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cardiac physiology Q5

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Questions and Answers

starlings law.

increase in blood returning to heart increases EDV which causes extra stretching which causes increase in the next contraction.

mechanism-starlings law.

increased stretch of ventricles result in overlap of actin and myosin filaments>more cross bridges > increases stretch increases the sensitivity of contractile proteins to Ca++> intra ca++ required to generate 50% max tension is now lower when muscle fibre is stretched.

how neural control of the heart is regulated?

through sympathetics and parasympathetics divisions of ANS in medulla oblongata.

what we call the effects of autonomic nervous system on the heart?

chronotrophic effects. Signup and view all the answers

whats positive chronotrophic effects?

increase in heart rate (sympathetic); norepinephrine is released from sympatshtcis nerve fibres> activate Beta1 receptors in the SA node> an increase in funny channels (Na+)> increase the rate of phase 4 depolrization and intra Ca++ channels>more action potential>increase heart rate. Signup and view all the answers

whats negative chronotrophic effects?

a decrease in heart rate- acetylcholine is released from parasympathetic nerve fibres>activate muscarinic receptors in the SA node Signup and view all the answers

what equation determines the BP?

BP= COSVR CO (cardiac output)=SVHR. SVR (systemic vascular resistance) the resistance the blood encounters as it moves through the (atrial system). Signup and view all the answers

systolic BP is determined by?

by SV (stroke volume) being ejected by the heart and the ability of aorta to stretch to accommodate SV. Signup and view all the answers

diastolic pressure is determined by?

the energy stored in the elasticity of fibres that are stretched during systole. Signup and view all the answers

elastic arteries r called Windkessel's vessels, why?

because of their abundant (elastic tissue) Signup and view all the answers

Flashcards

Starling's Law

Increased blood returning to the heart (EDV) stretches the ventricles, leading to a stronger heart contraction.

Mechanism of Starling's Law

Increased ventricle stretch leads to more actin-myosin overlap, more cross-bridges, and higher sensitivity to calcium, needing less calcium for a stronger contraction.