Cardiovascular System 2 14 2020 1 4 heart chambers a Right atrium i Receives deoxygenated blood from 3 veins 1 Superior vena cava a Superior to diaphragm 2 Inferior vena cava a Inferior to diaphragm 3 Coronary sinus b Left atrium i Receives oxygenated blood from 4 pulmonary veins lungs 1 2 right pulmonary veins 2 2 left pulmonary veins 3 ALL VEINS CARRY BLOOD TO THE HEART c Veins usually deliver deoxygenated blood to the heart except in the case of pulmonary veins d Right ventricle 1 e Left ventricle Receives deoxygenated blood from right atrium Pumps deoxygenated blood through pulmonary trunk to lungs Left and right pulmonary arteries Receives oxygenated blood from left atrium Pumps oxygenated blood through aorta to tissues f Right atrium right ventricle left atrium left ventricle 2 Heart valves ensure unidirectional blood flow through the heart a Open and close in response to pressure changes b Blood flow Superior vena cava and inferior vena cava right atrium tricuspid valve right ventricle pulmonary valve pulmonary artery lungs left atrium left ventricle aorta rest of the body c Two major types of valve i ii i ii i i Atrioventricular valves located between the atria and ventricles try before you buy Functions 1 a When open allows blood to flow from atria to ventricles b When closed prevents backflow into atria when ventricles contract 2 Right tricuspid valve right ventricle a Made up of three cusps and lies between right atria and i Cusps flaps of endocardium supported by connective tissue 3 Left bicuspid valve or mitral valve a Made up of two cusps and lies between left atria and ventricle ii Semilunar valves located between the ventricles and major arteries 1 Right pulmonary valve a Between right ventricle and pulmonary arteries 2 Left aortic valve a Between left ventricle and aorta 3 Each valve consists of three cusps that resemble half moons They prevent backflow from major arteries back into ventricles a 4 Ventricular contraction valves open 5 Ventricular relaxation blood flows back from arteries fills cusps forcing them to close 3 Pressure and blood flow through the heart a Pressure dictates blood flow i Blood enters atria 1 Right atrium superior inferior vena cava 2 Left atrium pulmonary veins ii Increased blood therefore increased pressure in atria causes AV valves to open 1 Blood passes through open atrioventricular valves into ventricles iii iv Atria contract pushing additional blood into ventricles Ventricles contract 1 2 3 Pressure increases Forces atrioventricular valves to close Increased pressure opens the semilunar valves a Blood forced out of pulmonary arteries and aorta v Ventricles relax Pressure falls in ventricles 1 2 Blood moves back towards ventricles a b Fills cusps Filled cusps then close i Semilunar valves close c Blood propelled to lungs or systemic circulation 4 Cardiac muscle microscopic anatomy a myocardium b Intercalated discs are connecting junctions between cardiac cells that contain Desmosomes keeps cells together during contraction 1 Keep myocytes from pulling apart Gap junctions allows ions to pass from cell to cell electrically couple adjacent cells Electrically connect myocytes 1 2 Allows heart to be a functional syncytium a single coordinated c Myofibrils with thin actin and thick myosin filaments arranged in unit sarcomeres T tubules invagination of sarcolemma at Z discs SR lacks terminal cisternae SO NO TRIAD TC T tubule TC d 2 types of cardiac muscle cells Contractile cells muscle fibers responsible for heart pumping 1 Make up 99 of cardiac cells Autorhythmic cell self excitable cells that generate their own action potentials APs Pacemaker cell i ii i ii i ii iii iv 1 of cardiac cells 5 Action potentials a Action potential a brief change in the membrane potential charge across the membrane due to influx and efflux of ions b Depolarization cell becomes more positive due to influx of ions c Repolarization cell becomes more negative due to efflux of ions i Membrane potential returns to resting 6 Intrinsic conduction system a Pacemaker cells i Spontaneously depolarize b Sequence of excitation Sinoatrial node i Pacemaker of heart 1 2 Located in the right atrial wall ii Atrioventricular node 1 Receives impulse from sinoatrial node 2 Delay for 1 seconds a Allows atria to fully contract b Can act as a pacemaker in absence of sinoatrial node iii Atrioventricular bundle 1 Bundle of his a Conducts impulses from atria to ventricles b Divides into left right branches c Sends signals to apex of the heart iv v Right and left bundle branches Purkinje fibers 1 Subendocardial conducting network a Go through apex and move towards base b Allow ventricles to contract