Physiology
Physics Of Blood Flow
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Get accessVelocity is inversely proportional to the cross-sectional area at that point in a system of tubes
Eg. velocity is higher in the aorta than in capillaries (which in total have a much larger cross-sectional area)
- Resistance is
- Inversely proportional to the radius of the vessel to the fourth power
- Directly proportional to the length of the vessel
- Directly proportional to the pressure gradient along the vessel
- Dependent on the viscosity of blood (ie. haematocrit)
- Blood pressure = cardiac output x peripheral resistance
- Cardiac output = heart rate x stroke volume
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Starling’s Law: force of contraction proportional to the initial length of the muscle
- Increased preload will increase myocardial stretch and increase stroke volume
- Afterload initially causes reduced stroke volume due to increased resistance