BS-PAR3615_W2025 Paramedicine - Medical Physiology II Lecture 2 PDF

PAR3615 Paramedicine – Medical Physiology II W2025 Lecture 2 Cardiovascular I  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright protection, and as such cannot be used and posted for publi...

PAR3615 Paramedicine – Medical Physiology II W2025 Lecture 2 Cardiovascular I  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright protection, and as such cannot be used and posted for public dissemination without prior permission from the College. For clarity, these protections are automatic once a work is created, and applies whether or not a copyright statement appears on the material. Students are bound by College policies, including AA 34 - Copyright, and SA 07 - Student Code of Conduct, and any student found to be using or posting course materials for public dissemination without permission is in breach of these policies and may be sanctioned.  Need HELP?? If you need help: 1. Email me for an appointment – can meet individually or as a group 2. Chat with me after or before class Email responses follow the AC policy – 48h grace (not including weekends and holidays) Expect email responses from me during regular College business hours with some exceptions. Ø After the 48h, please send me a polite reminder. J Dr. Pasan Fernando 3  How is acidity controlled? Henderson-Hasselbalch (HH) equation Acid base balance in practice Dr. Pasan Fernando  Mechanisms to control free H+ (pH) Chemical buffer regulation Brain stem regulation Renal regulation Bicarbonate buffering Central chemoreceptors Important in plasma Eliminates acids Sense carbon dioxide Regulates and maintains Major reactive centre reserve quantities of Phosphate buffering bicarbonate (alkaline reserve) Important in kidneys Peripheral chemoreceptors (buffers urine) carotid and aortic bodies Sense carbon dioxide Dr. Pasan Fernando Protective centre Protein buffering Important in cells 5  Chemical Buffer Systems Chemical buffer is a system of one or more compounds that act to resist pH changes when strong acid or base is added Will bind H+ if pH drops or release H+ if pH rises Three major chemical buffering systems: Bicarbonate buffer system Phosphate buffer system Protein buffer system Dr. Pasan Fernando 6  Determine the acid-based status Patient A – blood gas assay: pH 7.49 HCO3- = 36 mmol/L pCO2 = 48 mmHg Write out the HH equation for each of the following conditions: metabolic acidosis/metabolic alkalosis/respiratory acidosis/respiratory alkalosis Indicate which variable in the HH equation is responds to compensate for each of the four conditions Draw out the HH equation for patient A Determine the acid-base status by comparing patient A to the four conditions. Dr. Pasan Fernando Is there compensation or no compensation? à determine if the variable that responds is within or outside the normal ranges of HCO3- and pCO2 7  Lecture 2 Cardiovascular System – The Heart 1. Describe the shape, location and orientation of the heart in the thoracic chamber. 2. Name the coverings of the heart and the three layers of the heart wall. 3. Describe the functions of the four heart chambers, their associated heart valves and their mechanism of operation. 4. Trace the pathway of blood flow through the heart 5. Name and describe the major branches of the coronary vessels 6. Describe the structural and functional properties of cardiac muscle and compare with skeletal muscle Dr. Pasan Fernando 8  At an average 70 beats/min: § Heart contracts AND relaxes more than 100 000 times/day Ø Without stopping Ø Without tiring Ø Without complaining (most of the time)… § Rate and strength will change to meet the normal physiological demands AND the pathological challenges of the body § The heart is a highly adaptable organ Dr. Pasan Fernando 9  Capillary beds Heart Anatomy of lungs where gas exchange occurs Pulmonary Circuit The Pulmonary and Systemic Circuits Pulmonary arteries Pulmonary veins Heart is a transport system consisting of two Aorta and side-by-side pumps Venae branches cavae § Right side receives oxygen-poor blood from tissues Left atrium Ø Pumps blood to lungs to get rid of CO2, pick