Regulating Blood Flow Flashcards
What is blood flow affected by
MAP Blood pressure (CO x TPR)
Where does the largest drop in pressure occur
Arterioles
What is arterioles role in terms of blood flow
Match blood flow (determined by pressure) with metabolic need of cells
What is the partial contraction of smooth muscle in vessels called
Tissue vessel tone
What is it called when tissue vessel tone reduces diameter
Vasoconstriction
When would vasoconstriction of the vessel tone occur
If some cells have higher metabolic need eg in exercise
What is vasodilation
When tissue vessel tones increase in radius and decrease TPR therefore BP decrease (BF increases)
What are the other way of saying arterioles
Sphincter
What are the 3 mechanisms which control the vessel tone and therefore affect BF
Local control
Hormone control
Neural control
What is auto regulation (local control) of vessel tone
Works on the fact if you increase pressure this will increase blood flow (P/ r)
What happens when there is increased pressure which increases BF
(In auto regulation)
Pressure will stretch muscles and this promotes Ca2 influx
This causes muscle contraction which therefore regulates blood flow by increasing resistance = lowered blood flow (P/R)
Metabolic control is also local, which metabolites cause vasodilation (increasing BF by decreasing resistance)
Co2, H+, K+ , temp, adenosine
Which metabolite causes vasoconstriction to increase resistance and decrease BF
Oxygen
Cells don’t need supply of blood flow as much
What are the 4 hormonal vasodilators which increase BF by reducing resistance
Histamine
NO
Kinins
Adrenaline
Which receptor does adrenaline need to bind to to be a vasodilator
B2
What does NO bind to which then produces cGMP for vasodilation
Guanylyl cyclase
What are the 3 vasoconstrictor hormones
Adrenaline (bound to A1)
ADH
Angiotensin II
What are the 3 neural controls of vessel tone / BF
Sympathetic vasoconstrictor fibres
Sympathetic vasodilation fibres
Parasympathetic vasodilation fibres
How do sympathetic vasoconstrictors work
They release adr/nadr
When bound to A1 this causes vasoconstriction
(Unlike in heart when they bind to B1)
What happens when there’s a lower frequency of sympathetic vasoconstrictor signals
Vasodilation due to less nadr binding at A1
What do sympathetic vasodilators release and the effect of it
Ach
This causes increased Ca2+ (via ip3)
This causes NO synthesis and therefore vasodilation
Do parasympathetic vasodilators work the same as sympathetic vasodilators
Yes
CO affects pressure which if increased will also increase BF, what happens to CO when exercising
Increased CO from heart which causes vasodilation of the vessels to skeletal muscle to increase BF for supplying o2
Why doesn’t BP increase during exercise despite CO increasing
Because TPR will decrease as vasodilation in vessels occurs to allow BF
