myocardiumthickest and middle layer of the heart wall that is composed of cardiac muscle tissue and a fibrous skeletonepicardiummost superficial layer of the heart wallRight atriumlarger, thinner-walled and more anterior than left atriumLeft atriumthicker walled, somewhat smaller and mostly on posterior side of heartright ventriclewider and thinner and pumps against less resistance (works less)left ventriclecircular in shape and has thicker walls and pumps against greater resistance (works harder)atrioventricular sulcussmall crevice between the atria and ventricles that contains the anterior interventricular artery, great cardiac vein, left coronary artery, and posterior interventricular arteryinterventricular sulcussmall crevice between the ventricles that contain that anterior interventricular artery, great cardiac vein, left coronary artery, and posterior interventricular arteryinteratrial septumthin wall that separates both atriainterventricular septummuscular wall between the ventriclespectinate musclesmuscular ridges on the anterior side of the internal surface of the right atriumtrabeculae carneaeirregular protrusions of cardiac muscles that create ridges that can be found in both ventriclespapillary musclesfinger-like projections of muscles in the ventricles that attach to the atrioventricular valveschordae tendinaetendon-like cords that attach the papillary muscles to the AV valvesatrioventricular valves (AV)valve between an atrium and ventricleright AV (tricuspid)valve between the right atrium and ventricleleft AV (bicuspid/ mitral)valve between the left atrium and ventricleSemilunar valveprevent blood from flowing back into ventriclespulmonary trunkbetween right ventricle and pulmonary trunkaortic valvebetween left ventricle and aortaS1 (lubb)occurs during closing of AV valves and is longer and louder than S2 and is created from the tricuspid and mitral valvesS2 (dupp)during closing of semilunar valves and is created from the aortic and pulmonary valvesVentricular filling phase (1)-ventricles fill with blood and are in diastole - AV valves are open -atrial systole occurs -semilunar valves are closed - EDV (end diastolic volume) is reached at the end of this phase - roughly 120ml and its the ventricular volume at the end of ventricular diastole - blood flows into the ventricles from the atria through the AV valvesIsovolumetric contraction phase (2)- ventricular systole begins - AV and SL valves close when pressure builds in ventricles - Atrial diastole begins - blood will continue to flow into the ventricles and AV valves closeVentricular ejection phase (3)- ventricular systole continues - AV valves are still close -Atrial diastole continues - pressure open SL valves and blood is ejected into the pulmonary artery and aorta - ESV - end systolic volume - the ventricular volume following ventricular systole (roughly 50ml)isovolumetric relaxation phase (4)- ventricular diastole begins - AV valves are still closed - Atrial diastole continues -SL valves close - blood will flow into the ventricles at the beginning of the next phase (ventricular filling phase)cardiac conduction system3 pacemaker cell populations that spontaneously generate action potentials and set the pace of the heart - SA node > AV node > AV bundle > bundle branches > Purkinje fibers`SA node (sinoatrial node)-upper right atrium -fastest rate of intrinsic depolarization (60+/minute)AV node (atrioventricular)- posterior and medial to the tricuspid valve - slower than SA node with intrinsic rate of depolarization (40/minute)Purkinje fiber system- slowest group that depolarizes only 20/minute - consists of AV bundle, Bundle branches, and Purkinje fibersAV bundlepenetrates the heart's fibrous skeleton in the inferior interatrial septum and the superior interventricular septumBundle branchescourse along the right and left side of the interventricular septum respectivelyPurkinje fibers (terminal branches)penetrate the ventricles and finally come into contact with the contractile cardiac muscle cellsSA node action potentials-no stable resting membrane potential - packemaker potential - slow influx of sodium ions -threshold -depolarization - rapid influx of calcium and sodium -repolarization - efflux of potassium ionscardiocyte action potentials-stable resting membrane potential -depolarization - rapid influx of sodium ions -plateau- influx of calcium - repolarization - efflux of potassiumelectrocardiogram- P wave - atrial depolarization - QRS complex - ventricular depolarization - T wave - ventricular repolarizationAtrial systoleoccurs during the ventricular filling phaseventricular systoleoccurs during the isovolumetric contraction phase and continues through the ventricular ejection phaseCardiac outputCO = SV * HRstroke volume (SV)amount of blood pumped out in one heartbeatPreloadblood in the heart before contraction - largely determined by EDV and the degree of stretch of the sarcomeres in the ventricular cellsFarnk-Sterling law of heartEDV is proportional to SV because the more blood in the heart before contraction the more blood will be ejectedafterloadresistance to blood being ejected from the ventricles - the force that the ventricles must overcome to eject blood into the respective arteriescontractilitystrength of contraction for a given periodESV and EDV are found in the ventricles during which cardiac cycleESV - isovolumetric relaxation phase (inversely related to SV) EDV - isovolumetric contraction phase (proportional to SV)Heart Ratedetermined by the rate at which the SA node generates action potentials