up O2, Left via pulmonary circuit Right ventricle § Left side receives oxygenated blood from lungs atrium Right Heart ventricle Ø Pumps blood to body tissues via systemic circuit Systemic Circuit Dr. Pasan Fernando Capillary beds Oxygen-rich, of all body CO2-poor blood tissues where gas Oxygen-poor, exchange occurs CO2-rich blood 10  Capillary beds Four Chambers of the Heart of lungs where gas exchange occurs Pulmonary Circuit Receiving chambers of heart Pulmonary Pulmonary § Right atrium arteries veins Ø Receives blood returning from systemic circuit Aorta and Venae branches § Left atrium cavae Left Ø Receives blood returning from pulmonary atrium circuit Left Right ventricle Pumping chambers of heart atrium Right Heart ventricle § Right ventricle Systemic Circuit Ø Pumps blood through pulmonary circuit § Left ventricle Ø Pumps blood through systemic circuit Dr. Pasan Fernando Capillary beds Oxygen-rich, of all body CO2-poor blood tissues where gas Oxygen-poor, exchange occurs CO2-rich blood 11  The Heart Is Located In The Mediastinum Approximately the size of a fist § Weighs less than 1 pound Midsternal line Location 2nd rib § In mediastinum between second rib and fifth intercostal space Sternum § On superior surface of diaphragm Diaphragm Location of § Two-thirds of heart to left of apical midsternal line impulse § Anterior to vertebral column, posterior to sternum Dr. Pasan Fernando àpalpate the apical impulse of your heart 12  Pulse points are not the same as apical pulses palpated in the mediastinum § Body pulses are palpated on a superficial artery § Body pulses are generated by pressure in the arterial vasculature Dr. Pasan Fernando 13  The Mediastinum § The mediastinum is an anatomical region within the thoracic cavity § Mediastinum L. midway § The space within the mediastinum consists of organs, nerves, blood vessels and connective tissue § Three regions within the mediastinum in relation to the heart include: Ø Superior, anterior, and posterior mediastinum Ø The heart and pericardium lie in the middle region Dr. Pasan Fernando 14  Descending aorta Tissue of mediastinum Esophagus Bronchus of lung Right pleural cavity Parietal pleura Right lung Left pleural cavity Visceral pleura Right atrium Right ventricle Left atrium Left ventricle Visceral pericardium Visceral pericardium Pericardial cavity Pericardial cavity Dr. Pasan Fernando Parietal pericardium Parietal pericardium Fibrous pericardium Superior view Fibrous pericardium 15  Coverings of the Heart Pulmonary trunk Fibrous pericardium Parietal layer of serous Pericardium pericardium Myocardium Pericardial cavity Epicardium (visceral layer of serous pericardium) Heart wall Myocardium Endocardium Dr. Pasan Fernando Heart chamber 16  Dr. Pasan Fernando 17  Coverings of the Heart Pericardium § Double walled sac, surrounds heart to make two layers. 1. Superficial fibrous pericardium Ø Protection Ø Anchors heart to surrounding structures, prevents overfilling 2. Deep two-layered serous pericardium Ø Parietal layer Dr. Pasan Fernando Ø Visceral layer 18  Clinical – Homeostatic Imbalance Pericarditis § Inflammation of pericardium § Roughens membrane surfaces, causing pericardial friction rub (creaking sound) heard with stethoscope Cardiac tamponade Ø Excess fluid that leaks into pericardial space Ø Can compress heart’s pumping ability Ø Treatment: fluid is drawn out of Dr. Pasan Fernando cavity (usually with syringe) 19  Pericardial Friction Rub Auscultate § Patient is in upright sitting position § Patient holds breath on expiration § Listen for high pitched scratching or crunching sound in a high-low wave like pattern Dr. Pasan Fernando 20  Layers of the Heart Wall Heart wall has three layers 1. Epicardium: visceral layer of serous pericardium 2. Myocardium: circular or spiral bundles of contractile cardiac muscle cells Cardiac Cardiac skeleton: crisscrossing, interlacing muscle layer of connective tissue bundles Anchors cardiac muscle fibers Supports great vessels and valves Limits spread of action potentials to specific paths 3. Endocardium: innermost layer; is continuous Dr. Pasan Fernando with endothelial lining of blood vessels Ø Lines