Regulation of Arteriolar Resistance

Question 1

How is blood flow controlled and directed?

Answer 1

By varying the radius of resistance vessels

Question 2

What controls total peripheral resistance and regulates mean arterial pressure?

Answer 2

Varying the radius of resistance vessels

Question 3

Changes in the radius of which blood vessels has the biggest effect of the circulation?

Answer 3

Arterioles

Question 4

How is blood vessel radius controlled?

Answer 4

Smooth muscles surrounding the vessels

Question 5

What are the two levels of control over the smooth muscle surrounding the arterioles?

Answer 5

Intrinsic mechanisms

Extrinsic mechanisms

Question 6

How do sympathetic nerves effect extrinsic control of smooth muscles?

Answer 6

Release norepinephrine
binds to alpha-1-receptors
Causes arteriolar constriction
Decreased flow and increases total peripheral resistance

Question 7

How do parasympathetic nerves effect extrinsic control of smooth muscles?

Answer 7

They do not have an effect usually

Question 8

How is extrinsic control of smooth muscles done hormonally?

Answer 8

Epinephrine is released from the adrenal medulla and acts as it does in the sympathetic system
However, in some tissues such as skeletal and cardiac muscle, it also activates beta-2-receptors which cases arteriolar dilation, increased flow and deceases TPR

Question 9

What is produced in response to low blood volume?

Answer 9

Angiotensin II

Question 10

What effect does angiotensin II have on blood flow?

Answer 10

Arteriolar constriction and increases TPR

Question 11

What is released in response to low blood volume?

Answer 11

Vasopressin the antidiuretic hormone

Question 12

What effect does Vasopressin have on blood flow?

Answer 12

Arteriolar constriction which increases TPR

Question 13

What is released in response to high blood volume?

Answer 13

Atrial natriuretic peptide

Brain natriuretic peptide

Question 14

What effect do Atrial natriuretic peptide and Brain natriuretic peptide have on blood flow?

Answer 14

Arteriolar dilation which decreases TPR

Question 15

What are the 4 methods of Intrinsic control of smooth muscles?

Answer 15

1. Active hyperaemia
2. Pressure autoregulation
3. Reactive hyperaemia
4. The injury response

Question 16

How does active hyperaemia work?

Answer 16

Increased metabolite activity increases metabolite concentration which releases EDRF. This causes arteriolar dilation to increase flow and wash out metabolites

Question 17

How does pressure auto regulation work?

Answer 17

Decrease MAP causes decreased flow so metabolites accumulate. This triggers the release of EDRF which causes arteriolar dilation and restores flow to normal

Question 18

How does reactive hyperaemia work?

Answer 18

Occlusion of blood supply causes a subsequent increase in blood flow