Chapter 19 Heart Lecture Outline PDF

Chapter 19 Lecture Outline 19.1a General Function _____________________________= heart + blood vessels Transports blood throughout the body Delivery of O2, nutrients; removal of CO2, wastes Providing adequate perfusion ____...

Chapter 19 Lecture Outline 19.1a General Function _____________________________= heart + blood vessels Transports blood throughout the body Delivery of O2, nutrients; removal of CO2, wastes Providing adequate perfusion _____________________________ delivery of blood per time per gram of tissue mL/min/g Adequate perfusion: sufficient delivery to maintain cells’ health Requires continual pumping of the heart and open, healthy vessels 19.1b Overview of Components 1 Blood vessels _____________________________carry blood away from the heart Most (not all) carry _____________________________ blood _____________________________carry blood back to the heart Most (not all) carry _____________________________ blood _____________________________are sites of exchange (for example, of gases) Between blood and air in lungs Between blood and body cells 19.1b Overview of Components 2 Two sides of the _____________________________ Right side receives deoxygenated blood and pumps it to lungs Left side receives oxygenated blood and pumps it to body The heart’s four chambers _____________________________ Superior chambers that receive blood and send it to ventricles _____________________________ Inferior chambers that pump blood away 19.1b Overview of Components 3 _____________________________ Transport blood to and from heart’s chambers _____________________________and_____________________________ Drain deoxygenated blood into right atrium _____________________________ Transports blood from right ventricle Splits into pulmonary arteries _____________________________ Drain oxygenated blood into left atrium _____________________________ Transports blood from left ventricle 19.1b Overview of Components 4 The heart has two sets of valves Ensure one-way flow of blood through heart _____________________________ Sit between atrium and ventricle of each side _____________________________ (tricuspid)  _____________________________ (bicuspid) _____________________________ Sit at boundary of ventricle and arterial trunk _____________________________ located between right ventricle and pulmonary trunk _____________________________ located between left ventricle and the aorta 19.1c Pulmonary and Systemic Circulation _____________________________ Deoxygenated blood from right side of heart to lungs At lungs, blood picks up oxygen and releases carbon dioxide Blood vessels return blood to left side of heart _____________________________ Oxygenated blood from left side of heart to systemic cells At systemic cells (for example, skin, muscles), blood exchanges gases, nutrients, and wastes Blood vessels return blood to right side of heart Basic pattern right heart → lungs → left heart → systemic tissues → right heart 19.2a Location and Position of the Heart Heart is enclosed in pericardium within thoracic cavity Heart sits posterior to sternum left of body midline Between lungs in _____________________________ Slightly rotated: right side more anterior than left _____________________________ postero-superior surface _____________________________ inferior, conical end Projects slightly anteroinferiorly toward left side of body 19.2b The Pericardium 1 The heart is enclosed in three layers (the _____________________________): _____________________________ outermost covering Dense irregular connective tissue Anchors heart and prevents its overfilling _____________________________ Simple squamous epithelium and areolar connective tissue Attaches to fibrous pericardium _____________________________ Simple squamous epithelium and areolar connective tissue Attaches directly to heart Two serous layers continuous and separated by _____________________________ 19.2b The Pericardium 2 The two serous layers continuous and separated by _____________________________, containing _____________________________ Serous fluid acts as lubricant Fibrous pericardium and parietal layer of serous pericardium together form the _____________________________ 19.3a Superficial Features of the Heart 1 Anterior view: chambers and great vessels Right atrium and right ventricle appear prominent  _____________________________ _____________________________(wrinkled extension of atrium) is especially noticeable Portions of _____________________________and left ventricle are also visible Also visible are _____________________________splitting into _____________________________ and _____________________________ _____________________________, _____________________________, and _____________________________ 19.3a Superficial Features of the Heart 2 Posterior view Left atrium and left ventricle prominent Also visible Pulmonary veins attached to left atrium Superior and inferior vena cava, pulmonary arteries Posterior interventricular sulcus Part of coronary sulcus housing coronary sinus 19.3a Superficial Features of the Heart 3 Sulci of the heart _____________________________separates atria from ventricles Groove extending around circumference of heart _____________________________separate left from right ventricles _____________________________on anterior side _____________________________on posterior side Extend from coronary sulcus toward heart apex Grooves contain coronary vessels supplying blood to heart wall 19.3b Layers of the