During ventricular filling the cardiac muscle fibers are stretched pulling the

During ventricular filling the cardiac muscle fibers

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During ventricular filling, the cardiac muscle fibers are stretched pulling the myofilaments closer together—allowing more cross-bridge interactions once Ca 2+ pulls the troponin-tropomyosin complex away from actin’s cross-bridge binding sites. Thus, the length-tension relationship in cardiac muscle depends NOT on muscle fiber length per se but on the resultant variations in the lateral spacing between actin & myosin filaments. ° Coronary Blood Flow: Nutrient supply to the heart itself Cardiac muscle receives most ( 70%)of its blood during cardiac diastole o Diastole= relaxation During systole: o Systole= contraction o Compression of major branches of coronary arteries o Open aortic valve partially blocks the entrance to the coronary vessels Partially blocks adequate supply of blood to the heart at the moment Coronary blood flow adjusts to changes in the heart’s oxygen requirements; high metabolic activity releases more adenosine (from breakdown of ATP) which causes dilation of coronary blood vessels. Anaerobic metabolism very limited—cardiac muscle depends on oxygen Cardiac muscle fuel sources : free fatty acids >> glucose & lactate ° Figure 9-31: Extent of myocardial damage as a function of the size of the occluded vessel.
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o P wave= atrial depolarization o PR segment= AV node delay o QRS Complex= ventricular depolarization, atria repolarizing (simultaneously) o ST segment= time during which ventricles are contracting and emptying o T wave= ventricular repolarization o TP interval= time during which ventricles are relaxing and filling ° ° ° °
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Chapter 10 Blood Vessels and Blood Pressure ° Figure 10.4: Basic organization of the cardiovascular system ° ° Two Systems: pulmonary circulation & systemic circulation Artery: blood from heart organs o Heart Artery arteriole capillary o *capillaries rejoin to form venules Veins: blood leaves organ heart o Capillary venule vein heart Arteries progressively branch as they carry blood from the heart to the organs. A separate small arterial branch delivers blood to each of the various organs.
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