EHR519 Week 1 Lecture 2A Intro to the CV System PDF

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WARNING THIS MATERIAL HAS BEEN PRODUCED AND COMMUNICATED TO YOU BY OR ON BEHALF OF CHARLES STURT UNIVERSITY IN ACCORDANCE WITH SECTION 113P OF THE COPYRIGHT ACT (ACT). THE MATERIAL IN THIS COMMUNICATION MAY BY SUBJECT TO COPYRIGHT UNDER THE ACT. ANY FURTHER REPRODUCTION OR COMMUNICATION OF THIS MATERIAL BY YOU MAY BE THE SUBJECT OF COPYRIGHT PROTECTION UNDER THIS ACT. DO NOT REMOVE THIS NOTICE  EHR519 Week 1 Lecture 2A Cardiovascular System and the role of exercise testing and prescription 2 Week one outline 1. Cardiovascular system refresher 2. Prevalence of cardiovascular conditions in Australia 3. Pathophysiological underpinning of the importance of exercise in the management of cardiovascular conditions 1. Endothelial dysfunction 2. Nitric Oxide 3. Inflammation 4. Shear stress 3 Learning Outcomes be able to explain the pathophysiology of cardiovascular and pulmonary conditions as it relates to exercise physiology; be able to outline the risk factors, complications and co-morbidities that must be accounted for when applying exercise interventions to individuals with cardiopulmonary conditions; 4 Cardiovascular system refresher 1. Heart anatomy 2. Conduction system 3. Circulation 5  The Heart 4 chambers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or Right and left atria (auricles display. superior) Right and left ventricles Aorta Right pulmonary Left pulmonary artery Atrioventicular sulcus Separates atria and ventricles artery Superior vena cava Pulmonary trunk Right pulmonary Left pulmonary veins veins Interatrial septum Pulmonary valve Left atrium Interventricular sulcus Overlies the interventricular Right atrium Aortic valve Fossa ovalis Left AV (bicuspid) valve Pectinate muscles Right AV Left ventricle septum that divides the right (tricuspid) valve Papillary muscle and left ventricle Interventricular septum Tendinous cords Endocardium Trabeculae carneae Myocardium Right ventricle Inferior vena cava Epicardium 6  Interatrial septum The Heart Wall that separates atria Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Interventricular septum Muscular wall that separates the ventricles Aorta Right pulmonary artery Left pulmonary artery Pectinate muscles Interatrial ridges of myocardium Superior vena cava Pulmonary trunk Right pulmonary Left pulmonary veins veins in the right atrium and both Pulmonary valve Interatrial septum Left atrium Auricles Right atrium Aortic valve Fossa ovalis Left AV (bicuspid) valve Pectinate muscles Right AV Left ventricle Trabeculae carneae (tricuspid) valve Internal ridges in both ventricles Papillary muscle Interventricular septum Tendinous cords Endocardium Trabeculae carneae Myocardium Right ventricle Two major circulatory circuits Epicardium Inferior vena cava Pulmonary Systemic 7  Interatrial septum Chordae tendineae Pectinate muscles Interventricular septum Papillary muscles Trabeculae carnae Heart Location Cardiovascular System Xray: Posterior-Anterior View Aortic arch Diaphragm Aortic arch Thoracic cage Heart shadow Rt. Heart Lt. Heart Heart apex Aortic ‘knob’ border border  Heart: Right Ventricle CT scan: Axial Heart Pulmonary aa. Rt. Atrium Pulmonary vv. Rt. Ventricle Descending aorta Rt. Coronary a. Ascending aorta Lt. Coronary a.  The Valves Valves ensure a one-way flow of blood Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. through the heart Atrioventricular (AV) valves—control Left AV blood flow between atria and ventricles (bicuspid) valve Right AV valve has three cusps → tricuspid valve Right AV (tricuspid) valve Left AV valve has two cusps → mitral or Fibrous bicuspid valve skeleton Openings to coronary arteries Chordae tendineae: cords connect AV valves to papillary muscles on floor of ventricles Aortic – Prevent AV valves from flipping inside out or valve bulging into the atria when the ventricles contract Pulmonary valve 12  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pulmonary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tendinous © Manfred Kage/Peter Arnold, Inc. cords Aortic Papillary muscle © The McGraw-Hill Companies, Inc. The Heart Wall Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pericardium—double-walled sac (pericardial sac) that encloses the heart Allows heart to beat without friction, provides room to expand, yet resists excessive Pericardial cavity expansion Pericardial Anchored to diaphragm inferiorly and sternum sac: Fibrous anteriorly layer Serous layer Parietal pericardium—outer wall of sac Epicardium Superficial fibrous layer of connective tissue Deep, thin serous layer Visceral pericardium (epicardium)—heart Myocardium covering Endocardium Serous lining of sac turns inward at base of Epicardium heart to cover the heart surface Pericardial sac Pericardial cavity—space inside the pericardial sac filled with 5 to 30 mL of pericardial fluid 14 The Heart Wall Epicardium (visceral pericardium) Serous membrane covering heart Adipose in thick layer in some