Control of blood flow

Question 1

What is active hyperaemia?

Answer 1

Increase in blood flow following increase in metabolic activity

Question 2

As rate of metabolism increases, vasodilation takes place and there is an increase in blood flow. True or false?

Answer 2

True

Question 3

Active hyperaemia is an example of intrinsic control. Why?

Answer 3

Because no hormones or nerves are involved in the response and the changes are a direct effect of the reduction in oxygen and increased carbon dioxide levels on the arterioles themselves

Question 4

Active hyperaemia is in response to metabolic demand. When the rate of metabolite production has increased - vasodilation. True or false?

Answer 4

True

Question 5

When does reactive hyperaemia take place?

Answer 5

When flow has been interrupted - restores flow

Question 6

In reactive hyperaemia, vasodilation takes place in response to a _______ rate of metabolite removal

Answer 6

decreased

Question 7

Active and reactive hyperaemia have the same mechanism. What is the difference?

Answer 7

The difference is in what they respond to
active - increased metabolite production
reactive - decreased rate of metabolite removal

Question 8

What is the difference in the response of adrenaline binding to a1 receptors and B2 receptors?

Answer 8

Adrenaline binding to a1 receptors causes vasoconstriction

Adrenaline binding to B2 receptors causes vasodilation

Question 9

How does angiotensin II control arteriolar resistance?

Answer 9

Formation of angiotensin II is a two step process.
Angiotensinogen is converted to angiotensin I by renin
Angiotensin I is converted to angiotensin II by ACE
One of the many effects of angiotensin II is to promote vasoconstriction, therefore increasing TPR and MAP

Question 10

Which organ secretes renin?

Answer 10

Kidney

Question 11

How does vasopressin/ADH control arteriolar resistance?

Answer 11

Promotes vasoconstriction

Question 12

What is vasopressin secreted by?

Answer 12

Posterior pituitary gland

Question 13

Adrenaline has the same affinity for all receptors. True or false?

Answer 13

False

Question 14

In low concentrations, adrenaline binds to B2 receptors. True or false?

Answer 14

True - because it has a higher affinity for them and so promotes vasodilation

Question 15

In high concentrations, adrenaline binds only to a1 receptors. True or false?

Answer 15

False - binds to a1 and B2 receptors, the effect it has on vascular resistance depends on which type of receptor predominates.
Because a1 receptors are on arteriole smooth muscle, high conc of adrenaline usually causes vasoconstriction
B2 receptors predominate in vascular smooth muscle of cardiac and skeletal muscle so high conc of adrenaline causes vasodilation here

Question 16

Where are arterial baroreceptors found?

Answer 16

aortic arch and the carotid sinuses of the carotid arteries, in the neck

Question 17

What do baroreceptors do when arterial pressure rises?

Answer 17

When arterial pressure rises, arterial walls stretch and stretch the sensory endings of the baroreceptors within them, inducing depolarisation
APs sent to CNS by baroreceptor axons

Question 18

What happens to baroreceptors in hypertension?

Answer 18

Hypertension develops slowly over time. The accompanying rise in arterial pressure causes baroreceptors to lose their sensitivity, such that they become reset to a new higher pressure which becomes “normal”.
In these conditions, baroreceptors continue to regulate arterial pressure but they keep it at higher level than normal.
Hypertension cannot be corrected by baroreceptors once this reset has taken place

Question 19

CO can increase by 500% or more. True or false?

Answer 19

True

Question 20

TPR is adjustable by 20% to 400%. True or false?

Answer 20

True