PHGY 214 Lecture Notes - Lecture 29: Vasoconstriction, Staling, Aorta
9 Dec 2017
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Sv: amount of blood ejected from either ventricle during 1 heart beat sv= edv-esv. Heart rate: # of beats per minute (# of ap our sa node fires per min) Para fibers project via vagus nerve to sa and av node, post gang release ach which decreases hr (dn control purkinje or bundle of his) sympathetic stimulation. Sa node depol controlled by l-type ca chan so spread of depol is faster. At rest para tone predominates (keeps hr low), sa node under tonic influence of autonomic ns. Frank starling law: heart intrinsically adapts to alt in venous return. More venous return (edv increases) leads to increase in sv due to ability to adapt to alt in venous return. Heart/ myocardial cells stretch causes greater force of contraction. Preload: the extend of filling, work imposed on the heart prior to systole (ex. Afterload: force of ventricle wall necessary to pump blood (work imposed on heart after contraction has begun)
