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Factors Controlling Stroke Volume
Left Atrial Pressure: 10
Ventricular Function Plot
Contractility is the inherent strength and vigour of the heart's contraction during systole.
According to Starling's Law, the heart will eject a greater stroke volume at greater filling pressures. For any filling pressure (LAP), the stroke volume will be greater if the contractility of the heart is greater.
The inherent strength and vigour of the heart's contraction during systole may be increased by sympathetic autonomic activity and by pharmacologic agents.
- Sympathetic Activity: Physical exertion and emotional experience such as fear and anger produce an increase in sympathetic activity which releases noradrenalin from nerve terminals in the heart.
- Pharmacologic agents: Drugs which increase cardiac contractility are called positive inotropic agents. Examples of these are dopamine, adrenalin and digoxin.