Heart Wall 1 Heart wall varies in thickness Ventricles (pumping chambers) have thicker walls than atria Left ventricle has thicker wall than right ventricle Left must generate high pressure to force blood through systemic circulation; right just pumps to nearby lungs Figure 19.8 19.3b Layers of the Heart Wall 2 Heart wall has three layers: _____________________________(visceral pericardium) Outermost heart layer Simple squamous epithelium and areolar connective tissue _____________________________ Middle layer of heart wall (thickest) Cardiac muscle tissue that contracts to pump blood _____________________________ Covers internal surface of heart and external surface of valves Simple squamous epithelium and areolar connective tissue Continuous with lining of blood vessels 19.3c Heart Chambers 1 Separation of chambers  _____________________________separates left atrium from right atrium _____________________________separates left ventricle from right ventricle _____________________________ Entrances from coronary sinus (carrying blood from heart wall), superior vena cava, and inferior vena cava Exit to right ventricle through right AV valve 19.3c Heart Chambers 2 _____________________________ _____________________________irregular muscular ridges inside ventricle wall _____________________________cone-shaped projections extending from internal ventricle wall (right ventricle typically has 3 of them) Anchor chordae tendineae _____________________________ Thin strands of collagen fibers attaching to AV valve Superior exit to pulmonary trunk through pulmonary semilunar valve 19.3c Heart Chambers 3 _____________________________ Entrances from pulmonary veins Exit to left ventricle through left AV valve _____________________________ Trabeculae carneae on internal wall surface Two papillary muscles anchor chordae tendineae Superior exit to aorta through aortic semilunar valve 19.3d Heart Valves 1 Valves ensure one-way blood flow Two types of heart valves: atrioventricular and semilunar Made of connective tissue cusps (flaps) _____________________________ Prevent backflow to atria Right AV valve = between right atrium and ventricle; also called tricuspid because it has three flaps Left AV (mitral) valve = between left atrium and ventricle; also called bicuspid because it has two flaps AV valves close when ventricles contract, force blood superiorly Papillary muscle and tendinous cords prevent inverting into atria 19.3d Heart Valves 2 _____________________________ Prevent backflow to ventricles Open when ventricles contract and blood forced into arteries Close when ventricles relax Arterial pressure becomes greater than ventricular pressure As blood starts to slide backward it catches cusps and closes valves Pulmonary semilunar valve Located between right ventricle and pulmonary trunk Aortic semilunar valve Located between left ventricle and the aorta Clinical View: Heart Sounds and Heart Murmurs 1 Four normal heart sounds Two familiar sounds, “lubb-dupp,” S1 and S2 S1, closing of AV valves S2, closing of semilunar valves 19.3f Coronary Vessels: Blood Supply Within the Heart Wall 1 _____________________________ delivers blood to heart’s thick wall _____________________________transport oxygenated blood to heart wall _____________________________transport deoxygenated blood away from heart wall toward right atrium 19.4a Microscopic Structure of Cardiac Muscle 1 Myocardium is composed of cardiac muscle tissue Cardiac muscle cells are short, branched House one or two central nuclei Myofilaments arranged in sarcomeres Organization gives rise to striated appearance under microscope Cells are connected with _____________________________ _____________________________ mechanically join cells with protein filaments _____________________________electrically join cells (allow ion flow) to make each heart chamber a functional unit (_____________________________) 19.5a The Heart’s Conduction System 1 _____________________________initiates and conducts electrical events to ensure proper timing of contractions Specialized cardiac muscle cells that have action potentials but do not contract Its activity is influenced by autonomic nervous system 19.5a The Heart’s Conduction System 2 _____________________________initiates heartbeat (pacemaker) Located high in posterior wall of right atrium _____________________________ Located in floor of right atrium (near right AV valve) _____________________________(bundle of His) Extends from AV node though interventricular septum Divides into _____________________________ and _____________________________ _____________________________ Extend from left and right bundles at heart’s apex Travels through walls of ventricles 19.5b Innervation of the Heart 1 _____________________________of medulla oblongata Contains cardioacceleratory and cardioinhibitory centers Receives signals from baroreceptors and chemoreceptors in cardiovascular system Sends signals via sympathetic and parasympathetic pathways Modifies (does not initiate) cardiac activity Influences rate and force of heart’s contractions 19.5b Innervation of the Heart 2 _____________________________decreases heart rate  Starts at medulla’s _____________________________ _____________________________ Relayed via vagus nerves (CN X) _____________________________increases heart rate and force of contraction Starts at medulla’s _____________________________ _____________________________ Relayed via neurons from T1–T5 segments of spinal cord 19.6c Conduction System