11. Blood Flow and regulation- Overview of vascular system and the banjo.

Question 1

Where is blood stored in the vascular system?

Answer 1

Heart- 9%

Arteries- 11%

Arterioles and capillaries- 7%

Pulmonary circualtion- 12%

Veins and venules- 61%

Question 2

What is meant by a capaticence vessel

Answer 2

Vessel that allows for storage to avoid fludi overload e.g. in the lungs.

Question 3

What junctions exist between the endothelium

Answer 3

Tight junctions

Question 4

What are the functions of the endothelium

Answer 4

Barrier (prevent leakage)

Produce mediators to control constriction and dilaiton of blood vessels

Help with clotting system- VwF

Allow macrophage entry to damaged tissue

Question 5

What vasoactive substances are produced by vascular endothelium

Answer 5

VASODILATORS- Nitric oxide, prostacyclin, Endothelium derived relaxing factors

VASOCOSTRICTORS- endothelin I, Angiotensin II,

ACE- catalyses conversion of angiotensin I to angiotensin II

Question 6

What are the three types of nitric oxide?

Answer 6

endogenous nitric oxide- always expressed

neural nitric oxide- always expressed

inflammtory nitric oxide- expressed during inflammatory response

Question 7

What is meant by sheer-stress

Answer 7

Blood flows across endothelial cells causing pressure.

This triggers intracellular activation of calcium due to either small proteins sticking out from membranes

OR this may be due to the stretch on ion channels

Question 8

What is some homework/exam research

Answer 8

Talk about what triggers sheer stress

Question 9

Where is calcium concentration highest

Answer 9

Outside the cell

Question 10

What mediatiors can cause calcium to enter cells via receptors?

Answer 10

Acetylcholine
Thrombin
Bradykinin
Adrenaline?

Question 11

How does increased calcium within the cell lead to increased produciton of nitric oxide

Answer 11

Calcium binds to calmodulin which tiggersL-arginine to activate eNOS

Question 12

What is the half life of nitric oxide

Answer 12

Very short- 5-10s

However passes very readily through cell membranes

Question 13

How does nitric oxide impact smooth muscle cells?

Answer 13

Activates cyclic GMP leading to a decrease in calcium leading to a smooth muscle relaxation

Question 14

How is prostaglandin I2/ prostacyclin produced?

Answer 14

Formed from cycloendogenous enzymes that use arachidonic acid (due to calcium increase)
to produce prostacylin.

Question 15

How does prostaglandin act on smooth muscle?

Answer 15

Acts on receptors on the cell membrane binding to cyclic AMP decreasing calcium and releasing potassium

Potassium leaving means the cell is less polarised being less likely for the smooth muscle to be activated

Question 16

What is EET and how does it affect smooth muscle?

Answer 16

Endothelial derived hyprepolorising factors

Hyperpolorises cell again by allowing potassium to leave the cell

Potassium can also mimic EET and diffuse via gap juncitons. Potassium coming into the cell allows for a reduction in potassium.

Question 17

What can be said about NO and size of blood vessel, age effects and interactions between NO and prostacyclin

Answer 17

Blood vessel size- Smaller the blood vessel. EDHF becomes more important comapred to NO

Age effects- EDHF/NO ratio declines with age

Prostacyclin- When they are co-activated they produce a synergistic effect. (bigger increase than expected)