CVS 6 - Blood Vessel Order, Function and Specialisation of cells in the CVS

Question 1

What is the vascular endothelium?

Answer 1

Single layer of cells which acts as the blood-vessel interface.

Question 2

What are the 5 functions of vascular endothelium?

Answer 2

1. Vascular tone management - secreting/metabolising vasoactive substances
2. Thrombostasis - secreting anti-coagulant substances
3. Absorption + Secretion
4. Barrier - prevents atheroma development and impedes pathogens
5. Growth - mediates cell proliferation

Question 3

What are the 2 vasodilators?

Answer 3

1. Nitric Oxide

2. PGI2 (prostacyclin)

Question 4

What are 3 vasoconstrictors?

Answer 4

1. TXA2 (thromboxane)
2. ET-1 (endothelin 1)
3. Angiotensin 2

Question 5

How is vascular tone controlled?

Answer 5

By the balance of forces causing vasoconstriction and vasodilation

Question 6

What can shear stress do?

Answer 6

It is a stimulator, which upregulates endothelial NO.

Question 7

Give another way in which Arachidonic acid can be made?

Answer 7

Via DAG lipase.

Question 8

NO has a short half life

Answer 8

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Question 9

Where is angiotensinogen produced?

Answer 9

In the liver

Question 10

When is renin secreted?

Answer 10

Renin is secreted by the kidneys if BP is low

Question 11

What does renin do?

Answer 11

Converts angiotensinogen into Angiotensin 1

Question 12

What happens to Angiotensin 1?

Answer 12

It is converted into angiotensin 2 by ACE enzyme.

ACE is found in pulmonary circulation and renal circulation.

Question 13

What 5 things does Angiotensin 2 do?

Answer 13

1. Stimulates ADH secretion
2. Increases aldosterone production
3. Increases Na reabsorption.

(THESE 3 INCREASE WATER RETENTION)

4. Increases sympathetic activity
5. Increases vasoconstriction

(THESE 2 INCREASE VASCULAR RESISTANCE)

Increased water retention and increased vascular resistance leads to increased BP

Question 14

What do ACE inhibitors do?

Whats another thing we can do?

Answer 14

1. ACE inhibited, so Ang 1 to Ang 2 conversion decreases.
2. Bradykinin breakdown also reduced.

Block angiotensin 2 receptors on VSMC

Question 15

How can Ca channel blockers be used?

Answer 15

Block Ca channels (much greater extracellular Ca than intracellular).

Affinity of Ca channel blocker is related to membrane potential of target cells; VSMC have higher membrane potential than cardiomyocytes.

Question 16

How does aspirin work?

Answer 16

It causes irreversible inhibition of the COX enzymes.

other NSAIDs cause reversible inhibition of COX

Question 17

What effect does aspirin have on COX 1 enzymes?

Answer 17

Inactivation of enzyme (acetylated)

Question 18

What effect does aspirin have on COX 2 enzymes/

Answer 18

Switches COX 2 function to generating protective lipids

Question 19

Aspirin inhibits both prostacyclin and thromboxane. We want to inhibit thromboxane not prostacyclin. How?

Answer 19

Thromboxane is mainly produced in platelets, which have no nucleus. Therefore, they can’t produce more mRNA for building more COX enzymes.

This is why there is only a small decrease in prostacyclin but a large decrease in thromboxane.

Question 20

COX 2 specific inhibitors cause reversible inhibition of COX 2 isoforms only.

Answer 20

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