of the Heart: Spread of the Action Potential 2 Specialized features associated with ventricles Purkinje fibers larger in diameter than other cardiac fibers Action potential extremely rapid Ensures ventricles contract at same time Papillary muscles stimulated to contract immediately Muscles anchor chordae tendinae of AV cusps Start to pull on cusps just prior to increase in pressure in ventricles Stimulation begins at heart apex Ensures blood efficiently ejected toward arterial trunks 19.7a Cardiac Muscle Cells at Rest Cardiac muscle cells Contain Na+/ K+ pumps, Ca2+ pumps, leakage channels for Na+ and K+ Have a resting membrane potential of -90 mV Contain specific voltage-gated channels: Fast voltage-gated Na+ channels Slow voltage-gated Ca2+ channels Voltage-gated K+ channels Voltage channels are closed when cell is at rest 19.7b Electrical and Mechanical Events of Cardiac Muscle Cells 1 Electrical events of cardiac muscle action potential 1) _____________________________ Impulse from conduction system (or gap junctions) opens fast voltage-gated Na+ channels Na+ enters cell changing membrane potential from −90 mV to +30 mV Voltage-gated Na+ channels start to inactivate 2) _____________________________ Depolarization opens voltage-gated K+ and slow voltage-gated Ca2+ channels K+ leaves cardiac muscle cell as Ca2+ enters Stimulates sarcoplasmic reticulum to release more Ca2+ Membrane remains depolarized 19.7b Electrical and Mechanical Events of Cardiac Muscle Cells 2 Electrical events (continued) 1) _____________________________ Voltage-gated Ca2+ channels close while K+ channels remain open Membrane potential goes back to −90 mV 19.7c Repolarization and the Refractory Period Cardiac muscle cannot exhibit tetany Unlike skeletal muscle, cardiac cells have a long _____________________________ Cell cannot fire a new impulse during refractory period  Cardiac muscle cell’s plateau phase leads to refractory period of about 250 ms The heart cell contracts and relaxes before it can be stimulated again Makes sustained (tetanic) contraction impossible 19.7d Electrocardiogram (ECG) 1 _____________________________ Skin electrodes detect electrical signals of cardiac muscle cells Common diagnostic tool Waves _____________________________ Reflects electrical changes of _____________________________originating in SA node _____________________________ Electrical changes associated with _____________________________ Atria also simultaneously repolarizing _____________________________ Electrical change associated with _____________________________ 19.7d Electrocardiogram (ECG) 2 Segments Two segments between waves correspond to plateau phases of cardiac action potentials (no electrical change) _____________________________ Associated with atrial cells’ plateau (atria are contracting) _____________________________ Associated with ventricular plateau (ventricles are contracting) 19.7d Electrocardiogram (ECG) 3 Electrical events of the heart and an ECG Atria Atrial depolarization: recorded as the P wave, muscle cells of atria stimulated to contract Atrial plaeau: recorded as PQ segment, muscle cells of atria contract and relax Atrial repolarization: not visible on ECG Ventricles Ventricular depolarization: recorded as the QRS wave, muscle cells of ventricles stimulated to contract Ventricular plateau: recorded as ST segment, muscle cells of ventricles contract and relax Ventricular repolarization: recorded as T wave 19.7d Electrocardiogram (ECG) 4 Intervals _____________________________ Time from beginning of P wave to beginning of QRS deflection From atrial depolarization to beginning of ventricular depolarization Time to transmit action potential through entire conduction system _____________________________ Time from beginning of QRS to the end of T wave Reflects the time of ventricular action potentials Length depends upon heart rate  Changes may result in _____________________________ (rapid, irregular heart rate) 19.8a Overview of the Cardiac Cycle 1 _____________________________all events in heart from the start of one heart beat to start of the next Includes both _____________________________ (contraction) and _____________________________ (relaxation) Contraction increases pressure; relaxation decreases it Blood moves down its pressure gradient (high to low) Valves ensure that flow is forward (closure prevents backflow) 19.8a Overview of the Cardiac Cycle 2 Ventricular activity is most important driving force _____________________________raises ventricular pressure AV valves pushed closed Semilunar valves pushed open and blood ejected to artery _____________________________lowers ventricular pressure Semilunar valves close No pressure from below keeping them open AV valves open No pressure pushing them closed 19.8b Events of the Cardiac Cycle 1 As the cardiac cycle begins Four chambers at rest Blood returning to both atria Passive filling of ventricles AV valves open Atrial pressure > ventricular pressure Semilunar valves closed Pressure in ventricles < arterial trunk pressure 19.8b Events of the Cardiac Cycle 2 _____________________________ SA node starts atrial excitation Atria contract pushing remaining blood into ventricles Ventricles filled to _____________________________ Atria relax for remainder of cardiac cycle _____________________________ Purkinje fibers initiate ventricular excitation Ventricles contract, pressure rises, and AV valves are pushed closed Ventricular pressure is still less than arterial trunk pressure, so