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CVS > Session 5 - Flow through tubes > Flashcards

Session 5 - Flow through tubes Flashcards

1
Q

What are high resistance vessels

A

Arterioles

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2
Q

What are low resistance vessels

A

Arteries

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3
Q

Why do the capillaries have overall low resistance

A

As they are connected in parallel

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4
Q

Define flow

A

The volume of fluid passing a given point per unit time
Flow = Volume/Time
Flow = Velocity X Area

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5
Q

Define Velocity

A

Rate of movement of particles along the tube at a given flow

Inversely proportional to the cross sectional area (if a tube is wide the velocity is slow)

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6
Q

What is laminar flow

A

Gradient of velocity from the edge to the middle, the middle being the fastest
Quiet
Flow in most vessels

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7
Q

What is turbulent flow

A

Happens as the mean velocity increases. Gradient of velocity breaks down
Can be heard (bruit)
Increase in flow resistance

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8
Q

What is viscosity

A

The extent to which layers of particles resist moving over each other

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9
Q

What factors affect flow resistance

A

Velocity - resistance increases as velocity increases

Radius - Resistance decreases with the 4th power of the radius

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10
Q

What is capacitance

A

The ability of vessels to store blood
Veins are the most distensible vessels and therefore have the greatest capacitance
More blood is flowing in than out as the walls are distensible

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11
Q

Where do blood cells congregate

A

In the middle of flow

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12
Q

What is systolic pressure

A

The maximal arterial pressure normally around 120mmHg

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13
Q

What is systolic pressure affected by

A

How hard the heart pumps
TPR
Compliance of arteries

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14
Q

What is diastolic pressure

A

Minimal arterial pressure normally around 80mmHg

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15
Q

What is diastolic pressure affected by

A

Systolic pressure

TPR

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16
Q

What is the difference between systolic and diastolic pressure called

A

Pulse pressure

17
Q

What is TPR

A

The total resistance of all the peripheral vessels in the systemic circulation

18
Q

What is vasomotor tone and what factors affect it?

A

Tonic contraction of smooth muscle
Affected by:
- sympathetic branch of ANS
- antagonised by vasodilator factors e.g. H+, K+ and adenosine

Resistance is a balance between the two

19
Q

What is CVP and what does it depend on?

A 
Central venous pressure = pressure in the great veins
Depends on:
-return of blood from body
-pumping of the heart
-gravity  and muscle pumping
20
Q

What is venous return

A

the rate of flow of blood back towards the heart

limits CO

CVS (6 decks)

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