Lecture 11

CREATEDATE 11/7/09 1:55 PM Cardiovascular System- Lecture 11 3 basic components Heart Blood vessels Blood 2 Vascular loops systemic loop- carries blood between heart and other body systems pulmonary loop- carries blood between heart and lungs Heart - Positioning lies in thoracic cavity between sternum and vertebrae position makes it physically possible to manually drive blood prom heart when it isn?t working (CPR) -Anatomy pericardial sac: encloses heart has a tough, fibrous covering anchors heart so it remains properly positioned and has a secretory lining secretes pericardial fluid which provides lubrication to prevent friction between pericardial layers during heart beats pericarditis is inflammation of pericardial sac Heart wall Endocardium: thin, inner, epithelial tissue ( lines entine circulatory system Myocardium: middle layer, made of cardiac muscle Epicardium: thin external layer that covers heart Atria: upper chambers of heart, receive blood Ventricles: lower chambers of heart, pump blood Left ventricle has thicker myocardium due to hypertrophy that comes from the force with which it is required to contract Septum: separates right and left halves of heart, and prevents mixture of blood Venae Cavae: 2 large veins that return blood to right atrium Pulmonary Artery: carries blood from right ventricle to lungs Has 2 branches each going to 1 lung Pulmonary Veins: carry oxygenated blood from lungs to left atrium Aorta: Large artery that carries blood away from left ventricle Atrioventricular Valves (AV valves): between atrium and ventricle on right and left sides Prevent blood backflow into atria from ventricle during ventricular pump Tricuspid Valve: right AV valve Bicuspid/ Mitral Valve: left AV valve Chordae tendineae: though, fibrous cords that fasten edges of AV valve leaflets and prevent valves from being opened in opposite direction or turned inside out Attach to papillary muscles ( protrude from walls of inner ventricle Semilunar Valves Aortic valve: lie where aorta leaves ventricle Pulmonary valve: lies where pulmonary artery leaves ventricle **there are no valves between veins and atria because atrial pressure isnt?t much more than venous pressure and venae cavae sites are partially compressed during atrial contraction Myocardium: cardiac muscle fibers (cells) Intrinsic rhythmicity (highest = SA Node) Highly conductive Propagate electrical activity One or two centrally located nuclei Lots of mitochondria (40% in comparison 2-3% skeletal) Are involuntary cells Intercalated disks: connect cardiac muscle cells; 2 types membrane junction Desmosomes- mechanically holds cells together Gap junctions- areas of low electrical resistance; allow passage of AP from one cell to next Synctium: muscle cells connected by continuous cytoplasmic bridges, contract as single Skeletal Muscle Vs. Cardiac Muscle Electrical Activity of Heart Autorhythmicity: heart beats by action potentials it generates 2 types of cardiac cells contractile: 99% and do mechanical work autorhythmic: don?t contract, but initiate conduction potentials (pacemaker cells) AP generated spontaneously as membrane potential drifts to threshold (pacemaker potential( unstable resting membrane potential) Leaky cell membranes Funny channels that open Na+ when cell potential is negative, close K+, and open Ca+ ( constant depolarization Membrane channels permeable to both Na+ and K+ -At resting potential (-60) funny channels permit entry of Na+ and prohibit exit of K+ ( gradual depolarization ( T-type Ca+ channels open ( threshold reached ( L-type Ca+ channels open = rising phase of AP ( K+ leaving cell causes falling phase ( constant polarization and depolarization -Atria contract( brief delay ( ventricular contraction -Contractile Cells contractile cells experience prolonged positive phase of AP ( followed by prolonged contraction (plateau) due to slow activation of L-type Ca+ channels similar to skeletal muscles resting membrane potential -90 Noncontractile cardiac cells are found in SA node: region in right atrial wall near opening of superior vena cava Pacemaker of heart that establishes heart rate AV node: base of right atrium, near septum Bundle of His: originates in AV node and enters interventricular septum ( right and left branches alond ventricular walls Purkinje fibers: extend from bundle of His into ventricular myocardium Components of EKG Waves Segments Intervals- wave segment combinations Heart Sounds