C h a p t e r 20 The Heart PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc.,

C h a p t e r 20 The Heart PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Introduction to Cardiovascular System
The Pulmonary Circuit Carries blood to and from gas exchange surfaces of lungs The Systemic Circuit Carries blood to and from the body Blood alternates between pulmonary circuit and systemic circuit Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Three Types of Blood Vessels Arteries Carry blood away from heart Veins Carry blood to heart Capillaries Networks between arteries and veins Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Capillaries Also called exchange vessels Exchange materials between blood and tissues Materials include dissolved gases, nutrients, wastes Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Four Chambers of the Heart Right atrium Collects blood from systemic circuit Right ventricle Pumps blood to pulmonary circuit Left atrium Collects blood from pulmonary circuit Left ventricle Pumps blood to systemic circuit Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Great veins and arteries at the base
Pointed tip is apex Surrounded by pericardial sac Sits between two pleural cavities in the mediastinum Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 20–2c

Anatomy of the Heart The Pericardium
Double lining of the pericardial cavity Parietal pericardium Outer layer Forms inner layer of pericardial sac Visceral pericardium Inner layer of pericardium Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 20–2c

Anatomy of the Heart The Pericardium Pericardial cavity
Is between parietal and visceral layers Contains pericardial fluid Pericardial sac Fibrous tissue Surrounds and stabilizes heart Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Superficial Anatomy of the Heart Atria Sulci
Thin-walled Expandable outer auricle (atrial appendage) Sulci Coronary sulcus: divides atria and ventricles Anterior interventricular sulcus and posterior interventricular sulcus: separate left and right ventricles contain blood vessels of cardiac muscle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–3a The Superficial Anatomy of the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–3b The Superficial Anatomy of the Heart

Anatomy of the Heart Figure 20–3c The Superficial Anatomy of the Heart

Anatomy of the Heart The Heart Wall Epicardium (outer layer)
Visceral pericardium Covers the heart Myocardium (middle layer) Muscular wall of the heart Concentric layers of cardiac muscle tissue Atrial myocardium wraps around great vessels Two divisions of ventricular myocardium Endocardium (inner layer) Simple squamous epithelium Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–4 The Heart Wall

Anatomy of the Heart Cardiac Muscle Tissue Intercalated discs
Interconnect cardiac muscle cells Secured by desmosomes Linked by gap junctions Convey force of contraction Propagate action potentials Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–5 Cardiac Muscle Cells

Anatomy of the Heart Characteristics of Cardiac Muscle Cells
Small size Single, central nucleus Branching interconnections between cells Intercalated discs Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Internal Anatomy and Organization
Interatrial septum: separates atria Interventricular septum: separates ventricles Atrioventricular (AV) valves Connect right atrium to right ventricle and left atrium to left ventricle The fibrous flaps that form bicuspid (2) and tricuspid (3) valves Permit blood flow in one direction: atria to ventricles The Heart: Valves Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Right Atrium Superior vena cava
Receives blood from head, neck, upper limbs, and chest Inferior vena cava Receives blood from trunk, viscera, and lower limbs Coronary sinus Cardiac veins return blood to coronary sinus Coronary sinus opens into right atrium Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Right Atrium Foramen ovale
Before birth, is an opening through interatrial septum Connects the two atria Seals off at birth, forming fossa ovalis Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Right Atrium Pectinate muscles
Contain prominent muscular ridges On anterior atrial wall and inner surfaces of right auricle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Right Ventricle
Free edges attach to chordae tendineae from papillary muscles of ventricle Prevent valve from opening backward Right atrioventricular (AV) Valve Also called tricuspid valve Opening from right atrium to right ventricle Has three cusps Prevents backflow Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Right Ventricle Trabeculae carneae
Muscular ridges on internal surface of right (and left) ventricle Includes moderator band: ridge contains part of conducting system coordinates contractions of cardiac muscle cells Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Pulmonary Circuit
Conus arteriosus (superior end of right ventricle) leads to pulmonary trunk Pulmonary trunk divides into left and right pulmonary arteries Blood flows from right ventricle to pulmonary trunk through pulmonary valve Pulmonary valve has three semilunar cusps Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Left Atrium
Blood gathers into left and right pulmonary veins Pulmonary veins deliver to left atrium Blood from left atrium passes to left ventricle through left atrioventricular (AV) valve A two-cusped bicuspid valve or mitral valve Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Left Ventricle
Holds same volume as right ventricle Is larger; muscle is thicker and more powerful Similar internally to right ventricle but does not have moderator band Systemic circulation Blood leaves left ventricle through aortic valve into ascending aorta Ascending aorta turns (aortic arch) and becomes descending aorta Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–6c The Sectional Anatomy of the Heart.

