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Principles of pharmacology and physiology > Flow and Pressure > Flashcards

Flow and Pressure Flashcards

1
Q

Definition of venous return

A

Volume/min into heart (5L/min)

Must equal cardiac output

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2
Q

Definition of central venous pressure

A

Filling pressure (preload) of right heart

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3
Q

Definition of stroke volume

A

Volume/beat (70mls)

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4
Q

Definition of cardiac output

A

Volume/min (5L/min)

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5
Q

Definition of total peripheral resistance

A

Pressure load on left heart, resistance to flow (afterflow)

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6
Q

Definition of axial streaming

A

Where the largest molecules flow in the center to reduce viscosity
Slowest flow occurs at sides of tubes

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7
Q

Why do we need a cardiovascular system

A

Rate of diffusion too slow to sustain life (O2, CO2, nutrients)

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8
Q

Describe the circulatory system

A

2 pumps in the heart in series

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9
Q

Properties of the systemic circulation

A

High resistance and pressure (92mmHg)

Mostly in parallel with each other

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10
Q

Properties of pulmonary circulation

A

Low resistance and pressure (16mmHg)

In series with the systems

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11
Q

What is the flow into the heart

A

Volume/min, venous return (5L/min)

Must equal cardiac output

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12
Q

What is the flow out of the heart

A 
Stroke volume (70mls), volume per beat
Cardiac output (5L/min), volume per minute
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13
Q

What is the cardiac output equation

A

CO=SVxHR

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14
Q

What is the filling of the heart

A

Determined by central venous pressure (CVP)

Filling pressure=preload

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15
Q

What is the resistance to flow

A

Total peripheral resistance (TPR), determines pressure on left heart
Afterload
Found in arterioles

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16
Q

How are substances moved in the blood to the cells

A

Bulk flow

Passive diffusion

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17
Q

How does bulk flow work

A

Transport within blood/air due to pressure differences

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18
Q

How does passive diffusion work

A

Movement down con grad

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19
Q

What is Fick’s Law

A

Rate of diffusion= ∆C x A/∆x x solubility/√MX

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20
Q

What does Fick’s Law depend on

A

Area over which diffusion occurs (A)
Difference in conc of diffusing substances (∆C)
Distance over which it has to travel (∆x)

21
Q

What affects the diffusion of a substance

A

Temperature
Solubility
√molecular weight (√MX)

22
Q

What is diffusion proportional to

A

Conc gradient

Permeability

23
Q

Darcys Law

A

Flow = (P1-P2)/R

24
Q

If flow changes, what else changes

A

Pressure differences change too

Resistance does not change

25
If resistance changes, what else changes
Flow and pressure differences will change | Flow changes by n^4
26
Poiseuilles Law
R= 8VL/πr^4
27
What happens when diameter changes
Large resistance and flow changes
28
What is flow proportional to
r^4
29
What is resistance proportional to
1/r^4
30
What is viscosity and how does it affect blood flow
More viscous, more thick | Blood is a non Newtonian fluid
31
What is laminar flow
Viscous drag at tube sides slows fluid down Fastest flow in center, cells aligned here in axial streaming In small vessels, decreased viscosity in Fahraeus Lindqvist effect
32
How does blood flow through the capillaries and why
RBC 7um diameter Capillaries 6um diameter Ensures more contact, more O2 diffusion V deformable cells, slip easily through, viscosity similar to plasma
33
How does turbulence arise
High velocity movement | Sharp edges, branch points especially in large tubes disrupt laminar flow, cause vibrations
34
The effects of greater turbulence
Increased resistance, causes vibrations Increased velocity blood flow in narrow heart valves => murmurs Increased velocity air flow in narrow airway => wheezes Damages vessel walls, activation of clotting mechanism
35
How does flow change in distensible vessels as pressure increases
As pressure increases, flow increases in a linear manner | At a certain point, small increases in pressure lead to massive increases in flow
36
How does flow change in rigid Poiseuille tubes as pressure increases
Direct linear relationship between flow and pressure
37
How does flow change in distensible vessels with myogenic tone as pressure increases
As pressure increases, flow increases in a linear manner At a certain point, massive increases in pressure leads to very small increases in flow as muscles are actively contracting to maintain constant flow
38
How does resistance change in a series circuit
R total = R1 + R2 + ...
39
How does resistance change in a parallel circuit
1/R total = 1/R1 + 1/R2 + ...
40
Control of organ blood flow
Changing perfusion pressure changes flow | Blood flow through organs/tissues regulated independently by resistance regulation
41
What happens in a parallel circuit when P1-P2 is constant but the resistance in resistance arteries in 1 tissue increases
If resistance of 1 tissue rises in the resistance arteries, the overall flow will decrease The resistances and flows of the other tissues in the parallel circuit are unaffected Flow controlled independently of tissue by constriction/dilation of its blood vessel
42
What happens in a parallel circuit when P1-P2 is variable but the resistance in the resistance arteries in 1 tissue increases
Flow through capillaries from resistance arteries in 1 tissue will decrease To compensate for the decreased flow in 1 tissue, the others will increase the flow
43
What is the mean arterial blood pressure equation
MABP=COxTPR | TPR controls arteriole radius
44
Resistance and pressure in aorta
Large artery, low R Diastolic pressure determined by resistance CO > afterload
45
Resistance and pressure in arteries and arterioles
Branch into arterioles, diameter decreases, R increases Pressure differences increase, P falls Small changes in radius= large difference in R and pressure differences Arterioles, v important in total peripheral R and MABP control
46
Resistance and pressure in arterioles to capillaries
Increased branching, increased R in parallel Total R falls, P falls Capillary pressure sufficient to maintain flow into venules
47
Resistance and pressure in venues to veins
Fewer vessels in parallel, R rises But diameter increases so R falls Overall, P falls
48
Overall resistance and pressure in pulmonary and systemic segments
Overall R and P lower in pulmonary than systemic

Principles of pharmacology and physiology (25 decks)

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