Lecture 13

Question 1

Which organ has the highest blood flow per unit mass?

Answer 1

Kidney

Question 2

Which organ has a high extra capacity for blood flow?

Answer 2

The myocardium

Question 3

What is the main determinant of flow?

Answer 3

Radius

Question 4

What are some extrinsic control mechanisms?

Answer 4

Vasodilator nerves, sympathetic vasoconstriction, endocrine hormones.

Question 5

What are the intrinsic control mechanisms?

Answer 5

Metabolic and reactive hyperaemia, autoregulation and myogenic response.

Question 6

What are some locally active vasodilators in metabolic hyperaemia?

Answer 6

ATP/adenosine, K+, CO2/lactic acid, hypoxia.

Question 7

What is the mechanism of adenosine causes vasodilation?

Answer 7

Binds to A2a receptor which activates adenyl cyclase to activate PKA. This phosphorylates MLCK which decreases its Ca2+ sensitivity for relaxation. It also binds to the A1 receptor which is associated with a K+ channel for hyperpolarisation

Question 8

Which blood vessels are very sensitive to CO2?

Answer 8

Cerebral blood vessels.

Question 9

Which blood vessels are sensitive to hypoxia for vasodilation?

Answer 9

Cerebral, skeletal muscle and myocardium.

Question 10

Which blood vessels vasoconstrict due to hypoxia?

Answer 10

Pulmonary vasculature.

Question 11

Describe reactive hyperaemia

Answer 11

This is an increase in flow following an occlusion or in response to ischaemia. The excess flow is proportional to the duration of the occlusion. Tissues become hypoxic and CO2 builds up to cause the vasodilation.

Question 12

Is the myogenic response endothelial depended?

Answer 12

No

Question 13

What is a calcium blocker?

Answer 13

Galodinium

Question 14

What is a chloride channel blocker?

Answer 14

Amiloride

Question 15

What is an autocoid?

Answer 15

A factor that acts locally to where it is produced.

Question 16

Where is histamine released from?

Answer 16

Mast cells

Question 17

What does histamine on H1 receptors do?

Answer 17

Vasoconstriction and increased permeability.

Question 18

What does histamine on H2 receptors do?

Answer 18

Vasodilation of arterioles.

Question 19

Where is serotonin released from?

Answer 19

endothelium and platelets. it causes vasoconstriction

Question 20

What prostaglandin causes vasoconstriction?

Answer 20

PGF

Question 21

What prostaglandins cause vasodilation?

Answer 21

PGE and PGI

Question 22

What does calcium binding to calmodulin activate to cause contraction?

Answer 22

activates MLCK which phosphorylates MLC-20 which activates contraction.

Question 23

What mechanisms cause relaxation?

Answer 23

PKA phosphorylates MLC phosphatase which removes the phosphate from MLC. It also phosphorylates MLCK which inactivates it to stop it phosphorylating MLC-20.

Question 24

What do Rho-kinase and CPI-17 cause?

Answer 24

Contraction by inhibiting MLC-phosphotase