Anatomy of the Heart Structural Differences between the Left and Right Ventricles Right ventricle wall is thinner, develops less pressure than left ventricle Right ventricle is pouch-shaped, left ventricle is round Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Heart Valves
Two pairs of one-way valves prevent backflow during contraction Atrioventricular (AV) valves Between atria and ventricles Blood pressure closes valve cusps during ventricular contraction Papillary muscles tense chordae tendineae: prevent valves from swinging into atria Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 20–8

Anatomy of the Heart The Heart Valves Semilunar valves
Pulmonary and aortic tricuspid valves Prevent backflow from pulmonary trunk and aorta into ventricles Have no muscular support Three cusps support like tripod Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Figure 20–8

Anatomy of the Heart Aortic Sinuses At base of ascending aorta
Sacs that prevent valve cusps from sticking to aorta Origin of right and left coronary arteries Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–8a Valves of the Heart

Anatomy of the Heart Figure 20–8b Valves of the Heart

Anatomy of the Heart Figure 20–8c Valves of the Heart

Anatomy of the Heart Connective Tissues and the Cardiac (Fibrous) Skeleton Physically support cardiac muscle fibers Distribute forces of contraction Add strength and prevent overexpansion of heart Elastic fibers return heart to original shape after contraction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Cardiac (Fibrous) Skeleton
Four bands around heart valves and bases of pulmonary trunk and aorta Stabilize valves Electrically insulate ventricular cells from atrial cells Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Blood Supply to the Heart = Coronary Circulation Coronary arteries and cardiac veins Supplies blood to muscle tissue of heart Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Coronary Arteries Left and right
Originate at aortic sinuses High blood pressure, elastic rebound forces blood through coronary arteries between contractions Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Right Coronary Artery Supplies blood to
Right atrium Portions of both ventricles Cells of sinoatrial (SA) and atrioventricular nodes Marginal arteries (surface of right ventricle) Posterior interventricular artery Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Left Coronary Artery Supplies blood to
Left ventricle Left atrium Interventricular septum Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Two main branches of left coronary artery
Circumflex artery Anterior interventricular artery Arterial Anastomoses Interconnect anterior and posterior interventricular arteries Stabilize blood supply to cardiac muscle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart The Cardiac Veins Great cardiac vein
Drains blood from area of anterior interventricular artery into coronary sinus Anterior cardiac veins Empties into right atrium Posterior cardiac vein, middle cardiac vein, and small cardiac vein Empty into great cardiac vein or coronary sinus Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Anatomy of the Heart Figure 20–9a Coronary Circulation

Anatomy of the Heart Figure 20–9b Coronary Circulation

Anatomy of the Heart Figure 20–9c Coronary Circulation

The Conducting System Heartbeat A single contraction of the heart
The entire heart contracts in series First the atria Then the ventricles Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Two Types of Cardiac Muscle Cells
Controls and coordinates heartbeat Contractile cells Produce contractions that propel blood Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The Cardiac Cycle
Begins with action potential at SA node Transmitted through conducting system Produces action potentials in cardiac muscle cells (contractile cells) Electrocardiogram (ECG) Electrical events in the cardiac cycle can be recorded on an electrocardiogram (ECG) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Figure 20–11 An Overview of Cardiac Physiology

The Conducting System A system of specialized cardiac muscle cells
Initiates and distributes electrical impulses that stimulate contraction Automaticity Cardiac muscle tissue contracts automatically Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Structures of the Conducting System
Sinoatrial (SA) node - wall of right atrium Atrioventricular (AV) node - junction between atria and ventricles Conducting cells - throughout myocardium Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Conducting Cells Interconnect SA and AV nodes
Distribute stimulus through myocardium In the atrium Internodal pathways In the ventricles AV bundle and the bundle branches Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Prepotential Also called pacemaker potential
Resting potential of conducting cells Gradually depolarizes toward threshold SA node depolarizes first, establishing heart rate Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Figure 20–12 The Conducting System of the Heart

