1. Prof. Ashraf Husain

7.  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 7

8. 8  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.