HAP201 Jenkins Chpt 19 Heart (3).pptx

CHAPTER 19: THE CARDIOVASCULAR SYSTEM: THE HEART Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Introduction   For blood to reach body cells and exchange materials with them, it must constantly be pumped by the heart through the body’s blood vessels The heart is a double pump   Th...

CHAPTER 19: THE CARDIOVASCULAR SYSTEM: THE HEART Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Introduction   For blood to reach body cells and exchange materials with them, it must constantly be pumped by the heart through the body’s blood vessels The heart is a double pump   The left side pumps blood through miles of blood vessels in body systemically The right side pumps blood through the lungs, so it can pick up oxygen and unload carbon dioxide; pulmonary circulation Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Location of Heart  Mediastinum of thoracic cavity   Anatomical region between the lungs that extends from the sternum to the vertebral column Situated obliquely   Apex (pointed end) directed inferiorly to the left Base positioned superiorly to the right Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Location of Heart Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Pericardium   Protective membrane structure that surrounds the heart Two principal parts   Fibrous pericardium – tough, dense irregular connective tissue, prevents overstretching and anchors heart in mediastinum Serous pericardium – delicate, double layer serous membranes with serous fluid in thin cavity between membranes    Parietal layer – fused to fibrous pericardium Visceral layer – adheres tightly to heart muscle tissue, also called epicardium as one of layers of heart wall Pericardial fluid – thin, slippery lubricating serous fluid Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Pericardium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Layers of Heart Wall  Epicardium    Myocardium    Superficial, visceral layer of the pericardium Contains blood and lymphatic vessels that supply the heart muscle Middle, cardiac muscle tissue layer Involuntary cardiac muscle fibers organized in bundles that swirl diagonally around the heart Endocardium    Endothelium layer overlying connective tissue Lines heart chambers, heart valves Continuous with endothelia lining blood vessels Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Layers of Heart Wall Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Heart Chambers  Two atria    Two ventricles   Upper chambers receive blood from veins Pouchlike auricle on anterior surface increases blood volume capacity Lower chambers pump blood into arteries Sulci – surface grooves containing blood vessels and fat    Coronary sulcus Anterior interventricular sulcus Posterior interventricular sulcus Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Heart Chambers Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Heart Chambers Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Right Atrium  Receives blood from       Superior vena cava Inferior vena cava Coronary sinus Separated internally from left atrium by interatrial septum, that contains the fossa ovalis (remnant of fetal foramen ovale) Smooth posterior wall, but pectinate muscle ridges anteriorly extending into auricle Blood passes through the tricuspid valve (right atrioventricular valve) into right ventricle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Right Atrium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Right Ventricle    Receives blood from the right atrium Separated internally from the left ventricle by interventricular septum Cusps of tricuspid valve connected to structures in ventricle chamber    Chordae tendineae – tendon-like cords Papillary muscles – cone-shaped trabeculae carneae – significance? Pumps blood through the pulmonary valve (semi-lunar valve) into the pulmonary trunk that carries blood to the lungs Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Right Ventricle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Left Atrium    Receives blood from four pulmonary veins Other side of interatrial septum and same arrangement of pectinate muscles Blood passes through the bicuspid or mitral valve (left atrioventricular valve) into the left ventricle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Left Atrium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Left Ventricle    Receives blood from left atrium Other side of interventricular septum and same arrangement of chordae tendineae and papillary muscle for bicuspid valve cusps Pumps blood through the aortic valve (semilunar valve) into the ascending aorta that carries blood to the heart wall and to the rest of the body  Ligamentum arteriosum connects aorta to pulmonary trunk as a remnant of fetal blood vessel (ductus arteriosus) that shunted blood from the pulmonary trunk to the aorta, bypassing nonfunctioning fetal lungs Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Left Ventricle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Myocardial Thickness and Function  Thickness varies among chambers related to   their function Atrial walls thinner than ventricular walls, delivering blood to ventricles with gravity assist Left ventricle