REGULATION OF ARTERIAL PRESSURE: BARORECEPTOR REFLEX
Regulating arterial pressure is necessary to maintain adequate perfusion of tissues.
Mean Arterial Pressure is affected in:
Anaphylaxis (serious allergic reaction – low BP, throat swelling).
Sepsis (whole body inflammation – increased HR).
Haemorrhage (bleeding from a leakage in a vessel).
Normal Arterial Pressure – 120/80 mmHg (millimetres of mercury).
1mmHg = 0.13kPa.
Hypertension = > 140/90 mmHg (regularly above this value but usually higher in morning
than evening).
Large elastic arteries are responsible for the Windkessel effect.
The Windkessel effect: Large elastic arteries distend (stretch) when BP increases and recoil
when BP is low. This effect helps to buffer the fall in BP. As elasticity allows aorta to bulge
(stores energy) and rebound propels blood flow onwards.
Pulse pressure gives an indication of Cardiac output.
MAP = 1/3 PULSE PRESSURE + DIASTOLIC PRESSURE
We use a 1/3 of the pulse pressure as 2/3 of the cardiac cycle is spent in diastole.
Cardiac Output affects mainly systolic pressure.
Total Peripheral Resistance affects mainly diastolic pressure.
INTRINSIC CARDIOVASCULAR REFLEXES
Minimise fluctuations in MAP and maintain adequate perfusion.
Centrally regulated.
Reflexes help you to stop fainting when standing.
BARORECEPTOR REFLEX
Primary reflex regulating MAP.
Have carotid baroreceptors in carotid sinus and aortic baroreceptors in aortic sinus.
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