places Coronary blood vessels travel through this layer Myocardium Layer of cardiac muscle proportional to work load Epicardium – Muscle spirals around heart which produces wringing motion Fibrous skeleton of the heart: framework of collagenous and elastic fibers Myocardium – Provides structural support and attachment for cardiac muscle and anchor for valve tissue – Electrical insulation between atria and ventricles; important in timing and coordination of contractile Endocardium activity Endocardium Smooth inner lining of heart and blood vessels Covers the valve surfaces and is continuous with endothelium of blood vessels 15 Blood Flow Through the Chambers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 1 Blood enters right atrium from superior and inferior venae cavae. 2 Blood in right atrium flows through right Aorta Left pulmonary AV valve into right ventricle. 11 artery 3 Contraction of right ventricle forces 5 5 pulmonary valve open. 9 4 Blood flows through pulmonary valve Pulmonary trunk Superior into pulmonary trunk. vena cava 4 Left pulmonary 6 5 Blood is distributed by right and left veins pulmonary arteries to the lungs, where it Right 6 unloads CO2 and loads O2. pulmonary veins Left atrium 1 Aortic valve 6 Blood returns from lungs via pulmonary veins to left atrium. 3 7 Left AV (bicuspid) valve 7 Blood in left atrium flows through left AV Right valve into left ventricle. 8 atrium Left ventricle 8 Contraction of left ventricle (simultaneous with 2 Right AV step 3 ) forces aortic valve open. (tricuspid) valve 9 Blood flows through aortic valve into Right ascending aorta. ventricle Inferior 10 Blood in aorta is distributed to every organ in 11 vena cava the body, where it unloads O2 and loads CO2. 11 Blood returns to heart via venae cavae.  Lt. Marginal A. Lt. Interventricular A. Lt. Ant. Ventricular A. Coronary Circulation 5% of blood pumped by heart is pumped to the heart itself through the coronary circulation to sustain its strenuous workload 250 mL of blood per minute Left coronary artery (LCA) branches off the ascending aorta Anterior interventricular branch – Supplies blood to both ventricles and anterior two-thirds of the interventricular septum Circumflex branch – Passes around left side of heart in coronary sulcus – Gives off left marginal branch and then ends on the posterior side of the heart Lt. Atrial A. Lt. Post. Ventricular A. Post. Interventricular A. – Supplies left atrium and posterior wall of left ventricle 17  Rt. Ant. Ventricular A. Rt. Marginal A.. Rt. Atrial A. Coronary Circulation Right coronary artery (RCA) branches off the ascending aorta Supplies right atrium and sinoatrial node (pacemaker) Right marginal branch Rt. Conus A. Rt. Post. Ventricular A. Rt. Coronary A. – Supplies lateral aspect of right atrium and ventricle Posterior interventricular branch – Supplies posterior walls of ventricles 18  Venous Drainage 5% to 10% drains directly into heart chambers—right atrium and right ventricle—by way of the thebesian veins The rest returns to right atrium by the following routes: Great cardiac vein – Travels alongside anterior interventricular artery Great Cardiac V. Middle Cardiac V. – Collects blood from anterior portion of heart – Empties into coronary sinus Middle cardiac vein (posterior interventricular) – Found in posterior sulcus – Collects blood from posterior portion of heart – Drains into coronary sinus Left marginal vein – Empties into coronary sinus Coronary sinus – Large transverse vein in coronary sulcus on posterior side of heart – Collects blood and empties into right atrium Lt. Marginal V. Coronary Sinus 19 The Conduction System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 SA node fires. 2 Excitation spreads through Right atrium 1 2 atrial myocardium. Sinoatrial node (pacemaker) Left 3 AV node fires. atrium 2 Purkinje Atrioventricular 3 fibers 4 Excitation spreads down AV node bundle. Bundle Atrioventricular branches 5 Purkinje fibers distribute bundle 4 excitation through 5 ventricular myocardium. Purkinje fibers  Innervation Sympathetic nerves (raise heart rate) Sympathetic pathway to the heart originates in the lower cervical to upper thoracic segments of the spinal cord Continues to adjacent sympathetic chain ganglia Some pass through cardiac plexus in mediastinum Continue as cardiac nerves to the heart Fibers terminate in SA and AV nodes, in atrial and ventricular myocardium, as well as the aorta, pulmonary trunk, and coronary arteries Parasympathetic nerves (slows heart rate) Pathway begins with nuclei of the vagus nerves in the medulla oblongata Extend to cardiac plexus and continue to the heart by way of the cardiac nerves Fibers of right vagus nerve lead to the SA node Fibers of left vagus nerve lead to the AV node Little or no vagal stimulation of the myocardium – Parasympathetic stimulation reduces the heart rate 21  Electrical Behaviour of the Myocardium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 1 Voltage-gated Na+ channels open. 1. Na+ gates open Plateau +20 2 Na+ inflow depolarizes the membrane 4 and triggers the opening of still more Na+ channels, creating a positive feedback cycle and a rapidly rising membrane voltage. 