Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Heart failure wikipedia , lookup
Electrocardiography wikipedia , lookup
Management of acute coronary syndrome wikipedia , lookup
Antihypertensive drug wikipedia , lookup
Mitral insufficiency wikipedia , lookup
Coronary artery disease wikipedia , lookup
Artificial heart valve wikipedia , lookup
Quantium Medical Cardiac Output wikipedia , lookup
Cardiac surgery wikipedia , lookup
Lutembacher's syndrome wikipedia , lookup
Heart arrhythmia wikipedia , lookup
Dextro-Transposition of the great arteries wikipedia , lookup
Histology • Elongated branching cells containing 1-2 central nuclei • Contains actin and myosin • Intercolated discs for specialized cell to cell communication • Desmosomes hold together cells and gap junctions allow AP like propogation • Electrically, cardiac muscle acts as single unit Fig. 20.12 Functions • Generate blood pressure • Routing blood to keep separated systemic from pulmonary blood • Ensuring one way blood flow with valves • Regulating blood supply to parts of the body – Changes is rate and force of contraction matches the changing metabolic needs of the body Fig. 20.1 Anatomy • Pericardial Sac - parietal pericardium – Fibrous Layer – outer layer consisting of tough, fibrous connective tissue • prevents over distension of the heart • provides a protective membrane • anchors the heart in the mediastinum – Serous Layer - 2 layers - (parietal and visceral layer) continuous with the epicardium - adheres to the heart • Pericardial Cavity - a space between the parietal and the visceral layer of the heart filled with pericardial fluid - helps to prevent friction Fig. 20.3 Layers of the Heart • Three Layers – epicardium - external layer – myocardium - middle layer - muscle tissue layer responsible for contraction – endocardium - inner layer - covers valves of the heart, the inside of the myocardium and the tendons of the valves, continuous with the endothelial lining of the large blood vessels Fig. 20.4 Chambers of the Heart • Right and Left ATRIUM - upper chambers - Thin muscle walls - low pressure – auricle - (dog's ear) appendage in the atrium that increases atrium surface area – interatrial septum - separates R and L atrium – fossa ovalis - a depression on the septum which corresponds with the foramen ovali - an opening in the interatrial septum of the fetus Chambers of the Heart • Right and Left VENTRICLES - lower chambers much greater pressure – interventricular septum - separates R and L ventricles – L walls are even thicker than the R walls because it must pump blood through the 1000's miles of blood vessels Fig. 20.7 Great Vessels and Blood Movement • Arteries carry blood away from the heart, veins carry blood toward the heart • Right Atrium • superior vena cava • inferior vena cava • coronary sinus Blood Flow • Blood travels through the right Atrioventricular valve (A-V , Tricuspid) into the R ventricle. The R ventricle contracts and pumps the blood through the pulmonary semilunar valve into the pulmonary trunk, the pulmonary trunk divides into the R and L pulmonary arteries, which lead to the lungs Blood Flow Cont’d • In the lungs the blood releases CO2 and takes up O2 - returns to the heart via 4 pulmonary veins - L atrium - blood flows through the L A-V valve (Bicuspid valve, mitral valve) into the L ventricle - the left ventricle pumps the blood out through the aortic semilunar valve - to the ascending aorta - feeds into the coronary arteries, aortic arch, and the systemic circulation system Fig. 20.10 Valves • • • • • Permit blood flow only in one direction Tricuspid ( R A-V) - 3 flaps (cusps) Bicuspid (L A-V, mitral) - 2 cusps Semilunar – pulmonary, aortic 3 flaps (cusps) Cordae tendineae (cords) - that attach the valve cusps to the papillary muscles, which keep the valves from bring forced back into the atria Fig. 20.9 Blood Supply of the Heart • Coronary circulation - 2 major vessels that branch off the ascending aorta. First vessels above the aortic semilunar valve – most important to make sure the heart has blood Fig. 20.6 Blood Supply of the Heart • Very few anastomoses (outlets) between the large branches of the arteries. If the artery is blocked little or no blood can reach cells - they become ischemic (deprived of 02) and may die myocardial infarction - MI. Heart loses some of its contractility, active tissue is replaced by scar tissue • Anastomoses – provide a secondary blood supply for the capillary beds. Arterial anastomoses can occur in the brain, coronary circulation, or peripheral circulation (often due to increase demand – exercise – “use it or lose it”) Fig. 20.a Blood Supply of the Heart • Angina pectoris "chest pain"- occurs when coronary circulation is reduced: – vasoconstriction - stress, smoking – blockage in vessel - thrombus, embolus, plaque – reduced blood flow to heart - exercising after consuming a large meal • Remedy - take nitroglycerin which dilates coronary blood vessels, will result in increase blood flow Conduction System • Autonomic nervous system increases or decreases the time it takes to complete a cardiac cycle but it does not initiate the contraction. SA node initiates AP @ 70-80 BPM • The conduction system consists of specialized cardiac muscle cells - its sole purpose is conduction of cardiac impulses. – Pacemaker cells Conduction System • Sinoatrial Node - SA node - pacemaker – 100's of cells located in R atrium near the opening of the superior vena cava – Possess an intrinsic rhythm – They initiate each cardiac cycle – The impulse the SA node initiates spreads out over both atria causing them to contract and also depolarizing the AV node Fig. pf 20.13 Conduction System • Atrioventricular node - AV node - located near the inferior portion of the interatrial septum one of the last parts of the R atrium to be depolarized • Atrioventricular Bundle - AV bundle (Bundle of His) • Purkinje Fibers ELECTROCARDIOGRAM • ECG \ EKG • Impulses through the heart's conduction system can be recorded on the body's surface. Each portion of the cardiac cycle produces a different electrical impulse • P wave - indicates artial depolarization (Contraction) SA node fires - impulse travels through atria - atria contract after P wave begins ELECTROCARDIOGRAM • QRS complex - deflection wave - represents ventricular depolarization - (Contraction) – The spread of electrical impulse from AV node →bundle of his → bundle branches →purkinje fibers→ myocardial cells and papillary muscles. QRS complex begins with a downward deflection, continues as a large upright triangular wave and ends as a downward wave at its base. The magnitude of the QRS complex masks the deflection of atrial repolarization.(Relaxation) • T wave - indicates ventricular repolarization (Relaxation) Fig. 20.16 Fig. 20.17b Cardiac Cycle • Heart is two pumps that work together, right and left half • Repetitive contraction (systole) and relaxation (diastole) of heart chambers • Blood moves through circulatory system from areas of higher to lower pressure. – Contraction of heart produces the pressure Starling's Law of the Heart • Increasing the length of the cardiac muscle fibers intensifies the force of the ventricular contraction. During exercise: ↑blood flow = ↑ fiber length = ↑ contraction strength • “More in = more out”, Blood flow can increase from 4-6 L/M to 18-30 L/M during exercise Regulation of Heart Rate • Cardioaccelatory center - located in medulla sympathetic fibers - release of norepinephrine causes an increase in heart rate and contractility (NE increases the force of contraction) • Cardioinhibitory center - located in medulla parasympathetic fibers - release acetylcholine which causes a decrease in HR and contractility. – Bradycardia - HR less than 60 BPM Fig. pf 20.22 Regulation of Heart Rate • Pressoreceptors (baroreceptors) - responsible for maintaining homeostasis between the systems. – Carotid sinus maintains normal BP and O2 levels in the brain. Contains baroreceptors and chemoreceptors at the bifurcation of the carotid arteries Fig. pf 20.22 Cardiac Arrhythmias • Tachycardia: Heart rate in excess of 100bpm • Bradycardia: Heart rate less than 60 bpm • Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration • Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people Effects of Aging on the Heart • Gradual changes in heart function, minor under resting condition, more significant during exercise • Hypertrophy of left ventricle • Maximum heart rate decreases • Increased tendency for valves to function abnormally and arrhythmias to occur • Increased oxygen consumption required to pump same amount of blood Fig. 20.11