semilunar valves still closed 19.8b Events of the Cardiac Cycle 3 _____________________________ Ventricles continue to contract so that ventricular pressure rises above arterial pressure Semilunar valves forced open as blood moves from ventricles to arterial trunks _____________________________is amount of blood ejected by ventricle _____________________________is amount of blood remaining in ventricle after contraction finishes  ESV = EDV − SV For example 60 mL = 130 mL − 70 mL 19.8b Events of the Cardiac Cycle 4 _____________________________ Ventricles relax and start to expand, lowering pressure Arterial pressure greater than ventricular pressure By sliding back toward ventricles, blood closes semilunar valves AV valves remain closed When all valves are closed, blood neither enters nor leaves and the time is called “isovolumic” 19.8b Events of the Cardiac Cycle 5 _____________________________ All heart chambers are relaxed Atrial blood pressure forces AV valves open and blood flows into ventricles Semilunar valves remain closed since arterial pressure is greater than ventricular pressure 19.8b Events of the Cardiac Cycle 6 _____________________________ Equal amounts of blood are pumped by left and right sides of the heart Left heart pumps blood farther and so must be stronger (thicker) But ejected blood volumes must be the same or _____________________________(swelling) can occur 19.9a Introduction to Cardiac Output 1 _____________________________ Amount of blood pumped by a single ventricle in one minute Measured in liters per minute Measure of effectiveness of cardiovascular system Increases in healthy individuals during exercise Determined by _____________________________(beats per minute) and _____________________________(amount of blood ejected per beat) HR × SV = CO For example, 75 beats/min × 70 ml/beat = 5.25 L/min 19.9a Introduction to Cardiac Output 3 _____________________________ Capacity to increase cardiac output above rest level Subtract cardiac output at rest from output with exercise HR accelerates and stroke volume increases during exercise Gives measure of level of exercise an individual can pursue For example, CO can increase four-fold in healthy, nonathlete and up to seven- fold in athlete 19.9b Variables That Influence Heart Rate 1 Increasing heart rate Sympathetic nerve stimulation Causes norepinephrine (NE) release on heart Causes adrenal to release epinephrine (EPI) and NE NE and EPI bind to nodal cells and increase their firing rate  G-protein, adenylate cyclase, cAMP, protein kinase cascade Phosphorylated Ca2+ channels enhance Ca2+ influx so cell fires sooner 19.9b Variables That Influence Heart Rate 2 Increasing heart rate (continued) Thyroid hormone Increases number of receptors on nodal cells Caffeine Inhibits breakdown of cAMP Nicotine Increases release of norepinephrine Cocaine Inhibits reuptake of norepinephrine (more remains in cleft longer) 19.9b Variables That Influence Heart Rate 3 Decrease heart rate Parasympathetic activity Parasympathetic axons release acetylcholine (ACh) onto nodal cells ACh binds receptors which are K+ channels Channels open, K+ exits cell making it more negative Longer time for nodal cell to reach threshold, so heart rate slower Beta-blocker drugs Interfere with EPI and NE binding to receptors Used to treat high blood pressure 19.9b Variables That Influence Heart Rate 4 Autonomic reflexes Baroreceptors and chemoreceptors send signals to cardiac center Cardiac center influences sympathetic and parasympathetic systems to alter cardiac output as needed _____________________________(Bainbridge reflex) Protects heart from overfilling Baroreceptors in atrial walls stimulated by increased venous return Increased excitation of sympathetic axons to heart Heart rate increase to move blood through quickly (less atrial stretch) 19.9c Variables That Influence Stroke Volume 1 Stroke volume is amount of blood ejected in one beat Stroke volume (SV) is influenced by: venous return and afterload _____________________________ volume of blood returned to the heart Determines amount of ventricular blood prior to contraction Volume determines _____________________________ Pressure stretching heart wall before shortening 19.9c Variables That Influence Stroke Volume 2 _____________________________(continued) _____________________________ As volume increases, the greater stretch of heart wall results in more optimal overlap of thick and thin filaments Heart contracts more forcefully when filled with more blood so SV increases 19.9c Variables That Influence Stroke Volume 3 _____________________________(continued) Decreases with low blood volume (for example, with hemorrhage) or high heart rate Results in smaller blood volume, preload Results in smaller stroke volume 19.9c Variables That Influence Stroke Volume 5 _____________________________ Resistance in arteries to ejection of blood by ventricles Pressure that must be exceeded before blood ejected Atherosclerosis (plaque in vessel linings) increases afterload Seen with aging Smaller arterial lumen exerts greater resistance to movement of blood Results in decreased stroke volume Clinical View: Bradycardia and Tachycardia _____________________________ Persistently low resting heart rate in adults Below 60 beats/minute Abnormal due to: hypothyroidism, electrolyte imbalance, and congestive heart failure _____________________________ Persistently high resting heart rate Over 100 beats/minute Caused by heart disease, fever, and anxiety