2. Rapid 0 Action potential 5 depolarization 3 Na+ channels close when the cell Membrane potential (mV) depolarizes, and the voltage peaks at –20 Myocardial 3. Na+ gates close nearly +30 mV. relaxation 4 Ca2+ entering through slow Ca2+ –40 2 channels prolongs depolarization of Myocardial 4. Slow Ca2+ membrane, creating a plateau. Plateau falls contraction slightly because of some K+ leakage, but most K+ channels remain closed until end of plateau. –60 Absolute refractory period channels open 5 Ca2+ channels close and Ca2+ is transported –80 1 out of cell. K+ channels open, and rapid K+ outflow returns membrane to its resting potential. 5. Ca2+ channels 0.15 Time (sec).30 close, K+ channels open (repolarization) The Electrocardiogram Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0.8 second R R +1 PQ ST segment segment Millivolts P wave T wave 0 PR Q interval S QT interval QRS interval –1 Atria Ventricles Atria Ventricles contract contract contract contract Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CO2 O2 Pulmonary circuit: right side of heart Carries blood to lungs for gas exchange and back to heart Systemic circuit: left side of heart Pulmonary circuit Supplies oxygenated blood to all tissues of the body and returns it to the heart O2-poor, CO2-rich O2-rich, blood CO2-poor blood Left side of heart Fully oxygenated blood arrives from lungs via Systemic circuit pulmonary veins Blood sent to all organs of the body via aorta CO2 O2 Right side of heart Lesser oxygenated blood arrives from inferior and superior venae cavae Blood sent to lungs via pulmonary trunk  Circulatory System Tunica interna (tunica intima) Lines the blood vessel and is exposed to blood Endothelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – Acts as a selectively permeable barrier Capillaries – Secretes chemicals that stimulate dilation or constriction of the vessel Artery: – Normally repels blood cells and platelets that may adhere to it and Tunica form a clot interna – When tissue around vessel is inflamed, the endothelial cells produce cell-adhesion molecules that induce leukocytes to adhere Tunica to the surface media Causes leukocytes to congregate in tissues where their defensive actions are needed Tunica externa Tunica media Middle layer Nerve Consists of smooth muscle, collagen, and elastic tissue Strengthens vessels and prevents blood pressure from rupturing them Vasomotion: changes in diameter of the blood vessel brought Vein about by smooth muscle Tunica externa Outermost layer 1 mm Consists of loose connective tissue that often merges with that of neighboring blood vessels, nerves, or other organs Anchors the vessel and provides passage for small nerves, lymphatic vessels 25 Arteries Conducting (elastic or large) arteries Biggest arteries Aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries Distributing (muscular or medium) arteries Distributes blood to specific organs Brachial, femoral, renal, and splenic arteries Smooth muscle layers constitute three-fourths of wall thickness Resistance (small) arteries Arterioles: smallest arteries – Control amount of blood to various organs Metarterioles Short vessels that link arterioles to capillaries Muscle cells form a precapillary sphincter about entrance to capillary – Constriction of these sphincters reduces or shuts off blood flow through their respective capillaries 26 Veins Postcapillary venules—smallest veins Even more porous than capillaries so also exchange fluid with surrounding tissues Muscular venules—up to 1 mm in diameter One or 2 layers of smooth muscle in tunica media Have a thin tunica externa Medium veins—up to 10 mm in diameter Thin tunica media and thick tunica externa Tunica interna forms venous valves Large veins—larger than 10 mm Some smooth muscle in all three tunics 27  Capillaries Continuous capillaries: occur in most tissues Endothelial cells have tight junctions forming a continuous tube with intercellular clefts Allow passage of solutes such as glucose Fenestrated capillaries: kidneys, small intestine Organs that require rapid absorption or filtration Endothelial cells riddled with holes called filtration pores (fenestrations) Sinusoids (discontinuous capillaries): liver, bone marrow, spleen Irregular blood-filled spaces with large fenestrations 28  Capillary beds Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillaries organized into networks called Precapillary capillary beds sphincters Thoroughfare channel Usually supplied by a single metarteriole Metarteriole Thoroughfare channel—metarteriole that continues through capillary bed to venule Precapillary sphincters control which beds are well perfused Anastomosis—the point where two blood vessels merge Capillaries Arteriovenous anastomosis (shunt) Venous anastomosis Arteriole Venule Arterial anastomosis (a) Sphincters open 29 Prevalence of cardiovascular disease in Australia 30