heart chambers and covers cardiac skeleton of valves 21  The Cardiac Skeleton Cardiac skeleton § Fibrous, collagen-based connective tissue § Four rings that surround and support each of the four valves § Extends and attaches with the interventricular septum § Allows the controlled contraction of the heart (atria à ventricles) Dr. Pasan Fernando 22 https://www.liverpool.ac.uk/~trh/local_html/heartdisease/fibrous_cardiac_skeleton.htm  Functions of the Cardiac Skeleton § Cardiac skeleton is connection of dense connective tissue § Attaches to atrial and ventricular myocardium § Supports and reinforces the function of four valves § Electrically separates/insulates atria and ventricles Dr. Pasan Fernando 23  Chambers and Associated Partitions Internal features § Four chambers Ø Two superior atria Ø Two inferior ventricles § Interatrial septum: separates atria § Interventricular septum: separates ventricles Dr. Pasan Fernando 24  The Pensive Paramedic True or False…….. The heart is all about that base. Dr. Pasan Fernando 25  Heart – Anatomical Features Aorta Left pulmonary artery Superior vena cava Left atrium Right pulmonary artery Left pulmonary veins Pulmonary trunk Right atrium Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Right ventricle Left ventricle Chordae tendineae Papillary muscle Interventricular septum Trabeculae carneae Epicardium Dr. Pasan Fernando Inferior vena cava Myocardium Endocardium Frontal section 26  Heart – Anatomical Features Surface features Brachiocephalic trunk Left common carotid artery Left subclavian artery § Demarcate boundaries of four chambers Superior vena cava Aortic arch Ligamentum arteriosum Ø Coronary sulcus (atrioventricular Right pulmonary artery Left pulmonary artery Ascending aorta groove) Pulmonary trunk Left pulmonary veins – Encircles junction of atria and Auricle of left atrium ventricles Right pulmonary veins Circumflex artery Ø Anterior interventricular sulcus Right atrium Right coronary artery Left coronary artery – Anterior position of interventricular (in coronary sulcus) (in coronary sulcus) Anterior cardiac vein Left ventricle septum; between left and right Right ventricle ventricles Right marginal artery Great cardiac vein – Continues to posterior IVS Small cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Dr. Pasan Fernando Inferior vena cava Ø Posterior interventricular sulcus Apex Anterior view – Landmark on posteroinferior surface 27  Dr. Pasan Fernando 28  Aorta Superior vena cava Right pulmonary artery Left pulmonary artery Right pulmonary veins Left pulmonary veins Auricle of left atrium Right atrium Left atrium Inferior vena cava Great cardiac vein Coronary sinus Posterior vein of Right coronary artery left ventricle (in coronary sulcus) Posterior interventricular Left ventricle artery (in posterior interventricular sulcus) Dr. Pasan Fernando Middle cardiac vein Right ventricle Apex Posterior surface view 29  Atria Aorta Su Atria: the receiving chambers Left pulmonary artery Ri § Small, thin-walled chambers; contribute little Ri Left pulmonary veins to propulsion of blood Auricle of left atrium Ri § Auricles: appendages that increase atrial Left atrium volume Inf § Right atrium: receives deoxygenated blood Great cardiac vein Co from body Posterior vein of Ri Ø Anterior portion is smooth-walled left ventricle (in Po Left ventricle ar int Mi Dr. Pasan Fernando Ri Apex Posterior surface view 30  Atria Atria (cont.) Aorta Superior vena cava Ø Three veins empty into right atrium: Right pulmonary artery Left pulmonary artery – Superior vena cava: returns blood Right pulmonary veins from body regions Left above the veins pulmonary diaphragm Right atrium Auricle of left atrium – Inferior vena cava: returns blood Left atrium from body regions below the Inferior vena cava diaphragm Great cardiac vein Coronary sinus – Coronary sinus: returns blood Posterior vein of Right coronary artery from coronary veinsleft(visible ventricle on (in coronary sulcus) posterior surface) Posterior interventricular § Left atrium: receives oxygenated Left ventricle artery (in posterior interventricular sulcus) Dr. Pasan Fernando blood from lungs Middle cardiac