Regulation of Vascular Function Flashcards
What happens when you vasocontrsitc pre-capillary vessels?
- will increase pre-capillary resistance, and get a decrease pressure so will have a decrease flow of blood through capillary
- this will mean that we get a decrease in hydrostatic pressure, and will lead to an increase in absorption of fluid from tissues
What happens when you vasodilate pre-capillary vessels?
- will decrease pre-capillary resistance and increase pressure and blood flow across capillary
- this will cause an increase of hydrostatic pressure and lead to extrusion of fluid into tissues
Veins and constriction
- If we constrict veins, then get reduced capacity for them to store blood so an increase in driving pressure back to heart
- and opposite in dilation
auto regulation
tendency of an organ to maintain constant blood flow despite changes in perfusion pressure
- cerebral circualtion tightly regulated
- Myogenic control
- metabolic control
- endotehtlail control
- flow idnuced vasodilation
Myogenic control
increase in transmural pressure results in vascular contrraction and vice cersea
metabolic control
- if an organ is workign harder, demands increase need more flow
- this causes vasodilation to try and increase flow
- get metbolights formed hwen there is increased metabolism
Sympathetic activation
- Adreanline, noradrenaline bind to B2 or a2
- cause an increase in cyclic AMP, protein kinase A - and phosphorylates proteins - leads to increase calcium, and vasoconstrciton
Nerves
Pre synaptic
Get an AP, calcium enters cells
-get vesicles fuse w memrbane
-noradrenaline and adreanline released and cotransmitters
a2 receptors - noradreanline binds and inhibits release of further noradrenaline by closing calcium channels
inhibition - acetylcholine, adenosine, dopamine
exciation - angiotnsine 2, adrenaline
Vascular smooth muscle/post synaptic
-noradreanline binds to adrenoreceptors on VSM
-a1 - phosphorylates proteins and causes an increase in intracellualr calcium - vasoconstriction
-a2 receptors - get adenylate cyclase, get decrease in calcium concentrations, and get increase potassium out of cells - hyperpolarises = vasodilation
b2 - same affects as a2
Why do receptors vary in differnet organs?
- receptors vary in different organs, so that we can control the blood flow to certain areas
- e.g reduce blood to gut on SNS and get more going to muscles
- a1 and a2 receptors - can change amount on different cells in differnt organs to get diferent responses
PNS activation
Cholinergic nerves - ach binds to muscarinic receptors
-causes relaese of NO and vasodilation
What happens when given an injection of noradrenaline vs adrenaline
Noradrenaline - causes vasoconstriction on most areas apart from coronary and cerebral circulation (decrease skeletal muscle, skin, kidney, splanchnic)
Adrenaline - similar affects but in resistance vessels and in skeletal muscle ( increased skeletal muscle flow, splanchnic flow) decrease skin flow, kidney flow
affinity for receptors
- alpha - adrenaline, noradrenaline, isoprenaline
- beta 2 - isoprenaline, adrenaline, noradrenaline
Skeletal muscle circulation
Rest - vasoconstriction to blood vessels to stop blood flow there - effected by SNS
Exercise - vasodilation to decrease resistance and increase blood flow
however this activity is ineffective at high exercise rates and is more controlled by vasodilator metabolights
(similar to cardiac muscle)
Skin circulation
affinity for receptors decreases with temp
sympathetic cholenergic activation of sweat glands activates kinase cascade which
-tries to allow heat loss
Cerebral circulation
- tighlty autoregulated betwewen 60-180 mmHg
- local control mecahnismss - pH, pCO2, pO2
- decrease paCO2 - will lead to increas eblood flow and vice versa
- when pao2 drops below 50, then get blood flow increasing
