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BRS 6: Cardiovascular And Respiratory Medicine > 6.6: Microcirculation > Flashcards

6.6: Microcirculation Flashcards

(59 cards)

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1
Q

Calculation for pressure gradient to work out blood flow to capillary

A

(P) = pressure A - pressure B
(Pressure A - arteriolar pressure)
(Pressure B - capillary network pressure)

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2
Q

Overall aim of cardiovascular system is

A

Adequate blood flow through capillaries

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3
Q

Blood flow rate is

A

Volume of blood passing through a vessel per unit time

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4
Q

Darcys law calculation and calculating flow rate

A

( P = Q x R )
Q = P/R (flow rate = pressure / resistance)

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5
Q

What does an Increase in pressure gradient do to the flow rate

A

Increases flow rate

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6
Q

Resistance (R) is

A

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

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7
Q

3 factors affecting resistance

A

Vessel length
Vessel radius
Blood viscosity

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8
Q

Impact of vessel radius on resistance

A

Vessel radius can change rapidly, therefore has the greatest impact on resistance
Halving radius decreases flow x16

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9
Q

What happens to pressure gradient as blood pressure increases

A

Pressure increases

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10
Q

What happens to pressure during arteriolar vasoconstriction

A

Remains the same

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11
Q

What happens to resistance during increased blood pressure

A

Stays the same

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12
Q

What happens to resistance during arteriolar vasoconstriction

A

Resistance increases

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13
Q

What happens to flow as blood pressure increases

A

Flow increases

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14
Q

What happens to flow during arteriolar vasoconstriction

A

Flow decreases

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15
Q

Calculation of blood flow or any organ

A

Blood flow = change in pressure/ resistance against entire organ

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16
Q

What would happen without a pressure difference to the blood

A

Blood would not reach tissue capillary beds

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17
Q

How does vasoconstriction affect radius, resistance and flow

A

Radius decreases
Resistance increases
Flow decreases

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18
Q

How does vasodilation affect radius, resistance and flow

A

Radius increases
Resistance decreases
Flow increases

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19
Q

Why is it important for smooth muscle to display a state of partial constriction (vascular tone)?

A

Vascular tone allows for dilation and constriction to regulate blood flow

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20
Q

Why are the radii of arterioles adjusted independently

A

To accomplish two functions :
Match blood flow to metabolic needs of specific tissues
Help regulate systemic arterial blood pressure

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21
Q

What is matching blood flow to metabolic needs regulated by

A

Local (intrinsic) controls, and independent of nervous or endocrine stimulation

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22
Q

What is regulating systemic arterial blood pressure controlled by

A

Extrinsic controls which travel via nerves or blood and are usually centrally coordinated

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23
Q

What is active hyperaemia

A

Tissue starts working harder:
Increased metabolites and O2 usage
Vasodilation of arterioles
-chemical

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24
Q

What is myogenic autoregulation

Study These Flashcards
A

E.g twisting ankle
Aim is to induce vasoconstriction
Decrease blood temperature
Increase stretch (distension) due to increased blood pressure
Decrease blood flow

25
What is stretch distension due to increased blood pressure
Pressure gradient across every micro circulation increases In tissues which are not being used- autoregulation occurs as increase in arteriole pressure is detected: arterioles constrict to regulate blood flow Allowing blood flow to heart, brain, lungs
26
Skeletal muscle arterioles during exercise undergo
Active hyperaemia
27
Small intestines arterioles during excersise undergo
Myogenic vasoconstriction
28
Equation for flow across whole circulation
Cardiac output (flow)= blood pressure/total peripheral resistance
29
How is blood pressure regulated in many tissue beds at once
Cardiovascular centre in medulla sends signal via sympathetic nervous system which innervates arterioles and causes them to constriction
30
Why does blood flow to specific organs decrease as arterial blood pressure is regulated within the body
Baroreceptors detect decrease in blood pressure, decreasing flow to blood vessels as vasoconstriction occurs only in specific tissues which preserve blood pressure
31
3 Hormones that control and regulate arterial blood pressure
Vasopressin Angiotensin Adrenaline Leading to vasoconstriction
32
Why is capillary density important
Ideally suited to enhance diffusion Specially designed to minimise diffusion distance and maximise surface area and time for diffusion
33
What is the purpose of capillary exchange
Delivery of metabolic substrates to the cells of the organism - ultimate function of CVS
34
Capillary networks in highly metabolically active tissues
Denser capillary network (e.g lung has the highest capillary network to allow most gas diffusion, followed by myocardium/brain and skeletal muscle)
35
Biggest tissue in body, and it’s characteristic of blood flow
Skeletal muscle Huge capacity but limited flow at rest
36
Continuous capillary structure
Single file endothelial cells with water filled gap junctions between them Small molecules able to pass through gaps
37
Fenestrated capillary structure
Endothelial cells have greater gaps between them allowing larger molecules to pass through e.g gut
38
Discontinuous capillary structure
Larger gaps between endothelial cells E.g bone marrow and liver
39
What type of capillary is in the blood brain barrier
Continuous with no gap junctions
40
How does blood flow into and out of capillaries
Blood forced into capillary at high pressure due to hydrostatic force, some fluid is forced out of gaps between capillaries
41
What force pushes blood into capillaries
Hydrostatic pushing force
42
What force returns blood to the capillary
Oncotic pulling force (osmotic)
43
Bulk flow hypothesis
Volume of protein free plasma filters out of capillary, mixes with surrounding interstitial fluid (IF) and is reabsorbed
44
Starlings hypothesis
Net fluid movement - hydrostatic pressure and oncotic pressure
45
What occurs when the pressure inside the capillary is greater than in the IF
Ultrafiltration
46
What occurs when the inward driving pressures exceed the outward pressures across the capillary
Reabsorption
47
What is the significance of ultrafiltration being more effective than reabsorption
Role of lymphatic system
48
Role of lympathic system
Venous return - in one direction Lymphatic capillaries collect tissue fluid and return it to circulation
49
Where does the lymphatic system connect to the circulation
Right lymphatic duct - thoracic duct Right and left subclavian vein
50
Main characteristic of lymphatic system
No pump to induce flow 3L of fluid returned per day
51
Why do lymph nodes swell during illness
Bacteria and virus in tissue fluid passes through lymph nodes, immune system activated in nodes, swelling occurs and bacteria and viruses targeted
52
When does oedema ensure
When rate of production is greater than rate of drainage
53
Elephantiasis is
Parasitic blockage of lymph nodes
54
Characteristics of lymphatic system
Blind - ended, single-layered and contain large permeable water filled one way channels
55
What is capillary density proportional to
Metabolic activity
56
Arterioles are the
Major resistance vessels
57
Intrinsic factors affecting arterioles
Chemical and physical (metabolic activity and stretch) to match blood flow to needs
58
Intrinsic factors affecting atterioles
Neural and hormonal (SNS activity and adrenaline) to regulate arterial blood pressure
59
Smooth muscle tone affects
Radius, which affects flow

BRS 6: Cardiovascular And Respiratory Medicine (12 decks)

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