Peripheral Circulation

Question 1

What is blood flow controlled by

Answer 1

The contraction of the smooth muscle of arterioles as arteriolar radius controls resistance

Question 2

What is arteriolar resistance directly proportional to

Answer 2

1/r^4

Question 3

What are the intrinsic controls of vascular smooth muscle

Answer 3

Controls located in tissues

• Local temperature
• Transmural pressure
• Local metabolites, antacids and endothelium derived factors

Question 4

What are the extrinsic controls of vascular smooth muscle

Answer 4

Nerves and hormones from outside the tissue

Question 5

How can local temperature affect arteriolar radius and vascular smooth muscle

Answer 5

• High temp = vasodilation of cutaneous arterioles and veins
• Skin cooling = vasoconstriction by slowing Na+/K+ ATPase that causes depolarisation
• Skin cooling below 12C = vasodilation by paralysis of smooth muscle

Question 6

How does the external and internal pressure of transmural pressure affect vascular smooth muscle

Answer 6

External = compresses vessels and impairs blood flow
Internal = stretch of the vessel causes the vessel to contract - the myogenic response

Question 7

How can stretch sensitive membrane areas affect vascular smooth muscle

Answer 7

Stretch in these areas opens a stretch activated ion channel and cells become depolarised and results in a Ca2+ signal and triggers muscle contraction
(local vasodilators from endothelium also help do things)

Question 8

How can local metabolites affect vascular smooth muscle/arteriolar radius

Answer 8

• Vasodilators released by tissue in proportion to tissue metabolism
• removal rate proportional to blood flow

Question 9

Name some possible local metabolites that can affect vascular smooth muscle

Answer 9

• K+ ions
• Adenosine
• Hypoxia
• Acidosis
• Increased interstitial osmolarity

Question 10

What are autacoids

Answer 10

Local hormones and molecules that are released by cells and tissues in response to inflammation

Question 11

What is the basic mechanism of autacoids in response to inflammation

Answer 11

Increases the permeability of the microcirculation

Question 12

Give some examples of autacoids

Answer 12

• Histamine
• Bradykinin
• Serotonin (5-HT)
• Arachidonic Acid Derivatives

Question 13

What are the signs and symptoms of inflammation

Answer 13

Heat 
Redness
Swelling
Pain
Loss of Function

Question 14

Give an example of an endothelium derived relaxing factor (EDRF)

Answer 14

Nitric Oxide

Thats all the powerpoint said so if you said something else then fook you

Question 15

How does Nitric oxide act as an EDRF

Answer 15

• Diffuses to underlying smooth muscle

- Activates soluble granulate cyclase to increased cGMP and cause relaxation

Question 16

What stimulates EDRF production and when is it stimulated too much

Answer 16

• Basal production stimulated by autacoids and shear stress

- Production stimulated too much in infection

Question 17

What are endothelins

Answer 17

Endothelins are proteins that affect vasoconstriction of blood vessels and blood pressure

Question 18

Where are ETa receptors found and what happens when endothelins bind to them

Answer 18

• found in smooth muscle tissue of blood vessels also the nervous system
• binding causes vasoconstriction, retention of sodium and leads to increased blood pressure

Question 19

Where are ETb receptors found and what happens when endothelins bind to them

Answer 19

• found on endothelial cells that line the interior of blood vessels also the nervous system
• binding causes release of nitric oxide, natriuresis and diuresis that leads to a lower blood pressure

Question 20

What does poiseuille’s law describe

Answer 20

the factors affecting blood flow

Question 21

What is flow rate inversely proportional to

Answer 21

The length of the tube and the viscosity of the blood

Question 22

What is flow rate directly proportional to

Answer 22

Resistance/Pressure difference

Flow = DeltaP/R

Question 23

In extrinsic regulation of blood flow what happens when the SNS activates the adrenal medulla

Answer 23

Norepinephrine and epinephrine are rebased directly into the blood where they act as the mechanism for the fight or flight response

Question 24

What does the sympathoadrenal system play a role in maintaining

Answer 24

Glucose levels, sodium levels, blood pressure and other metabolic pathways

Question 25

How does sympathoadrenal activation affect Cardiac Output and resistance in the periphery and viscera

Answer 25

Increases it all

Question 26

How does the sympathoadrenal system increase blood flow to the muscles

Answer 26

Their arterioles dilate in response to adrenaline via Beta2 adrenoceptor stimulation. So blood is shunted away from visceral and skin towards the muscles

Question 27

What effects do AT2 and ADH at high levels have on peripheral circulation

Answer 27

General vasoconstriction of vascular smooth muscle, which increases resistance and BP

Question 28

Name some paracrine regulators produced by the endothelium that promote relaxation

Answer 28

Nitric Oxide Bradykinin Prostacyclin

Question 29

Which paracrine regulator is involved in setting the resting 'tone' of vessels

Answer 29

Nitric Oxide

Question 30

What extrinsic factor increases NO (endothelial derived relaxing factors) levels

Answer 30

Parasympathetic activity

Question 31

What paracrine regulator do drugs like nitroglycerin or viagra act through

Answer 31

Nitric Oxide

Question 32

What is Endothelin 1

Answer 32

(ETa) This is a vasoconstrictor produced by the endothelium

Question 33

What is the role of intrinsic and extrinsic regulation of blood flow

Answer 33

To maintain a fairly constant blood flow despite BP variation

Question 34

How do myogenic control mechanisms of blood flow work

Answer 34

Occurs because vascular smooth muscle contracts when stretched and relaxes when not stretched

Question 35

What effect can arterial pressure have on cerebral vessels

Answer 35

Decreased arterial pressure = dilation of cerebral vessels

Question 36

What is the role of the metabolic control mechanisms of blood flow

Answer 36

To match the blood flow to the local tissue needs

Question 37

What is hyperaemia

Answer 37

An excess of blood in the vessels supplying an organ

Question 38

What factors resulting from high metabolism can cause vasodilation and increased blood flow

Answer 38

``` Low O2 Low pH High CO2 High Adenosine High K+ ```