CVS 6 - Blood Vessel Order, Function and Specialisation of cells in the CVS Flashcards
What is the vascular endothelium?
Single layer of cells which acts as the blood-vessel interface.
What are the 5 functions of vascular endothelium?
- Vascular tone management - secreting/metabolising vasoactive substances
- Thrombostasis - secreting anti-coagulant substances
- Absorption + Secretion
- Barrier - prevents atheroma development and impedes pathogens
- Growth - mediates cell proliferation
What are the 2 vasodilators?
- Nitric Oxide
2. PGI2 (prostacyclin)
What are 3 vasoconstrictors?
- TXA2 (thromboxane)
- ET-1 (endothelin 1)
- Angiotensin 2
How is vascular tone controlled?
By the balance of forces causing vasoconstriction and vasodilation
What can shear stress do?
It is a stimulator, which upregulates endothelial NO.
Give another way in which Arachidonic acid can be made?
Via DAG lipase.
NO has a short half life
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Where is angiotensinogen produced?
In the liver
When is renin secreted?
Renin is secreted by the kidneys if BP is low
What does renin do?
Converts angiotensinogen into Angiotensin 1
What happens to Angiotensin 1?
It is converted into angiotensin 2 by ACE enzyme.
ACE is found in pulmonary circulation and renal circulation.
What 5 things does Angiotensin 2 do?
- Stimulates ADH secretion
- Increases aldosterone production
- Increases Na reabsorption.
(THESE 3 INCREASE WATER RETENTION)
- Increases sympathetic activity
- Increases vasoconstriction
(THESE 2 INCREASE VASCULAR RESISTANCE)
Increased water retention and increased vascular resistance leads to increased BP
What do ACE inhibitors do?
Whats another thing we can do?
- ACE inhibited, so Ang 1 to Ang 2 conversion decreases.
- Bradykinin breakdown also reduced.
Block angiotensin 2 receptors on VSMC
How can Ca channel blockers be used?
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.
How does aspirin work?
It causes irreversible inhibition of the COX enzymes.
other NSAIDs cause reversible inhibition of COX
What effect does aspirin have on COX 1 enzymes?
Inactivation of enzyme (acetylated)
What effect does aspirin have on COX 2 enzymes/
Switches COX 2 function to generating protective lipids
Aspirin inhibits both prostacyclin and thromboxane. We want to inhibit thromboxane not prostacyclin. How?
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.
COX 2 specific inhibitors cause reversible inhibition of COX 2 isoforms only.
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