cardiovascular - lecture 3 Flashcards
how do you calculate stroke volume?
EDV (end diastolic volume) - ESV (end systolic volume)
how do you calculate cardiac output?
heart rate x stroke volume
what is the average stroke volume?
135 ml (EDV) - 65 (ESV) = 70ml
how do you calculate the ejection fraction?
stroke volume (EDV - ESV) / EDV
what is the normal ejection fraction?
normally 50-70, can get up to 90 with exercise
what impacts cardiac output?
stroke volume and heart rate
what factors impact heart rate?
parasympathetic innervation decreases
sympathetic innervation and epinephrine increases
what factors impact stroke volume?
extrinsic control - sympathetic innervation and epinephrine impacts contractibility and venous constriction
intrinsic control - skeletal muscle pump and respiratory pump impact venous return which impacts end diastolic volume
where are sympathetic neurons?
innervate SA node and AV node to richly innervate ventricle
where are parasympathetic neurons?
innervate SA node and AV node to sparsely innervate ventricle
where is the cardiovascular control centre?
in the medulla oblongata
how does the parasympathetic system affect heart rate?
muscarinic receptors of auto-rhythmic cells increase K+ efflux and decrease Ca2+ influx to hyper polarize cell and decrease rate of depolarization
how does the sympathetic system affect heart rate?
b receptors of auto-rhythmic cells increase Na+ and Ca2+ influx to increase the rate of depolarization
what is the Frank-Starling law?
force generated by cardiac muscles in proportional to the initial length of cardiac muscle fibres (stroke volume increases with increase in EDV)
what is preload?
workload imposed on cardiac muscle BEFORE the heart begins to contract
what is contractability?
ability of the muscle to contract and generate force
what do catecholines do?
accelerate both contraction (increase movement of Ca2+ into cell) and relaxation (increase phosphorylation of phospholamban and troponin)
what is afterload?
workload imposed on cardiac muscles after the contraction has begun
what affect do afterload and preload have on stroke volume?
afterload decreases stroke volume, preload reduces it
what affect does contractability have on stroke volume?
contractibility increases stroke volume
how does the heart produce energy?
fatty acid oxidation
