Manipulation of Vascular tone

Question 1

What are the 3 main cell surface receptors

Answer 1

• Ion channels
• G-proteins
• Enzyme linked

Question 2

Describe ion channels

Answer 2

ligand binds receptor, channel opens and ions move through

Question 3

Describe G-protein coupled receptors

Answer 3

Signalling molecule binds and brings proteins together, activates effector and causes change inside the cell

Question 4

Describe the enzyme-linked receptors

Answer 4

Signalling molecule binds and sets off a series of intracellular messengers

Question 5

How does hydrophobic signalling molecules act on the nucleus

Answer 5

Cross the lipid bilayer, where they attach to a receptor to forma receptor hormone complex. Receptor hormone complex then affects protein synthesis to make more of the hormone

Question 6

How do hydrophilic signalling work

Answer 6

Needs help to cross the lipid bilayer

Attaches a membrane receptor, which then signals an intracellular second messenger

Question 7

What are the main elements that make up vascular smooth muscle ultrastructure

Answer 7

• Endothelial cell
• Internal elastic lamina
• Vascular smooth muscle cell

Question 8

What do vascular smooth muscle cells form

Answer 8

A functional syncytium

Question 9

Which vessel of the circulatory system have lots of VSM cells

Answer 9

Arterioles

Question 10

What effect is a result of the elastic nature of arterioles

Answer 10

The windkessel effect, ensures constant flow

Question 11

What is key in influencing vascular smooth muscle tone

Answer 11

Intracellular calcium

Question 12

What endothelial derived factors influence vasomotor tone

Answer 12

• Prostanoids
• Peptides (angiotensin-II)
• Endothelial derived hyperpolarising factors
• Endothelin
• Nitric oxide

Question 13

What type of cell surface receptors do prostoglandind use

Answer 13

G-protein coupled receptors, requiring an intracellular

Question 14

What is angiotensin 11

Answer 14

potent vasoconstrictor

Question 15

Where is angiotensin I converted to angiotensin II

Answer 15

The surface of an endothelial cell

Question 16

What is the renin-angiotensin-aldosterone system

Answer 16

Body’s response to low BP. Renin, which is released primarily by the kidneys, stimulates the formation of angiotensin in blood and tissues, which in turn stimulates the release of aldosterone from the adrenal cortex. This causes the body to retain water and increase BP.

Question 17

What is nitric oxide and what is it released by

Answer 17

A potent vasodilator

Released by sheer stress

Question 18

How does nitric oxide work

Answer 18

• Diffuses into the vascular smooth muscle cell
• stimulates cGMP through soluble guanylate cyclase
• cGMP activates protein kinase G
• Protein kinase G stimulates the reuptake of cytosolic calcium and the open of calcium activated potassium channels
• Cytosolic Calcium levels fall
• MLCK activity decreases
• Decreased cross bridge
• Relax

Question 19

What do endothelins do

Answer 19

Potent mediators of vasoconstriction

Question 20

How is local blood flow determined

Answer 20

By the relative open/closed state of arterioles

Question 21

What is Poiseuille’s law

Answer 21

Flow = [Pressure Difference x (pi radius^4)] / (8Length*Viscosity)

I.e. a decrease by 1mm creates a 16th fold increase in resistance

Question 22

How do metabolities induce vasodilation

Answer 22

• Low O2 = build up of local metabolites
• low O2 will induce vasodilation
• Will go into reactive hyperaemia, to clear built up metabolites

Question 23

What occurs in chronic hypoxia

Answer 23

Induces vascular growth (angiogenisis)