordae tendineae (tension high) Papillary muscle (contracted) Cardiac muscle (contracted) Left ventricle (contracted) Aortic semilunar valve (open) Chordae tendineae (tension low) (b)Anterior view

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Contraction of the ventricles causes pressure in the ventricles to increase. Almost immediately, the AV valves close (the first heart sound). The pressure in the ventricles continues to increase. Continued ventricular contraction causes the pressure in the ventricles to exceed the pressure in the pulmonary trunk and aorta. As a result, the semilunar valves are forced open, and blood is ejected into the pulmonary trunk and aorta. The atria contract and complete ventricular filling. The AV valves open, and blood flows into the ventricles. The ventricles fill to approximately 70% of their volume. At the beginning of ventricular diastole, the ventricles relax, and the semilunar valves close (the second heart sound) Semilunar valves closed Semilunar valves opened AV valves closed AV valves closed Semilunar valves closed AV valves opened Semilunar valves closed AV valves closed Semilunar valves closed AV valves opened

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pulmonary semilunar valve Aortic semilunar valve Bicuspid valve Outline of heart Tricuspid valve © Terry Cockerham/Cynthia Alexander/ Synapse Media Productions

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sensory neurons (green) carry action potentials from baroreceptors to the cardioregulatory center. Chemoreceptors in the medulla oblongata influence the cardioregulatory center. The cardioregulatory center controls the frequency of action potentials in the parasympathetic neurons (red ) extending to the heart. The parasympathetic neurons decrease the heart rate. The cardioregulatory center controls the frequency of action potentials in the sympathetic neurons (blue) extending to the heart. The sympathetic neurons increase the heart rate and the stroke volume. The cardioregulatory center influences the frequency of action potentials in the sympathetic neurons (blue) extending to the adrenal medulla. The sympathetic neurons increase the secretion of epinephrine and some norepinephrine into the general circulation. Epinephrine and norepinephrine increase the heart rate and stroke volume. Adrenal medulla Epinephrine and norepinephrine Circulation Heart SA node Baroreceptors in aorta Carotid body chemoreceptors Baroreceptors in wall of internal carotid artery Cardioregulatory center and chemoreceptors in medulla oblongata Sensory nerve fibers Sensory nerve fibers Sympathetic nerve fibers to adrenal gland

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood pressure (normal range) The SA node and cardiac muscle (the effectors) increase activity and heart rate and stroke volume increase. The SA node and cardiac muscle (the effectors) decrease activity and heart rate and stroke volume decrease. Baroreceptors in the carotid arteries and aorta detect a decrease in blood pressure. The cardioregulatory center in the brain increases sympathetic stimulation of the heart and adrenal medulla and decreases parasympathetic stimulation of the heart. Baroreceptors in the carotid arteries and aorta detect an increase in blood pressure. The cardioregulatory center in the brain decreases sympathetic stimulation of the heart and adrenal medulla and increases parasympathetic stimulation of the heart. Blood pressure (normal range) Blood pressure increases: Homeostasis Disturbed Blood pressure decreases: Homeostasis Disturbed Start here Blood pressure decreases: Homeostasis Restored 5 Blood pressure increases: Homeostasis Restored

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood pH (normal range) The SA node and cardiac muscle (the effectors) increase activity and heart rate and stroke volume increase, increasing blood flow to the lungs. The SA node and cardiac muscle (the effectors) decrease activity and heart rate and stroke volume decrease, reducing blood flow to the lungs Chemoreceptors in the medulla oblongata detect an increase in blood pH (often caused by a decrease in blood CO 2 ). Control centers in the brain decrease stimulation of the heart and adrenal medulla. Chemoreceptors in the medulla oblongata detect a decrease in blood pH (often caused by an increase in blood CO 2 ). Control centers in the brain increase stimulation of the heart and adrenal medulla. Blood pH decreases: Homeostasis Disturbed Blood pH increases: Homeostasis Restored Blood pH decreases: Homeostasis Restored Blood pH (normal range) Start here Blood pH increases: Homeostasis Disturbed