4.1 Local control of blood flow

Question 1

what is the process of contraction in vascular smooth muscle?

Answer 1

Calcium calmodulin complex binds to MLC-Kinase to allow cross bridge cycling

Question 2

What receptors are found on vascular smooth muscle?

Answer 2

Alpha 1 and 2, Beta 2, P2x (mainly Alpha 1 and p2x)

Question 3

What blocks the sympathetic activation of vascular smooth muscle cells?

Answer 3

Nifedipine

Question 4

What binds to alpha 1 and P2x channels on vascular smooth muscle and what kind of excitatory junction potentials are formed?

Answer 4

P2X: ATP (ast EJP)

Alpha 1: NA (slow EJP)

Question 5

What causes the AP in vascular smooth muscle cells?

Answer 5

CALCIUM

Question 6

what happens in voltage dependent contraction in vascular smooth muscle?

Answer 6

NA binds to alpha 1 which activates DAG which causes the opening of voltage sensitive calcium channels, this leads to increased cytosolic calcium and MLCK activation leading to contraction

Question 7

What happens in voltage independent contraction of vascular smooth muscle?

Answer 7

NA binds to alpha 1 which opens TRPC channels and activation of protein kinase C. This leads to Calcium sensitization and MLCK activation and contraction

Question 8

How does vascular smooth muscle relax?

Answer 8

Adrenaline binds to B2 receptors which sets of Gs. This leads to activation of protein kinase A which stimulates calcium extrusion, K efflux and inhibition of MLCK

Question 9

What are the three outcomes of protein kinase A?

Answer 9

Ca pump stimulation and calcium extrusion
K efflux - hyperpolarization
Inhibition of MLCK

Question 10

What are the tree tiers of vascular control?

Answer 10

Bottom: autoregulation by myogenic response
Middle: autoregulation mediated by locally produced vasoactive agents
Top: extrinsic regulation by nerves and circulating hormones

Question 11

What controls the myogenic response of vascular control?

Answer 11

stretch activated channels which increases cytosolic Ca causing constriction and decrease in flow

Question 12

What are the three methods of relaxation in endothelial - VSMC interaction (middle tier)?

Answer 12

1. NO diffuses to VSMC - increases cGMP - relaxation (directly an via K activation)
2. PGI2 binds to receptor on VSMC - increase cAMP - relaxation
3. Hyperpolarization via calcium activated K channels - EDHF as mechanism and spread via myo-endothelial gap junction - closes VDCC - relaxation

Question 13

What is the catalyst for relaxation in the middle tier?

Answer 13

Sheer stress causing NO release