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Cardiovascular System > The Peripheral Circulation > Flashcards

The Peripheral Circulation Flashcards

1
Q

Features of capillaries

A

Specialise for exchange
Abundant
Thin walled
Small diameter (big SA to volume ratio)

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2
Q

Continuous capillaries

A

Muscle

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3
Q

Fenestrated capillaries

A

Intestines or kidneys

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4
Q

Discontinuous capillaries

A

Liver

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5
Q

Features of diffusion (4)

A

Self-regulating
No-saturable
Non-polar substances across membrane
Polar substances through channels

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6
Q

Example of carrier-mediated transport

A

Glucose transporter

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7
Q

Where can glucose transporters be found

A

Capillaries of the brain

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8
Q

What does capillary hydrostatic pressure do

A

Pushes water out through leaky capillaries

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9
Q

What is the effect of the water being pushed out the capillaries

A

Mainly proteins remain in the capillary and fluid moves back through osmotic pressure

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10
Q

Net filtration pressure =

A

(Capillary hydrostatic pressure - tissue interstitial hydrostatic pressure) - (Plasma colloid osmotic pressure - interstitial fluid colloid osmotic pressure)

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11
Q

Overall how much is lost and regained each day

A

20L lost

17 L regained

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12
Q

What happens to the remaining 3L

A

Picked up by lymphatic system and fed back through the CV system

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13
Q

What can happen if the lymphatic system becomes overwhelmed

A

Oedema

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14
Q

What is Oedema

A

Accumulation of excess fluid

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15
Q

What causes Oedema (4)

A

Lymphatic obstruction
Raised CVP
Hypoproteinaemia
Increased capillary permeability- inflammation

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16
Q

Darcy’s Law

A

Flow = Pressure/ Resistance

17
Q

MAP - CVP (usually low or 0) =

A

CO X TPR

18
Q

Poiseuille’s (4)

A 
Flow rate is dependent on:
Pressure 
Radius
Fluid viscosity
Length of tube
19
Q

Why is resistance juggling important

A

Balance between blood flow to individual vascular beds and MAP need to be kept

20
Q

How is resistance juggling achieved

A

Intrinsic and Extrinsic mechanisms

21
Q

What is Intrinsic mechanism

A

Concerned with meeting the selfish needs of each individual tissue to meet its metabolic needs

22
Q

Mechanisms of Intrinsic response (3)

A

Active (metabolic) hyperaemia
Pressure flow autoregulation
Reactive hyperaemia

23
Q

Active (metabolic) hyperaemia (3)

A

Increase in metabolic activity causes increase in metabolites
Triggers release of EDRF/NO
This causes arteriolar dilation
Increased flow washes out metabolites

24
Q

Pressure Flow Autoregulation (4)

A

Decrease in MAP causes decrease in flow
Metabolites accumulate
Triggers release of EDRF/NO
Arterioles dilate

25
Q

Reactive Hyperaemia (7)

A 
Injury
Release of substance P
Mast cell and Histamine release
Arteriolar dilation
Increase in blood supply
Increase in permeability
Aids delivery of blood borne leukocytes to injured area
26
Q

What is extrinsic mechanism

A

Concerned with ensuring that the total peripheral resistance (therefore MAP) of the whole body stays regulated and comes from outside (hormonal/neural)

27
Q

Neural Extrinsic (4)

A

Sympathetic nerve release noradrenaline
Binds to alpha 1 receptors
Causes arteriolar constriction
Decreases flow and increases TPR

28
Q

Hormonal Extrinsic (4)

A

Adrenaline released from adrenal medulla
Binds to alpha1 receptors
Causes arteriolar constriction
Decreases blood flow and increases TPR

29
Q

What receptors does the hormones activate and what does that cause (3)

A

B2 in skeletal and cardiac
Causes arteriolar dilation
Increased flow and decreases TPR

30
Q

Coronary Circulation (3)

A

Blood supply of heart is interrupted during systole
Expresses many B2 receptors which swamp any sympathetic arteriolar constriction
Hyperaemia

31
Q

Cerebral Circulation (2)

A

Needs to be kept stable

Shows excellent pressure autoregulation

32
Q

Pulmonary Circulation

A

Decrease in O2 causes arteriolar constriction- shunt

33
Q

What is the purpose of a shunt

A

To ensure blood is directed to the best ventilated part of the lung

34
Q

Renal circulation

A

Main function is filtration which depends on pressure

35
Q

Decrease in renal circulation (extreme)

A

Swelling

36
Q

Increase in renal circulation (extreme)

A

Shrinkage

Cardiovascular System (42 decks)

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