Chapter 9 Part 1 Cardiac physiology Learning objectives 05 31 2013 Compare and contrast the left and right side of the circulation What factors determine how a fluid flows through a tube Trace a drop of blood through the heart and list the structures in Describe spread of electrical excitation over the heart Be able to label an entire normal ECG and explain the various wave order that it flows by forms represent What kinds of heart pathologies can an ECG diagnose in general Be able to answer objective questions number 13 and 14 at the end of the chapter based on the cardiac cycle Be able to explain the left ventricular volume curve and aortic pressure curve in the cardiac cycle Include comments on heart sounds output Describe the extrinsic and intrinsic factors that control cardiac What is the sequence of events for atherosclerotic plaque formation and how can this lead to myocardial infarction Introduction principles Components of the circulatory system Heart o Develops pressure that imparts energy momentum to the blood thereby pushing the blood through the resistance of blood vessels All fluids move in tubes require a pressure difference between the ends of the tubes In the body this pressure difference is due to the mechanical action of the heart Blood vessels Tube like conduits that distribute blood to nearly every cell in the body ARTERIES AWAY FROM HEART VEINS TO THE HEART Components of the circulatory system Blood o The fluid medium that transports blood cells nutrients ions gases metabolic waste products hormones toxins bacteria viruses antibodies heat Above substances are either dissolved in blood e g ions gases or are suspended in the blood e g blood cells The heart is a 4 chambered dual pump The right side of the heart pumps approximately 5 liters min of blood to the pulmonary circulation while at the same time the left side of the heart is pumping 5 liters min of blood to the systemic circulation LEFT AND RIGHT CARDIAC OUTPUTS 5L MIN OF THE HEART ARE HOMEOSTATICALLY MAINTAINED TO BE EQUAL Arteries always convey blood away from the heart Veins always convey blood to the blood pulmonary circulation RIGHT SIDE OF HEART systemic circulation LEFT SIDE OF HEART Basic physics of fluid flowing in tubes o Fluid pressure is directly proportional to the energy and momentum contained within the tube The greater the energy and momentum the greater the fluid pressure o Fluids move through tubes ONLY IF THERE IS A PRESSURE DIFFERENCE BETWEEN THE TWO ENDS OF THE TUBE and if flow resistance is not excessive Fluid moves from high to low pressure Heart Gross Anatomy THICKINESS OF LEFT VENTRICULAR WALL IS GREATER BECAUSE OXYGENATED BLOOD MUST FLOW THROUGH THE AORTA changes in pressure across the heart valve will open or close the valve SYSTOLE CONTRACTION EMPTYING PHASE OF ATRIA OR VENTRICLES DIASTOLE RELAXATION FILLING PHASE OF ATRIA OR VENTRICLES N B typically when systole or diastole are stated without additional qualification the person is referring to ventricular systole and ventricular diastole rather than events in the atria NOTE 120 80 IS NORMAL BLOOD PRESSURE Heart valve anatomy Right side of the heart Right atroventricular valve a k a tricuspid Pulmonary semilunar valve Left Side of the Heart Left atrioventricular valve aka bicuspid mitral Aortic semilular valve VENTRICULAR DIASTOLE VENTRICULAR SYSTOLE ATROVENTRICULAR VALVES ARE OPEN PULMONARY SEMILUNAR VALVE AND AORTIC VALVE ARE OPEN Start of New material for Exam 3 Heart wall has 3 layers Epicardium o A thin outer layer of epithelial cells o Not involved in contraction o Secreting fluid that goes into pericardium sack Myocardium o Thick middle layer of striated cardiac muscle cells coronary blood vessels and autonomic nerve fibers Endocardium remember endocardium endothelium o A thin inner layer a little thicker than epicardium of endothelial cells o Directly contacts blood in heart chamber o Continues as endothelium of blood vessels Heart muscle is arranged in a spiral fashion that results in a wringing out motion during ventricular systole Cardiac muscle fibers have special cell cell junctions called intercalated disks o spot weld of adjacent plasma membrane that provides Desmosomes mechanical coupling gap junctions o allows ions to cross quickly from one cell to it neighbor thus transmitting changes in trans membrane potential as a consequence of this mechanical and electrical coupling of adjacent cardiac cells the entire heart acts as a functional o syncytium o i e when one cell changes its transmembrane potential the rest of the cells quickly follow suit o this provides a basis for a coordinated synchronous contraction of the heart as required to efficiently pump blood infer heart valve action but you are not listening to the heart valves themselves Auscultation accomplished by placing the stethoscope superficial to the chamber or vessel into which the blood has passed and basically in line with the axis of the valve orifice and bowel sounds Stethoscopes are used to auscultate heart sounds lung air flow A stethoscope amplifies mechanical vibrations resonating in the chest cavity due to blood being suddenly stopped when valves close A stethoscope does not technically hear the actual valve cusps touch just the effect of the valve closure o pulmonary valve aortic valve mitral valve ALL PHYSIANS TAKE MONEY tricuspid valve on right side of the heart Heart electrophysiology Myocardium o Thick layer middle layer o Composed of two cell types Cardiac muscle fibers Do not initiate their own action potentials Innervated by sympathetic nervous system only BINDS o Adrenergic receptors norepinephrine o Autonomic ganglia acetylcholine nicotinic receptors Comprise 99 of myocardium Do the MECHANICAL WORK of generating blood pressure Autorythmic pacemaker cells Comprise remaining 1 of myocardium Exhibit an intrinsic pacemaker activity spontaneously generate action potentials without enquiring any neural or hormonal inputs Determine heart rate Innervated by BOTH sympathetic and parasympathetic nervous system are highly modified cardiac muscle fibers that lost their contractile machinery so do not appear striated under a microscope thus do not contribute to developing blood make up nodes and fiber bundles of the Cardiac pressure Conduction System o Myosin filaments o Calcium trigger calcium Autorythmic cells keeps beat of the heart o No resting membrane potential Constantly depolarizing o slow depolarization phase pacemaker potential Na