regional circulation lecture 21

Question 1

what is basal tone?

Answer 1

vessels are in always in a partial state of contraction

Question 2

what is Resting state?

Answer 2

most arterioles are constricted due to sympathetic nervous system activity

Question 3

What happens to arterioles if you change sympathetic nerve activity

Answer 3

if you increase sympathetic activity the arterioles will vasodilate
if you decrease sympathetic activity the arterioles will constrict more than basal level.

Question 4

What is the importance of endothelial cells?

Answer 4

endothelial cells are the slippery inner surface of blood vessel they transduce information about blood flow between the blood and smooth muscles

Question 5

what are the endothelial factors that affect vasodilation or vasoconstriction

Answer 5

Prostaglandins
Nitric Oxide
Endothelin

Question 6

explain the relationship between nitric oxide and endothelial cells?

Answer 6

NO is a gas that is released from endothelial cells
The release of NO is stimulated by the shear-stress( scraping along sides of endothelial that’s caused by increase in blood flow) the mechanical stress

Question 7

what is the mechanism of nitric oxide on smooth muscle

Answer 7

NO diffuses into vascular smooth muscles and activates guanylyl cyclase which increases the intracellular concentration of cGMP which lead to vasodilation –> relaxation of vascular smooth muscle.

Question 8

what is the mechanism of PGI2 on smooth muscles?

Answer 8

stimulates an increase in cAMP which leads to vasodilation –> relaxation
- Inhibits platelet aggregation

Question 9

What is the mechanism of endothelin on smooth muscles

Answer 9

endothelin is released in response to stretching of blood vessels and is mediated by ETA—> vasoconstriction

Question 10

what is the response to an increase in NO and prostaglandins

Answer 10

arterioles dilate which allows for more blood flow and nutrients to flow to the skeletal muscles

Question 11

How do tissues tell local blood vessels that they need more blood?

Answer 11

through metabolites. the more metabolism that occurs in skeletal muscle cells the more breakdown of products from metabolism are released into interstitium which surrounds arterioles

Question 12

What are the metabolic vasodilators

Answer 12

High tissue CO2
Low tissue O2
Low Ph(acidosis)
Pi (from ATP breakdown)
Prostaglandins (PGI2)
Adenosine (from ATP breakdown)

Question 13

what is active (functional hyperemia?

Answer 13

When a tissue increases its metabolism (by working) blood flow increases

Question 14

What is the process of Hyperemia

Answer 14

• you increase metabolic activity of a tissue
• you get low oxygen and high metabolites in interstitial fluid
• arterioles dilate, decrease in precapillary sphincters tone which allows capillary to be perfused
• increased blood flow to organ