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Systems Physiology > Peripheral Circulation > Flashcards

Peripheral Circulation Flashcards

1
Q

What is blood flow controlled by

A

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

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2
Q

What is arteriolar resistance directly proportional to

A

1/r^4

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3
Q

What are the intrinsic controls of vascular smooth muscle

A

Controls located in tissues

  • Local temperature
  • Transmural pressure
  • Local metabolites, antacids and endothelium derived factors
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4
Q

What are the extrinsic controls of vascular smooth muscle

A

Nerves and hormones from outside the tissue

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5
Q

How can local temperature affect arteriolar radius and vascular smooth muscle

A
  • 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
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6
Q

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

A 
External = compresses vessels and impairs blood flow
Internal = stretch of the vessel causes the vessel to contract - the myogenic response
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7
Q

How can stretch sensitive membrane areas affect vascular smooth muscle

A

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)

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8
Q

How can local metabolites affect vascular smooth muscle/arteriolar radius

A
  • Vasodilators released by tissue in proportion to tissue metabolism
  • removal rate proportional to blood flow
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9
Q

Name some possible local metabolites that can affect vascular smooth muscle

A
  • K+ ions
  • Adenosine
  • Hypoxia
  • Acidosis
  • Increased interstitial osmolarity
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10
Q

What are autacoids

A

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

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11
Q

What is the basic mechanism of autacoids in response to inflammation

A

Increases the permeability of the microcirculation

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12
Q

Give some examples of autacoids

A
  • Histamine
  • Bradykinin
  • Serotonin (5-HT)
  • Arachidonic Acid Derivatives
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13
Q

What are the signs and symptoms of inflammation

A 
Heat 
Redness
Swelling
Pain
Loss of Function
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14
Q

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

A

Nitric Oxide

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

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15
Q

How does Nitric oxide act as an EDRF

A
  • Diffuses to underlying smooth muscle

- Activates soluble granulate cyclase to increased cGMP and cause relaxation

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16
Q

What stimulates EDRF production and when is it stimulated too much

A
  • Basal production stimulated by autacoids and shear stress

- Production stimulated too much in infection

17
Q

What are endothelins

A

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

18
Q

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

A
  • found in smooth muscle tissue of blood vessels also the nervous system
  • binding causes vasoconstriction, retention of sodium and leads to increased blood pressure
19
Q

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

A
  • 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
20
Q

What does poiseuille’s law describe

A

the factors affecting blood flow

21
Q

What is flow rate inversely proportional to

A

The length of the tube and the viscosity of the blood

22
Q

What is flow rate directly proportional to

A

Resistance/Pressure difference

Flow = DeltaP/R

23
Q

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

A

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

24
Q

What does the sympathoadrenal system play a role in maintaining

A

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

25
Q

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

A

Increases it all

26
Q

How does the sympathoadrenal system increase blood flow to the muscles

A

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

27
Q

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

A

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

28
Q

Name some paracrine regulators produced by the endothelium that promote relaxation

A

Nitric Oxide
Bradykinin
Prostacyclin

29
Q

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

A

Nitric Oxide

30
Q

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

A

Parasympathetic activity

31
Q

What paracrine regulator do drugs like nitroglycerin or viagra act through

A

Nitric Oxide

32
Q

What is Endothelin 1

A

(ETa) This is a vasoconstrictor produced by the endothelium

33
Q

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

A

To maintain a fairly constant blood flow despite BP variation

34
Q

How do myogenic control mechanisms of blood flow work

A

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

35
Q

What effect can arterial pressure have on cerebral vessels

A

Decreased arterial pressure = dilation of cerebral vessels

36
Q

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

A

To match the blood flow to the local tissue needs

37
Q

What is hyperaemia

A

An excess of blood in the vessels supplying an organ

38
Q

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

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

Systems Physiology (28 decks)

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