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Cvr > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

What is the overall aim of the cardiovascular system?

A

Adequate blood flow through the capillaries

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2
Q

What is the definition of the blood flow rate?

A

The volume of blood passing through a vessel per unit of time

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3
Q

What is the equation which describe the change in pressure in a fluid circuit?

A

Change in pressure (between A and B) = Flow rate (Q) x Resistance (R)

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4
Q

What is the pressure gradient?

A

The difference in pressure between Point A and Point B (Pressure when blood enters the 1st order arteriole - Pressure when blood enters capillaries)

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5
Q

What affect will increases in flow rate have on the pressure gradient?

A

It will increase the pressure gradient

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6
Q

Flow rate is proportional to…

A

Pressure gradient

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7
Q

Flow rate is inversely proportional to…

A

Resistance

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8
Q

What is the definition of resistance?

A

Hindrance to blood flow due to friction between moving fluid and stationary vascular walls

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9
Q

What is the equation for the resistance experienced in a vessel?

A

R = 8Ln / Pi r^4

Where L = vessel length
n = blood viscosity
r = radius

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10
Q

What part of the resistance equation is the most variable and can change from minute to minute?

A

The radius of the vessel

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11
Q

Why is having a pressure difference in the organs essential?

A

Otherwise blood would not reach tissue capillary beds

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12
Q

During Vasoconstriction, what happens to the radius, resistance and flow across the vessel?

A

Radius decreases
Resistance Increases
Flow decreases

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13
Q

During vasodilation, what happens to the radius, resistance and flow across the vessel?

A

Radius Increases
Resistance Decreases
Flow Increases

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14
Q

What is meant by vascular tone?

A

The arteriolar smooth muscle normally displays a state of partial constriction

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15
Q

Why is vascular tone importany?

A

If the smooth muscle is in a contracted state, then the arteriole wall can contract or dilate - if it was fully dilated at rest, it could only constrict, not dilate further

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16
Q

What does vascular tone affect?

A

Radius of the vessel

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17
Q

What is meant by active hyperaemia?

A

when the blood flow to a specific tissue is matched to its needs and is regulated by chemical changes

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18
Q

What chemical changes can drive active hyperaemia?

A

Increased oxygen useage

Increase metabolites

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19
Q

What affect does active hyperaemia ave on the arteries?

A

causes them to vasodilate

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20
Q

What is myogenic autoregulation?

A

When the blood flow to a particular organ is matched by its needs, and is dependent on physical stimuli

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21
Q

What physical stimuli could trigger myogenic autoregulation?

A

A drop in blood temperature

Stretch in the artery wall due to higher blood pressure

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22
Q

What effect does myogenic autoregulation have on the arteries?

A

causes the arteries to constrict

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23
Q

Through what mechanism are the radii of arteries adjusted after a big meal?

A

Through active hyperaemia in the gut

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24
Q

Through what mechanism are the radii of arteries adjusted after a big meal?

A

Through active hyperaemia in the gut

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25
Q

What is the mean arteriole pressue?

A

93 mmHg

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26
Q

What happens to the flow of blood through an arteriole following a rapid increase?

A

When the flow increases, so does the stretch on the arterioles

Therefore, this physical stimuli is detected by the arterioles, which then response through auto-regulation to bring the flow back to normal

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27
Q

What is the skeletal muscle arteriolar response to exercise?

A

Active hyperaemia

28
Q

What is the small intestine arteriolar response to exercise?

A

Myogenic vasoconstriction

29
Q

The radii of the arterioles are adjusted independently to accomplish which two functions?

A
  1. Match blood flow to the metabolic needs of the tissue

2. Help regulate systemic arterial blood pressure

30
Q

Through what two mechanisms do the aterioles help regulate arterial blood pressure?

A

Hormonal and Neural

31
Q

How does the neural control of blood vessel radii occur?

A

The cardiovascular control center in the medulla sends signals to vasocontrict to increase blood pressure

32
Q

Which hormones are involved in vasoconstriction?

