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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
Q

If resistance changes, what else changes

A

Flow and pressure differences will change

Flow changes by n^4

26
Q

Poiseuilles Law

A

R= 8VL/πr^4

27
Q

What happens when diameter changes

A

Large resistance and flow changes

28
Q

What is flow proportional to

A

r^4

29
Q

What is resistance proportional to

A

1/r^4

30
Q

What is viscosity and how does it affect blood flow

A

More viscous, more thick

Blood is a non Newtonian fluid

31
Q

What is laminar flow

A

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
Q

How does blood flow through the capillaries and why

A

RBC 7um diameter
Capillaries 6um diameter
Ensures more contact, more O2 diffusion
V deformable cells, slip easily through, viscosity similar to plasma

33
Q

How does turbulence arise

A

High velocity movement

Sharp edges, branch points especially in large tubes disrupt laminar flow, cause vibrations

34
Q

The effects of greater turbulence

A

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
Q

How does flow change in distensible vessels as pressure increases

A

As pressure increases, flow increases in a linear manner

At a certain point, small increases in pressure lead to massive increases in flow

36
Q

How does flow change in rigid Poiseuille tubes as pressure increases

A

Direct linear relationship between flow and pressure

37
Q

How does flow change in distensible vessels with myogenic tone as pressure increases

A

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
Q

How does resistance change in a series circuit

A

R total = R1 + R2 + …

39
Q

How does resistance change in a parallel circuit

A

1/R total = 1/R1 + 1/R2 + …

40
Q

Control of organ blood flow

A

Changing perfusion pressure changes flow

Blood flow through organs/tissues regulated independently by resistance regulation

41
Q

What happens in a parallel circuit when P1-P2 is constant but the resistance in resistance arteries in 1 tissue increases

A

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
Q

What happens in a parallel circuit when P1-P2 is variable but the resistance in the resistance arteries in 1 tissue increases

A

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
Q

What is the mean arterial blood pressure equation

A

MABP=COxTPR

TPR controls arteriole radius

44
Q

Resistance and pressure in aorta

A

Large artery, low R
Diastolic pressure determined by resistance
CO > afterload

45
Q

Resistance and pressure in arteries and arterioles

A

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
Q

Resistance and pressure in arterioles to capillaries

A

Increased branching, increased R in parallel
Total R falls, P falls
Capillary pressure sufficient to maintain flow into venules

47
Q

Resistance and pressure in venues to veins

A

Fewer vessels in parallel, R rises
But diameter increases so R falls
Overall, P falls

48
Q

Overall resistance and pressure in pulmonary and systemic segments

A

Overall R and P lower in pulmonary than systemic

Principles of pharmacology and physiology (25 decks)

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