Regulation of arteriolar resistance

Question 1

What is Darcy`s Law?

Answer 1

Flow is equal to pressure diff devided by resistance

Question 2

What is Poiseuille`s Law?

Answer 2

Resistance is equal to viscosity by length by 8 divided by radius to the power of 4 x pi

Question 3

What does increasing the haematocrit do?

Answer 3

Increases viscosity of blood

Question 4

Pressure is equal to what?

Answer 4

Flow x Resistance

Question 5

How can you apply pressure = flow x resistance to systemic circulation?

Answer 5

MAP- CVP= COx TPR

Question 6

Why can CVP be ignored?

Answer 6

Because its so small

Question 7

What is the average MAP?

Answer 7

90/95mmHg

Question 8

What is the average CVP?

Answer 8

0-5mmHg

Question 9

What happens when total peripheral resistance is reduced?

Answer 9

Mean arterial pressure is also reduced

Question 10

Can you affect one vascular bed and not mean arterial pressure

Answer 10

NO YE GIT

Question 11

How do you keep the blood flow to each vascular bed sufficient and keep mean arteial pressure in the right range?

Answer 11

Intrinisc mechanisms -selfish needs of each individual tissue
Extrinsic mechanisms-

Question 12

How does the sympathetic system affect extrinsic control?

Answer 12

• releases norepinephrine
• binds to alpha1- receptors
• Causes arteriolar constriction
• Reduces flow through tissue and increases TPR

Question 13

What effect does parasympathetic system have on extrinsic control?

Answer 13

NON

Question 14

How does hormonal control affect Extrinic control?

Answer 14

ADRENALINE
(released from adrenal medulla)
-Binds to alpha 1 receptors
-causes arteriolar consriction
-Therefore decrease flow through that tissue Increase TPR

IN SOME cases
-binds B2 receptors in skeletal and cardiac to cause arteriolar dilation

Question 15

What effect does Angiotensin 2 have?

Answer 15

Causes arteriolar constriction

Increases TPR

Question 16

When is angiotensin 2 produced?

Answer 16

in response to low blood volume

Long term porduced in kidney

Question 17

When is vasopressin released?

Answer 17

in response to low blood volume

Question 18

What is another name for vasopressin?

Answer 18

antidiuretic hormone

Long term porduced in kidney

Question 19

When are artial natriuretic peptide & brain natriuretic peptide released?

Answer 19

-Released in response to high blood volume

Question 20

What does artial natriuretic peptide & brain natriuretic peptide do?

Answer 20

-Causes artiolar dilation
Decreases TPR
(Long term produced in kidney)

Question 21

What does EDRF mean?

Answer 21

endothelium derived relaxing factor

Question 22

Why is EDRF released?

Answer 22

in response to metabolites from hard working tissue

Question 23

Name some of the metabolites released by hard working tissue

Answer 23

• CO2
• H+
• K+

Question 24

What does EDRF cause?

Answer 24

arteriolar dialitation

Question 25

Why does EDRF cause arteriolar dilation?

Answer 25

To wash out metabolites

Question 26

How does the body respond to a decrease in MAP and flow locally?

Answer 26

Releases EDRF

Question 27

What is reactive hyperaemia

Answer 27

- occulsion of blood (rubber band on arm) supply causes a subsequent increase in blood flow - (an extreme version of pressure autoreg)

Question 28

Describe the injury response?

Answer 28

C fibres pick up pain release substance P which causes mast cells to release histamine Increased permeability causes white cells to be allowed out

Question 29

What does histamine cause?

Answer 29

increase in blood flow | increase in permeability

Question 30

What happens when heart contracts ?

Answer 30

It cuts off its own blood supply

Question 31

How does coronary circulation cope with increased demand during exercise?

Answer 31

- excellent hyperaemia - Expresses many B2 receptors - These swamp any sympathetic arteriolar constriction

Question 32

What type autoregulation does the cerebral circ show?

Answer 32

Excellent pressure autoregulation

Question 33

What is the main function of renal circ?

Answer 33

Filtration which depends on pressure

Question 34

What do changes in MAP have a big affect on?

Answer 34

Blood volume

Question 35

What type of auto regulation does the renal circ show?

Answer 35

Excellent pressure regulation

Question 36

What is pressure regulation?

Answer 36

EDRF released in response to MAP decreased and decreased flow