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PSYCH > 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
What is the mean arteriole pressue?
93 mmHg
26
What happens to the flow of blood through an arteriole following a rapid increase?
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
27
What is the skeletal muscle arteriolar response to exercise?
Active hyperaemia
28
What is the small intestine arteriolar response to exercise?
Myogenic vasoconstriction
29
The radii of the arterioles are adjusted independently to accomplish which two functions?
1. Match blood flow to the metabolic needs of the tissue | 2. Help regulate systemic arterial blood pressure
30
Through what two mechanisms do the aterioles help regulate arterial blood pressure?
Hormonal and Neural
31
How does the neural control of blood vessel radii occur?
The cardiovascular control center in the medulla sends signals to vasocontrict to increase blood pressure
32
Which hormones are involved in vasoconstriction?
Vasopressin/ADH Angiotensin II Adrenaline/noradrenaline
33
What happens to the pressure gradient when there is vasoconstriction?
It decreases
34
Where can the greatest pressure drop in the CVS be observed
From one end of the arteriole to the other
35
What is the equation linking mean arterial pressure, cardiac output and total peripheral resistance?
MAP = CO x TPR
36
What is the purpose of capillary exchange?
The delivery of metabolic substrates to the cells of the organisms
37
What is the lumen diameter of a capillary?
7 micrometers
38
What is the cell width of a capillary?
1 micrometer
39
What are capillaries specially designed to do?
Minimise the diffusion distance | Maximise the surface area and time for diffusion
40
Which tissues have highly dense capillary networks?
More metabolically active tissues
41
Which tissue has a large capacity but limited flow at rest?
Skeletal muscle
42
Why does the lung have such a dense capillary network?
Because of gas exchange which occurs in the lungs
43
What percentage of arterioles are active at rest in skeletal muscle?
10%
44
What happens to the arterioles during exercise in sketeal muscle?
They vasodilate due to active hyperaemia
45
What is the definition of bulk flow?
A volume of protein-free plasma filters out of the capillary, mixes with the surrounding interstitial fluid and is then reabsorbed
46
What is the difference in CO of skeletal muscle when at rest and during exercise?
It increases by 5x
47
What are the very small gaps between endothelial cells in continuous capillaries called?
H2O filled gap junctions
48
What substances can move across the H2O filled gap junctions?
Very smal molecules like sodium ions
49
What are fenestrated capillaries?
Where you have little gaps/holes in the capillaries
50
Where are fenestrated capillaries found?
In the glomerulus, intestinal vili and endocrine glands
51
What are some tissues in which continuous capillaries are found?
Fat Muscle Nervous System
52
In which capillary can glucose pass thorough the wall without the need for glucose transporters?
Fenestrated capillaries
53
What are discontinuous capillaries?
Where there are large caps in the endothelial cells to allow large molecules to pass through?
54
Where might you find discontinuous capillaries?
In the liver, bone marrow and spleen
55
What type of capillary structure forms the blood brain barrier?
Continuous, without water filled gap junction
56
What force pushes plasma out the capillary?
Hydrostatic pushing force
57
What force causes plasma to be reabsorbed?
Oncotic pulling force - causes plasma to be reabsorbed
58
What acts as an oncotic force to pull plasma back into the capillaries?
Proteins in the blood
59
What determines transudation of fluids?
Capillary pressure
60
What occurs if pressure inside the capillaries was greater than in the interstitial fluid?
Ultrafiltration
61
What occurs if inward driving pressures are greater than outward pressures across the capillaries?
reabsorption
62
What is the significance of the fact that ultra-filtration is more effective than reabsorption?
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
What drives the lymphatic system given there is no central pump?
Pressure differences (results in flow)
64
Where do the lymphatics drain into?
Into the right lymphatic duct and thoracic duct
65
How much Lymph is drained a day?
3L
66
What occurs if the rate of lymph production is greater than the rate of lymph drainage?
Oedema - swelling due to interstitial fluid buildup
67
What is elephantiasis?
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

PSYCH (78 decks)

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