Control of Cardiac Output Flashcards
cardiac output
Stroke volume x heart rate
Intrinsic mechanisms that control stroke volume
– Self-regulation
– Frank-Starling mechanism
– ↑EDV↑ force of contraction
Preload
– Venous pressure and venous return to heart (end diastolic pressure, EDP)
Afterload
– Aortic/pulmonary artery pressure
Extrinsic mechanisms that control cardiac output
– Sympathetic nerves
Frank-Starling’s Law of the Heart
Allows for automatic adjustment for small imbalances between the left ventricle and right ventricle.
- Automatic balancing between CO from left-side of heart to volume returning to right-side.
Pressure in the systemic and pulmonary vessels
small occelations in the left atrium
large occelations in the left ventricle which decreases from the Aorta to the arterioles then in the capillaries there is none in the capillaries
Vascular compliance
compliance decreases with age and vasoconstriction
Non-compliant:
rigid tubes resist expansion when internal pressure rises
capillaries, arterioles etc.
Compliant:
tubes with elastic walls swell when internal pressure rises etc. arteries, veins
Mean arterial blood pressure (MABP)
Diastolic pressure + 1/3 pulse pressure
Pulse pressure
systolic pressure – diastolic pressure
Factors determining the magnitude of pulse pressure
Stroke volume
Speed of ejection of stroke volume
Arterial compliance
Stroke volume
– Intrinsic and extrinsic factors
– Remember afterload, preload, sympathetic
innervation
Arterial compliance
– Decreases with age
• Arteriosclerosis