The Conducting System Heart Rate
SA node generates 80–100 action potentials per minute Parasympathetic stimulation slows heart rate AV node generates 40–60 action potentials per minute Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The Sinoatrial (SA) Node
In posterior wall of right atrium Contains pacemaker cells Connected to AV node by internodal pathways Begins atrial activation (Step 1) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The Atrioventricular (AV) Node
In floor of right atrium Receives impulse from SA node (Step 2) Delays impulse (Step 3) Atrial contraction begins Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The AV Bundle In the septum
Carries impulse to left and right bundle branches Which conduct to Purkinje fibers (Step 4) And to the moderator band Which conducts to papillary muscles Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Purkinje Fibers
Distribute impulse through ventricles (Step 5) Atrial contraction is completed Ventricular contraction begins Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Abnormal Pacemaker Function
Bradycardia: abnormally slow heart rate Tachycardia: abnormally fast heart rate Ectopic pacemaker Abnormal cells Generate high rate of action potentials Bypass conducting system Disrupt ventricular contractions Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Electrocardiogram (ECG or EKG)
A recording of electrical events in the heart Obtained by electrodes at specific body locations Abnormal patterns diagnose damage Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Features of an ECG P wave QRS complex T wave
Atria depolarize QRS complex Ventricles depolarize T wave Ventricles repolarize Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Time Intervals Between ECG Waves P–R interval
From start of atrial depolarization To start of QRS complex Q–T interval From ventricular depolarization To ventricular repolarization Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Contractile Cells
Purkinje fibers distribute the stimulus to the contractile cells, which make up most of the muscle cells in the heart Resting Potential Of a ventricular cell: about –90 mV Of an atrial cell: about –80 mV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Refractory Period Absolute refractory period
Long Cardiac muscle cells cannot respond Relative refractory period Short Response depends on degree of stimulus Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System Timing of Refractory Periods
Length of cardiac action potential in ventricular cell 250–300 msecs: 30 times longer than skeletal muscle fiber long refractory period prevents summation and tetany Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The Role of Calcium Ions in Cardiac Contractions
Contraction of a cardiac muscle cell is produced by an increase in calcium ion concentration around myofibrils Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

20% of calcium ions required for a contraction Calcium ions enter plasma membrane during plateau phase Arrival of extracellular Ca2+ Triggers release of calcium ion reserves from sarcoplasmic reticulum Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

As slow calcium channels close Intracellular Ca2+ is absorbed by the SR Or pumped out of cell Cardiac muscle tissue Very sensitive to extracellular Ca2+ concentrations Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Conducting System The Energy for Cardiac Contractions
Aerobic energy of heart From mitochondrial breakdown of fatty acids and glucose Oxygen from circulating hemoglobin Cardiac muscles store oxygen in myoglobin Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Cardiac cycle = The period between the start of one heartbeat and the beginning of the next Includes both contraction and relaxation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Phases of the Cardiac Cycle Within any one chamber
Systole (contraction) Diastole (relaxation) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Figure 20–16 Phases of the Cardiac Cycle

The Cardiac Cycle Blood Pressure In any chamber
Rises during systole Falls during diastole Blood flows from high to low pressure Controlled by timing of contractions Directed by one-way valves Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Cardiac Cycle and Heart Rate At 75 beats per minute
Cardiac cycle lasts about 800 msecs When heart rate increases All phases of cardiac cycle shorten, particularly diastole Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Eight Steps in the Cardiac Cycle Atrial systole
Atrial contraction begins Right and left AV valves are open Atria eject blood into ventricles Filling ventricles Atrial systole ends AV valves close Ventricles contain maximum blood volume Known as end-diastolic volume (EDV) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Eight Steps in the Cardiac Cycle Ventricular systole
Isovolumetric ventricular contraction Pressure in ventricles rises AV valves shut Ventricular ejection Semilunar valves open Blood flows into pulmonary and aortic trunks Stroke volume (SV) = 60% of end-diastolic volume Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Eight Steps in the Cardiac Cycle
Ventricular pressure falls Semilunar valves close Ventricles contain end-systolic volume (ESV), about 40% of end-diastolic volume Ventricular diastole Ventricular pressure is higher than atrial pressure All heart valves are closed Ventricles relax (isovolumetric relaxation) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Eight Steps in the Cardiac Cycle
Atrial pressure is higher than ventricular pressure AV valves open Passive atrial filling Passive ventricular filling Cardiac cycle ends The Heart: Cardiac Cycle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Heart Sounds S1 S2 S3, S4 Loud sounds
Produced by AV valves S2 Produced by semilunar valves S3, S4 Soft sounds Blood flow into ventricles and atrial contraction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Cardiac Cycle Figure 20–18 Heart Sounds

Cardiodynamics The movement and force generated by cardiac contractions End-diastolic volume (EDV) End-systolic volume (ESV) Stroke volume (SV) SV = EDV – ESV Ejection fraction The percentage of EDV represented by SV Cardiac output (CO) The volume pumped by left ventricle in 1 minute Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Figure 20–19 A Simple Model of Stroke Volume

