Prof. Ashraf Husain

Minus

Cardiac Output

Stroke Volume Heart Rate

End diastolic volume (EDV)

Venous return (Preload)

End Systolic volume (ESV)

Contractility After Load (Aortic pressure)

Isotonic Contraction

(Starling Law)

Isovolumetric

Contraction

-ve inotropic effect

+ve inotropic effect

Positive ionotropic effect. Sympathetic stimulation Adrenaline & Noradrenaline Calcium ion Caffine Drugs eg. Digitalis (Digoxin)

Negative ionotropic effect Parasympathetic stimulation Acetyl choline Potassium ion Hypoxia (Decrease oxygen) Acidosis Bacterial toxin Drugs eg. Calcium channel blockers, β- Blockers

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Within physiological limits, if there is increase in initial length of cardiac muscle fiber ( due to increase venous return) there will be increased strength of contraction.

Reason:Because Actin & Myosin filaments are

brought to more optimal degree of sliding therefore increase force of contraction

Note: starling’s law affects cardiac contractility but details you will learn with Cardiac out put .