A

Vasopressin/ADH
Angiotensin II
Adrenaline/noradrenaline

33
Q

What happens to the pressure gradient when there is vasoconstriction?

A

It decreases

34
Q

Where can the greatest pressure drop in the CVS be observed

A

From one end of the arteriole to the other

35
Q

What is the equation linking mean arterial pressure, cardiac output and total peripheral resistance?

A

MAP = CO x TPR

36
Q

What is the purpose of capillary exchange?

A

The delivery of metabolic substrates to the cells of the organisms

37
Q

What is the lumen diameter of a capillary?

A

7 micrometers

38
Q

What is the cell width of a capillary?

A

1 micrometer

39
Q

What are capillaries specially designed to do?

A

Minimise the diffusion distance

Maximise the surface area and time for diffusion

40
Q

Which tissues have highly dense capillary networks?

A

More metabolically active tissues

41
Q

Which tissue has a large capacity but limited flow at rest?

A

Skeletal muscle

42
Q

Why does the lung have such a dense capillary network?

A

Because of gas exchange which occurs in the lungs

43
Q

What percentage of arterioles are active at rest in skeletal muscle?

A

10%

44
Q

What happens to the arterioles during exercise in sketeal muscle?

A

They vasodilate due to active hyperaemia

45
Q

What is the definition of bulk flow?

A

A volume of protein-free plasma filters out of the capillary, mixes with the surrounding interstitial fluid and is then reabsorbed

46
Q

What is the difference in CO of skeletal muscle when at rest and during exercise?

A

It increases by 5x

47
Q

What are the very small gaps between endothelial cells in continuous capillaries called?

A

H2O filled gap junctions

48
Q

What substances can move across the H2O filled gap junctions?

A

Very smal molecules like sodium ions

49
Q

What are fenestrated capillaries?

A

Where you have little gaps/holes in the capillaries

50
Q

Where are fenestrated capillaries found?

A

In the glomerulus, intestinal vili and endocrine glands

51
Q

What are some tissues in which continuous capillaries are found?

A

Fat
Muscle
Nervous System

52
Q

In which capillary can glucose pass thorough the wall without the need for glucose transporters?

A

Fenestrated capillaries

53
Q

What are discontinuous capillaries?

A

Where there are large caps in the endothelial cells to allow large molecules to pass through?

54
Q

Where might you find discontinuous capillaries?

A

In the liver, bone marrow and spleen

55
Q

What type of capillary structure forms the blood brain barrier?

A

Continuous, without water filled gap junction

56
Q

What force pushes plasma out the capillary?

A

Hydrostatic pushing force

57
Q

What force causes plasma to be reabsorbed?

A

Oncotic pulling force - causes plasma to be reabsorbed

58
Q

What acts as an oncotic force to pull plasma back into the capillaries?

A

Proteins in the blood

59
Q

What determines transudation of fluids?

A

Capillary pressure

60
Q

What occurs if pressure inside the capillaries was greater than in the interstitial fluid?

A

Ultrafiltration

61
Q

What occurs if inward driving pressures are greater than outward pressures across the capillaries?

A

reabsorption

62
Q

What is the significance of the fact that ultra-filtration is more effective than reabsorption?

A

More fluid is lost into the surrounding tissue than is gained - therefore the excess fluid which is lost is picked up by lymphatic vessels and returned to circulation to maintain blood pressure

63
Q

What drives the lymphatic system given there is no central pump?

A

Pressure differences (results in flow)

64
Q

Where do the lymphatics drain into?

A

Into the right lymphatic duct and thoracic duct

65
Q

How much Lymph is drained a day?

A

3L

66
Q

What occurs if the rate of lymph production is greater than the rate of lymph drainage?

A

Oedema - swelling due to interstitial fluid buildup

67
Q

What is elephantiasis?

A

A parasitic disease which arises due to the blockage of lymph nodes, meaning there is no flow of fluid, gets trapped in the blood vessels

Cvr (13 decks)

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