wall thicker than right ventricle wall, pumping blood great distances to all parts of the body in systemic circulation, while right only pumps to lungs a short distance through pulmonary circulation Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Myocardial Thickness and Function Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Heart Valves  Open and close in response to pressure differences across the valves created when chamber of heart contracts or relaxes    Blood flows from areas of high to low pressure Contraction of chamber increases pressure Valves ensure one-way flow of blood   Atrioventricular valves – between atrium and ventricle Semi-lunar valves – between ventricle and artery Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Heart Valves Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Atrioventricular Valves (AV)   Tricuspid (right) and bicuspid (left) valves When open, rounded ends of cusps project into ventricle chamber    Papillary muscles in ventricle are relaxed and chordae tendineae are slack Blood moves through from higher pressure in atria Close when ventricle contracts   Pressure of blood in chamber drives cusps upward until edges meet and close valve Contraction of papillary muscles tightens the chordae tendineae, preventing valve cusps from pushing up into atria chamber and backflow of blood Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Atrioventricular Valves (AV) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Semi-Lunar Valves (SL)     Pulmonary (right) and aortic (left) valves Three moon-shaped cusps prevent backflow Open when pressure in ventricles exceeds pressure in arteries, as ventricles contract Close when ventricle relaxes and back-flowing blood fills the valve cusps    Blood in cusp causes the semilunar valves to contact each other tightly and close the opening Prevents backflow of blood from arteries No similar valve between veins and atria – atrial contraction compresses those openings so blood doesn’t flow from atria into veins Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Semi-Lunar Valves (SL) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Circulations    Flow of blood with each heart beat Two separate, closed circuits so oxygen-rich and oxygen-poor blood do not mix Two circuits in series, so output of one becomes the input of other    Pulmonary circulation Systemic circulation Coronary circulation – heart has its own circulation like other organs because nutrients not able to diffuse quickly enough from blood in chambers to all tissue cell layers of heart wall Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Circulations Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Pulmonary Circulation     Right side of heart is pump Circulation of oxygen-poor blood through the lungs  Unloads CO2  Picks up O2 Right ventricle ejects blood into the pulmonary trunk, then pulmonary arteries, and capillaries where gas exchange occurs Pulmonary veins carry blood back to left atrium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Systemic Circulation   Left side of heart is pump Circulation of oxygen-rich blood through the body     Delivers O2 to all body cells (except for the air sacs in lung) Picks up CO2 Left ventricle ejects blood into the aorta, then through systemic arteries, and capillaries where gas exchange occurs Systemic veins carry blood back to right atrium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Pulmonary Circulation Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Coronary Circulation  Right and left coronary arteries branch from ascending aorta to supply oxygen-rich blood to myocardium of heart     Branches extend in sulci to both atria/ventricle chambers, right/left, and anterior/posterior Anastomoses – connections form where two or more arteries supply the same body region to provide alternate routes in case of obstruction Coronary capillaries – exchange gases and nutrients/wastes Coronary veins  Collect oxygen-poor blood into coronary sinus on posterior of heart, emptying into right atrium Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Coronary Circulation Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Muscle Tissue  Cardiac muscle fibers connected end-to-end via intercalated discs    Autorhythmic fibers    Desmosomes in discs provide strength Gap junctions allow muscle action potentials to conduct from one muscle fiber to its neighbor Form the cardiac conduction system Spontaneously depolarize and generate action potentials ~ slow Na+ leak Contractile fibers  Powerful contractions propel blood Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Muscle Tissue Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Conduction System   Sinoatrial (SA) node pacemaker sets the rhythm of electrical excitation Conduction system provides path for each cycle of cardiac excitation  Progresses through the heart       Sinoatrial (SA) node – right atrial wall Atrioventricular (AV) node – interventricular septum Atrioventricular (AV) bundle – interventricular septum Right and left bundle branches – toward apex Purkinje fibers – from apex upward in myocardium Ensures chambers stimulated to contract in coordinated manner Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Conduction System Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Contraction of Contractile Fibers Mechanism of cardiac contraction similar to skeletal   muscle Phases of action potential     Electrical activity leads to mechanical response    Depolarization – Na+ channels open and ions inflow Plateau – Ca2+ channels open, inflow triggers contraction Repolarization – K+ channels open and ions outflow Anything affecting Ca2+ movement influences strength of cardiac muscle contraction Long refractory period allows chambers to refill with blood ATP mainly from aerobic cellular respiration, but also creatine phosphate with creatine kinase (CK) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Contraction of Contractile Fibers Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Animation Cardiac Conduction You must be connected to the internet to run this animation. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram (ECG or EKG)  Recording of the electrical charges that accompany each heartbeat   Composite of all the action potentials produced by conduction system and cardiac muscle cells during each heartbeat Normal ECG waves    P wave – atrial depolarization QRS complex – onset of ventricular depolarization T wave – ventricular repolarization Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Electrocardiogram (ECG or EKG) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Correlation of ECG Waves with Heart Activity  Diastole –ventricular relaxation  Systole – ventricular contraction  Sequence of systole and diastole  Depolarization of atria – P wave  Atrial systole occurs  Ventricular depolarization – QRS complex  Masks atrial repolarization occurring at same time  Ventricular systole begins; atrial diastole begins  Repolarization of ventricles – T wave  Ventricular diastole occurs Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Correlatio n of ECG Waves with Heart Activity Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Cycle  All events associated with single heartbeat    Two atria contract (systole) and relax (diastole) Two ventricles contract (systole) and relax (diastole) Heart sounds – caused by blood turbulence due to closing of valves   Lubb sound (S1) – closure of both AV valves as ventricles contract (ventricular systole) Dupp sound (S2) – closure of both SL valves as ventricles relax (ventricular diastole) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Cycle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Animation Cardiac Cycle You must be connected to the internet to run this animation. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Pressure and Volume Changes During Cardiac Cycle Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Cardiac Output   Volume of blood ejected each minute from the left ventricle into the aorta or from right ventricle into the pulmonary trunk CO = stroke volume (SV) x heart rate (HR)     SV = volume of blood ejected by the ventricle during each contraction HR = number of heartbeats per minute Entire blood volume flows through pulmonary and systemic circulation each minute CO changes to meet need, changing with exercise and anything that modifies SV or HR Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Animation Cardiac Output You must be connected to the internet to run this animation. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Regulation of Stroke Volume  Three factors regulate and ensure right and left (SV) ventricles pump equal volumes of blood     Preload – stretch on the heart before it contracts Contractility – forcefulness of contraction influenced by ANS, hormones, Ca2+ concentration Afterload - pressure that must be exceeded before the SL valves open and ventricular ejection begins Frank-Starling law of the heart   Greater stretch of ventricular muscle fibers during diastole leads to greater force of contraction during systole Ensures if more blood is returned to heart, more blood is ejected in next heart beat Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Regulation of Heart Rate (HR)  Cardiovascular center in medulla oblongata is origin of nervous system regulation of HR     Chemical regulation of HR    Receives input from proprioceptors, chemoreceptors, and baroreceptors Also input from limbic system and cerebral cortex Autonomic regulation Hormones – epinephrine and norepinephrine from adrenal gland, thyroid hormones Cations – ionic imbalances of Na+, K+, and Ca2+ Other factors  Age, gender, physical fitness, and body temperature Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Autonomic Regulation of  Heart Rate Sympathetic     Cardiac accelerator neurons arising from the cardiovascular center enervate SA node, AV node, and most of myocardium Release norepinephrine Increase heart rate and force of contraction Parasympathetic    Neurons arising from the cardiovascular center reach heart through vagus nerve (Cranial Nerve X) to SA node, AV node, and atrial myocardium Release acetylcholine Decrease heart rate Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Autonomic Regulation of Heart Rate Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. End of Chapter 19 Copyright 2015 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.