vein Ø Four pulmonary veins return blood from lungs Right ventricle Apex 31 Posterior surface view  Ventricles Ventricles: the discharging chambers § Make up most of the volume of heart § Right ventricle: occupies most of anterior surface § Left ventricle: occupies posterior-inferior surface § Papillary muscles: project into ventricular cavity Ø Anchor chordae tendineae that are attached to heart valves Dr. Pasan Fernando 32  Atrioventricular valves Two atrioventricular (AV) valves prevent backflow into atria when ventricles contract § Tricuspid valve (right AV valve): made up of three cusps and lies between right atria and ventricle § Mitral valve (left AV valve, bicuspid valve): made up of two cusps and lies between left atria and ventricle § Chordae tendineae: anchor cusps of AV valves to papillary muscles that function to: Ø Hold valve flaps in closed position Ø Prevent flaps from everting back into atria Dr. Pasan Fernando 33  Atrioventricular valves Right Left atrium atrium Tricuspid valve Chordae Mitral valve tendineae Myocardium Myocardium of left of right ventricle ventricle Papillary Interventricular muscles Chordae tendineae Papillary septum attached to tricuspid muscle Dr. Pasan Fernando valve flap 34  Atrioventricular Valves § Valves DO NOT open/close by electrical stimulus § Rely on differential pressure within the cardiac chambers 1 Blood returning to the Direction of heart fills atria, pressing blood flow against the AV valves. The increased pressure forces Atrium AV valves open. Cusp of 2 As ventricles fill, AV valve atrioventricular flaps hang limply into ventricles. valve (open) Chordae tendineae 3 Atria contract, forcing additional blood into ventricles. Papillary Dr. Pasan Fernando Ventricle muscle AV valves open; atrial pressure greater than ventricular pressure 35  Pulmonary valve Aortic valve Area of cutaway Semilunar ValvesMitral valve Tricuspid valve Two semilunar (SL) valves Myocardium prevent backflow from major arteries back into ventricles Mitral (left atrioventricular) § Open and close in response to pressure valve changes Tricuspid § Each valve consists of three cusps that (right atrioventricular) roughly resemble a half moon valve § Pulmonary semilunar valve: located Aortic between right ventricle and pulmonary valve trunk Pulmonary § Aortic semilunar valve: located valve between left ventricle and aorta Cardiac Dr. Pasan Fernando skeleton Anterior 36  Aorta Pulmonary trunk As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. Dr. Pasan Fernando Semilunar valves open 37  Pathway of Blood Through the Heart § Equal volumes of blood are pumped to pulmonary and systemic circuits § Pulmonary circuit is short, low-pressure circulation § Systemic circuit is long, high-friction circulation § Anatomy of ventricles reflects differences Left Right ventricle Ø Left ventricle walls are 3x thicker than ventricle right – Pumps with greater pressure Interventricular septum Dr. Pasan Fernando 38  Coronary Circulation - Arteries Aorta Pulmonary Superior trunk § Both left and right coronary arteries arise vena cava from base of aorta and supply arterial Left atrium blood to heart Anastomosis (junction of § Both encircle heart in coronary sulcus vessels) Left coronary § Branching of coronary arteries varies Right artery among individuals atrium Circumflex § Arteries contain many anastomoses artery Right (junctions) an-ass-toe-moe-sees coronary artery Left Ø Provide additional routes for blood ventricle delivery Right ventricle Anterior Ø Cannot compensate for coronary artery Right interventricular Dr. Pasan Fernando occlusion marginal artery § Heart receives 1/20th of body’s blood artery Posterior supply interventricular artery 39  Coronary Circulation - Arteries Aorta Pulmonary Superior Coronary arteries – main branches vena cava trunk § Left coronary artery supplies Left atrium Anastomosis interventricular septum, anterior ventricular (junction of walls, left atrium, and posterior wall of left vessels) Left coronary ventricle; has two branches: artery Right Ø Anterior interventricular artery atrium Circumflex Ø Circumflex artery artery Right § Right coronary artery supplies right