6 - Blood vessel order, function and specialisation of cells in the CNS

Question 1

What is the Tunica adventitia?
What is made up of?
What is its purpose?

Answer 1

• The external layer of the blood vessels
• contains fibrous tissue, elastin and collagen
• helps to keep the shape of the blood vessel

Question 2

What is the Tunica media?
What is its made up of?
What is its purpose?

Answer 2

• middle layer of the blood vessel

- predominantly smooth muscle cells that allow the vessel to contract and relax

Question 3

What is the Tinuca intima?

What is it made up of?

Answer 3

• the exchange surface

- predominantly vascular endothelium and includes the elastic basal lamina as well

Question 4

What is the vascular endothelium?

Answer 4

a single layer of cells that acts as the blood-vessel interface

Question 5

Give the 5 main vascular endothelium functions

Answer 5

• vascular tone management
• thrombostasis
• absorption and secretion
• barrier
• growth

Question 6

What other 2 stimulators are there that will upregulate the endothelial NO?

Answer 6

shear stress

acetylcholine

Question 7

What is arachidonic acid?

Answer 7

it is a precursor of lots of molecules

Question 8

How are prostoglandins produced?

Answer 8

from arachidonic acid catalysed by COX enzymes

Question 9

Where is COX1 produced?

Answer 9

In all cells

Question 10

What is COX2 associated with?

Answer 10

inflammation and, hence, disease

Question 11

What 2 vasoactive compounds can be produced from prostaglandins?
What are the enzymes involved in each?
What are the roles of the products?

Answer 11

- prostacyclin
by prostacyclin synthase
a vasodilator
- thromboxane A2
by thromboxane synthase
a powerful vasoconstrictor (which stimulates platelet aggregation)

Question 12

Summary:

What 2 things can be produced from arachidonic acid?

Answer 12

prostoglandins or leukotrienes

Question 13

Summary:

What 2 things are produced from prostaglandins?

Answer 13

prostocylin and thromboxane

Question 14

Summary:

In what 2 ways is arachidonic acid produced?

Answer 14

• from phospholipids by Phospholipase A2

- from DAG via DAG lipase

Question 15

Where does the production of arachidonic acid and the production or prostaglandins and leukotrienes take place?

Answer 15

inside the endothelial cells

Question 16

Inside the nucleus, an endothelin precursor is produced and then cleaved by what enzyme to produce endothelin-1?

Answer 16

Endothelin Converting Enzyme

Question 17

Where does endothelin-1 act on once it has been produced?

Answer 17

It is pushed out of the endothelial cells and binds to alpha and beta receptors on smooth muscle cells
NOTE: both receptors perform the same function in this context

Question 18

What kind of effect does endothelin-1 have?

Answer 18

generally, it causes contraction

• if it binds to receptors on SM cells it causes contraction
• if it binds to receptors on endothelial cells, it causes relaxation

Question 19

Where and when is rennin produced?

Answer 19

in the liver

in response to low BP (if renal perfusion decreases)

Question 20

What overall effect does angiotensin II have?

Answer 20

Increases BP

Question 21

Where is angiotensin II produced and where does it act on?

Answer 21

ACE is an enzyme on the endothelial cells

Angiotensin II binds to receptors on VSMCs

Question 22

Describe the mechanism of action of angiotensin II

Answer 22

binds to an angiotensin receptor on VSMCs which leads to an activation of PLC—–> causing the conversion of PIP2 into IP3, resulting in contraction.
It also breaks down bradykinin, which normally stimulates vasodilation/relaxation

Question 23

What effect does aspirin have on COX1 and COX 2?

Answer 23

COX1 - causes inactivation

COX2 - switches its function (to generating protective lipids)

Question 24

Give a summary of the mechanisms of drug action of:
NO production 
NO action
prostacyclin action
thromboxane action
endothelin 1 action
angiotensin II action

Answer 24

Gq protein linked receptor (PLC, PIP2, IP3, DAG)
o	Nitric Oxide production
o	Thromboxane action
o	Endothelin 1 action
o	Angiotensin II action

Guanylate Cyclase (GTP, cGMP, Protein Kinase G)
o	Nitric Oxide action

Adnylate Cyclase (ATP, cAMP, Protein Kinase A)
o	Prostacyclin action