25 Vascular tone regulation

Question 1

________ is a Ca2+-binding protein to form a complex
which regulates smooth muscle contraction and
many other cellular functions.

Answer 1

Calmodulin

Question 2

Ca2+/calmodulin will cause phosphorylation of ___________ by ___________. It results in smooth muscle __________.

Answer 2

Myosin light chain
Myosin light chain kinase

contraction

Question 3

_________ will convert MLC-P + actin into MCL, causing smooth muscle relaxation.

Answer 3

Myosin light chain phosphatase

Question 4

Noradrenaline, AngII, endothelin and vasopressin are coupled to _________ protein. What are the following reactions?

______ on SR is also activated

Answer 4

Gq
PLC causes PIP2 > IP3
IP3 + DAG > release intracellular Ca2+ from sarcoplasmic reticulum

Ryanodine receptors

Question 5

To inhibit Ca2+ influx via voltage-gated Ca2+ channel, we can use L-type channel blockers.
List 3 examples.

Answer 5

Dihydropyridines (nifedipine)
Phenylalkylamines (verapamil)
Benzothiazepines (diltiazem)

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Question 6

Ca2+ channel blockers are used clinically in ?

Answer 6

Controlling hypertension by reducing vascular resistance

Question 7

What are the 4 main [Ca2+i] lowering mechanisms?

Answer 7

1. SERCA Ca2+ pump, uptake Ca2+ ions to SR
2. Plasma Ca2+ pump to remove part of the increased intracellular Ca2+ ions
3. Closure of voltage gated Ca2+ channels by membrane hyperpolarization from opening of K+ channels
4. Na+/Ca2+ exchanger (3 Na+ in, 1 Ca2+ out)

Question 8

Defective ______ channels have been implicated in pulmonary hypertension.

Answer 8

K+

Reduced in K+ channel activity tends to cause depolarization and subsequent activation of Ca2+ channels that increases intracellular [Ca2+]

Question 9

What do beta 2 agonist, VIP and adenosine do in vascular tone?

Answer 9

bind to endothelial cells Gs protein, increase cAMP by stimulating AC, thus PKA increases. Hyperpolarization occurs, reduce intracellular Ca2+. Vasodilation.

Question 10

What do noradrenaline, endothelin 1 and angiotensin II do in vascular tone?

Answer 10

they bind to a1 receptors can activate Gq protein. Increase in PLC, converting PIP2 to IP3, + DAG > increase SR Ca2+ release> vasoconstriction

Question 11

What are the 3 vasoconstrictors that are hormones in nature?

Answer 11

Angiontensin II, vasopressin, endothelin

Question 12

What are the 3 vasodilators that are hormone in nature?

Answer 12

1. CGRP (Calcitonin gene-related peptide)
2. Atrial natriuretic peptide (ANP)
3. VIP (vasoactive intestinal polypeptide)