Cardiodynamics Cardiac Output CO = HR X SV
CO = cardiac output (mL/min) HR = heart rate (beats/min) SV = stroke volume (mL/beat) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Factors Affecting Cardiac Output Cardiac output
Adjusted by changes in heart rate or stroke volume Heart rate Adjusted by autonomic nervous system or hormones Stroke volume Adjusted by changing EDV or ESV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Figure 20–20 Factors Affecting Cardiac Output

Cardiodynamics Factors Affecting the Heart Rate Autonomic innervation
Cardiac plexuses: innervate heart Vagus nerves (X): carry parasympathetic preganglionic fibers to small ganglia in cardiac plexus Cardiac centers of medulla oblongata: cardioacceleratory center controls sympathetic neurons (increases heart rate) cardioinhibitory center controls parasympathetic neurons (slows heart rate) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Autonomic Innervation Cardiac reflexes
Cardiac centers monitor: blood pressure (baroreceptors) arterial oxygen and carbon dioxide levels (chemoreceptors) Cardiac centers adjust cardiac activity Autonomic tone Dual innervation maintains resting tone by releasing ACh and NE Fine adjustments meet needs of other systems Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Figure 20–21 Autonomic Innervation of the Heart

Cardiodynamics Effects on the SA Node
Sympathetic and parasympathetic stimulation Greatest at SA node (heart rate) Membrane potential of pacemaker cells Lower than other cardiac cells Rate of spontaneous depolarization depends on Resting membrane potential Rate of depolarization ACh (parasympathetic stimulation) Slows the heart NE (sympathetic stimulation) Speeds the heart Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Figure 20–22 Autonomic Regulation of Pacemaker Function

Cardiodynamics Atrial Reflex Also called Bainbridge reflex
Adjusts heart rate in response to venous return Stretch receptors in right atrium Trigger increase in heart rate Through increased sympathetic activity Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Hormonal Effects on Heart Rate
Increase heart rate (by sympathetic stimulation of SA node) Epinephrine (E) Norepinephrine (NE) Thyroid hormone Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Factors Affecting the Stroke Volume
The EDV: amount of blood a ventricle contains at the end of diastole Filling time: duration of ventricular diastole Venous return: rate of blood flow during ventricular diastole Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Preload
The degree of ventricular stretching during ventricular diastole Directly proportional to EDV Affects ability of muscle cells to produce tension Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics The EDV and Stroke Volume At rest With exercise
EDV is low Myocardium stretches less Stroke volume is low With exercise EDV increases Myocardium stretches more Stroke volume increases Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics The Frank–Starling Principle Physical Limits
As EDV increases, stroke volume increases Physical Limits Ventricular expansion is limited by Myocardial connective tissue The cardiac (fibrous) skeleton The pericardial sac Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics End-Systolic Volume (ESV)
The amount of blood that remains in the ventricle at the end of ventricular systole is the ESV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Three Factors That Affect ESV Preload Contractility
Ventricular stretching during diastole Contractility Force produced during contraction, at a given preload Afterload Tension the ventricle produces to open the semilunar valve and eject blood Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Effects of Autonomic Activity on Contractility
Sympathetic stimulation NE released by postganglionic fibers of cardiac nerves Epinephrine and NE released by suprarenal (adrenal) medullae Causes ventricles to contract with more force Increases ejection fraction and decreases ESV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Effects of Autonomic Activity on Contractility
Parasympathetic activity Acetylcholine released by vagus nerves Reduces force of cardiac contractions Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Hormones Many hormones affect heart contraction
Pharmaceutical drugs mimic hormone actions Stimulate or block beta receptors Affect calcium ions (e.g., calcium channel blockers) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Afterload
Is increased by any factor that restricts arterial blood flow As afterload increases, stroke volume decreases Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Figure 20–23 Factors Affecting Stroke Volume

Cardiodynamics Heart Rate Control Factors Autonomic nervous system
Sympathetic and parasympathetic Circulating hormones Venous return and stretch receptors Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics Stroke Volume Control Factors EDV ESV Filling time
Rate of venous return ESV Preload Contractility Afterload Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiodynamics The Heart and Cardiovascular System
Cardiovascular regulation Ensures adequate circulation to body tissues Cardiovascular centers Control heart and peripheral blood vessels Cardiovascular system responds to Changing activity patterns Circulatory emergencies Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

C h a p t e r 20 The Heart PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc.,

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C h a p t e r 20 The Heart PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc.,

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Presentation on theme: "C h a p t e r 20 The Heart PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc.,"— Presentation transcript:

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