Blood pressure regulation Flashcards
What is Blood Pressure ?
the force per unit of area on a vessel wall exerted by the contained blood
PULSE PRESSURE = SYSTOLIC PRESSURE - DIASTOLIC PRESSURE
MEAN ARTERIAL PRESSURE = DIASTOLIC PRESSURE + PULSE PRESSURE / 3
REGULATION OF BLOOD PRESSURE
PRESSURE GRADIENT = CARDIAC OUTPUT X PERIPHERAL RESISTANCE
Parameters affecting BP
Cardiac output = amount of blood pumped out by each ventricle in 1 min.
CO = HR X SV
PRELOAD = degree of stretch of heart muscle. Frank starling law is that the higher the preload the higher the stoke volume
Contractility = contractile strength achieved at a given muscle length. The more Ca2+ there is the cytoplasm of muscles the higher the contractility
Afterload = back pressure exerted by arterial blood
What is peripheral resistance ?
measure of the amount of friction blood encounters as it passes through the vessels
Blood viscosity = internal resistance to flow in blood (thickness)
The longer and thicker the vessel length and diameter the higher the resistance
SHORT TERM MECHANISMS OF BP REGULATION
Cardiac centres :
- cardioaccelerator centre
- cardioinhibitory centre
Vasomotor centre :
- vasomotor fibres = smooth muscle of vessels
- higher sympathetic activity leads to higher vasoconstriction which leads to higher BP
- lower sympathetic activity which leads to lower vasoconstriction which means more relaxation and lower BP
Neural controls
- BARORECEPTORS
- CHEMORECEPTORS
- HIGHER BRAIN CENTRES
BARORECEPTORS
- pressure sensitive mechanoreceptors that respond to changes in arterial pressure and stretch
- high BP = high stretch = activation of cardiovascular centre = low BP
CHEMORECEPTORS
- receptors that respond to changes in blood levels of CO2, H+, and O2
neural controls involves cerebral cortex, hypothalamus, medulla oblongata
Hormonal controls
Adrenal medulla hormones (epinephrine and norepinephrine)
- stress = sympathetic response = increased CO and vasoconstriction
