peripheral circulation exchange and control Flashcards
state how non-polar and polar substances diffuse:
non-polar substances e.g. O2 - diffuse across the phospholipid membrane
polar substances - diffuse through clefts/pores.
state the function of carrier-mediated transported:
they transport glucose to the brain because of the blood-brain barrier.
define bulk flow:
determined by starling forces
refers to the mass movement of fluid as the result of hydrostatic or osmotic pressure gradients
explain what the starling forces:
→ Capillary hydrostatic pressure vs ISF hydrostatic pressure
→ Plasma osmotic pressure vs ISF osmotic pressure
define hydrostatic and osmotic pressure:
Hydrostatic pressure - the pressure that favours the movement of fluid out of the capillaries.
→ depends upon the blood pressure.
Which in return generates opposing pressure…
Osmotic (Oncotic pressure) - the pressure that favours the movement of fluid into the capillaries.
→ depends upon the protein (albumin) in blood
how is colloid osmotic and oncotic pressure created?
by the presence of proteins e.g. albumin in plasma.
when is the net filtration pressure positive and negative?
positive → fluid is flowing out of the capillary (Filtration).
negative → fluid is flowing into the capillary (Absorption)
how do you calculate the net filtration pressure?
Net filtration pressure =
OUT Hydrostatic pressure - IN Oncotic/Osmotic pressure
describe the neural central control of blood flow:
it involves the sympathetic innervation
releasing noradrenaline, to most areas of the body except genitalia and salivary glands, which have parasympathetic innervation.
why does cerebral circulation show excellent pressure autoregulation?
it must be stable at all time
describe the response of hypoxia in pulmonary circulation:
the response is vasoconstriction, which is the opposite of most tissues.
– Ensures that blood is directed to the well-ventilated parts of the lung = V/Q matching!
describe how reactive hyperaemia is triggered:
by an occlusion of blood supply.
e.g. when putting a BP cuff (i.e. sphygmomanometer), it leads to constriction of the arm. Upon removal, the area is red. why?
Because there was a prior increase in [metabolites] and therefore release of EDRF
And upon removal, there is a quick arteriolar dilation which shows as redness
describe what EDRF is:
Endothelium-derived relaxing factor (EDRF) is an endogenous vasodilator that endothelial cells produce
