Autonomic control of vasculature

Question 1

Vascular smooth muscle

Answer 1

Is continuously active.
Is influenced by substances released from endothelium and nerves in the advantitia.
Nerves are activated from the CNS.
Endothelium is activated locally by blod flow and hormones.

Question 2

Sympathetic action on vasculature

Answer 2

Vasoconstriction

NA, Adr, Atp and NPY

Question 3

Parasympathetic action on vasculature

Answer 3

Vasodiltion

NO, nitrergic plus cotransmission.

Question 4

Large arteries

Answer 4

Small innervation and respond to some vasoconstrictors by stiffening (compliance)

Question 5

Small arteries

Answer 5

Are the most important vessels where nerves control BP and flow (resistance). Alpha and beta2 receptors present.

Question 6

Veins

Answer 6

Controlled by sympathetic nerves (capacitance).

Alpha receptors.

Question 7

Vascular beds

Answer 7

Central influence comes via sympathetic nervous sytem. This is nearly always on, so can produce vasoconstriction or vasodilation by increasing/decreasing transmitter traffic. Local factors can interact with this either at VSM (synergism or override) or by altering transmitter output.

Question 8

Adrenals

Answer 8

Release catecholamines into blood

Question 9

Adrenaline

Answer 9

Can raise and lower BP by acting at different receptors.
Causes vasoconsttiction by acting on alpha receptor (fast reaction).
Causes vasodilation by acting on B2 receptor (slower overriding reaction, Adr more potent here).

Question 10

Angiotensin II

Answer 10

Causes vasoconstrictionvia AT1 receptors.

Comes via blood or is made frkm angiotensin I by ACE in the Endothelium.

Question 11

Synergism

Answer 11

Low conc vasoconstricters (NA,Adr,AngII) produce synergism, where combined effect is greater than the sum of the parts.
This explains why blocking just one of several neurohormones has a profound effect on lowering BP.