atrium coronary artery Left and most of right ventricle; has two branches: ventricle Right Ø Right marginal artery ventricle Anterior Ø Posterior interventricular artery interventricular Right Dr. Pasan Fernando marginal artery artery Posterior interventricular artery 40  Coronary Circulation - Veins Coronary veins § Cardiac veins collect blood from capillary beds Superior vena cava § Coronary sinus empties into right atrium; formed by merging cardiac veins Ø Great cardiac vein of anterior Great Anterior cardiac interventricular sulcus vein cardiac Ø Middle cardiac vein in posterior veins interventricular sulcus Coronary sinus Ø Small cardiac vein from inferior margin § Several anterior cardiac veins empty directly into right atrium anteriorly Dr. Pasan Fernando Small Middle cardiac cardiac vein vein 41  Cardiac Muscle Cells – Intercalated Discs Intercalated discs are connecting junctions between cardiac cells that contain: § Desmosomes: hold cells together; prevent cells from separating during contraction § Gap junctions: allow ions to pass from cell to cell; electrically couple adjacent cells Ø Allows heart to be a functional syncytium, a single coordinated unit Cardiac Intercalated Gap junctions (electrically Desmosomes (keep muscle cell Nucleus discs connect myocytes) myocytes from pulling apart) Dr. Pasan Fernando 42  Cardiac Muscle Cell Cardiac muscle cell Mitochondrion Nucleus Intercalated disc Mitochondrion T tubule Sarcoplasmic Z disc reticulum Nucleus Dr. Pasan Fernando Sarcolemma I band A band I band 43  Cardiac Muscle vs Skeletal Muscle Differences between cardiac and skeletal muscle § Some cardiac muscle cells are self-excitable Ø Two kinds of myocytes – Contractile cells: responsible for contraction – Pacemaker cells: noncontractile cells that spontaneously depolarize » Initiate depolarization of entire heart » Do not need nervous system stimulation, in contrast to skeletal muscle fibers Dr. Pasan Fernando 44  Cardiac Muscle vs Skeletal Muscle § Heart contracts as a unit Ø All cardiomyocytes contract as unit (functional syncytium), or none contract Ø Contraction of all cardiac myocytes ensures effective pumping action Ø Skeletal muscles contract independently § Influx of Ca2+ from extracellular fluid triggers Ca2+ release from SR Ø Depolarization opens slow Ca2+ channels in sarcolemma, allowing Ca2+ to enter cell Ø Extracellular Ca2+ then causes SR to release its intracellular Ca2+ Dr. Pasan Fernando Ø Skeletal muscles do not use extracellular Ca2+ 45  Cardiac Muscle vs Skeletal Muscle § Tetanic contractions cannot occur in cardiac muscles Ø Cardiac muscle fibers have longer absolute refractory period than skeletal muscle fibers – Absolute refractory period is almost as long as contraction itself – Prevents tetanic contractions – Allows heart to relax and fill as needed to be an efficient pump Dr. Pasan Fernando 46  Cardiac Muscle vs Skeletal Muscle § The heart relies almost exclusively on aerobic respiration Ø Cardiac muscle has more mitochondria than skeletal muscle so has greater dependence on oxygen – Cannot function without oxygen Ø Skeletal muscle can go through fermentation when oxygen not present Ø Both types of tissues can use other fuel sources – Cardiac is more adaptable to other fuels, including lactic acid, but must have oxygen Dr. Pasan Fernando 47  Dr. Pasan Fernando 48 Skeletal muscle Cardiac muscle Not as many cell types; fewer Many cells types: specialized, cardio, specialized cells neural, immune, vascular, hematopoietic etc. multinucleated Single nucleated (humans) Fused fibers Single fibers Aerobic, anaerobic metabolism Aerobic metabolism Greater regenerative capacity Limited repair capacity Larger progenitor stem cell population Small progenitor stem cell population Grows by cell expansion and cell Grows in size by cell expansion number 49  Compare skeletal and cardiac muscle: structure, membranes, major proteins, metabolism, contraction, response to stress. Describe the protective features found on the surface of the heart that ensure its function. Describe the cardiac skeleton. How does it contribute to the concept of the cardiac syncytium? Dr. Pasan Fernando 50