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Cardiovascular physiology > Vascular physiology > Flashcards

Vascular physiology Flashcards

1
Q

Why is diffusion inadequate for delivering solutes to cells of large organisms?

A

Diffusive distance too large so substsantial diffusive delay

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2
Q

What is the limit for an organisms size that can be served by diffusion only?

A

100 microns

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3
Q

What influences diffusion time?

A

Distance travelled squared is proportional

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4
Q

Describe curve of distance vs diffusion time graph

A

Flat then exponential beyond 1mm

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5
Q

What is bulk flow?

A

Movement of medium and the solutes it contains

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6
Q

What does bulk flow distribute?

A

Substrates, waste products, signals e.g. hormones, heat and pressure

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7
Q

What is the benefit of bulk flow?

A

Overcomes diffusional limitations and works over long distances

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8
Q

How do you work out time for transport of bulk flow?

A

Distance travelled/velocity

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9
Q

What is the velocity of bulk flow?

A

2m/sec

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10
Q

Describe curve for distance vs time required for bulk flow

A

Linear through origin

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11
Q

What enhances bulk flow?

A

Reduced resistance, therefore, wide tubes and low fluid viscosity

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12
Q

Why is left side of heart generating 6 times the pressure of right side?

A

Systemic circulation is 6 times greater in resistance than pulmonary, as the resistance is 6x higher, so to keep same flow, need 6x higher pressure

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13
Q

In a single pump system, what happens as distance from source increases?

A

Lose energy, mean pressure falls and downstream tissues perfused at lower pressure

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14
Q

Describe the curve for blood velocity

A

Greatest in arteries, decreases going through arterioles and lowest in capillaries, then increases again in veins

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15
Q

What is blood velocity through blood vessels inversely proportional to?

A

Cross sectional area of vessel

i.e. capillaries have greatest cross sectional area and lowest blood velosity

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16
Q

Which vessels hold the most blood and why?

A

Veins, they are the most compliant

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17
Q

Describe the proportion of blood held in different vessels

A 
Vein 70%
Systemic Artery <10%
Systemic capillaries <5%
Lungs 10%
(Note 10% in heart)
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18
Q

How does flow remain the same throughout circulation through different vessels?

A

Decrease in velocity as you branch into capillaries but cross sectional area increases so flow (velocity x cross sectional area) constant through circulation

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19
Q

How is flow calculated?

A

Change in volume/time (L/min)

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20
Q

Cardiac output is an example of

A

Flow

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21
Q

Example of conservation of flow

A

Flow in systemic circulation = flow in pulmonary circulation

i.e. larger volume in systemic circulation but circulation takes longer

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22
Q

What happens if there isnt conservation of flow?

A

Blood pools in either circuit

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23
Q

What happens to flow as cross sectional area increases by factor of 3, why?

A

Velocity decreases by 3, flow stays the same

24
Q

Equation for pressure

A

Pressure = force/area

25
Q

What happens to pressure as distance from heart increases?

A

Fluctuations in pressure decrease from aorta to arterioles and stop in capillaries and veins

Pressure gradually decreases (50mmHg in arterioles and 20mmHg in capillaries)

26
Q

Where is the pressure constant (which vessels don’t have pulsatile flow)?

A

Capillaries and veins

27
Q

Equation for compliance

A

Change in volume over change in pressure

28
Q

What is the relationship between vessel radius and resistance to flow?

A

Doubling radius increases resistance to flow by 2^4 I.e. 16

29
Q

What are the units for blood pressure?

A

mmHg

30
Q

How do you work out pulse pressure?

A

Systolic bp - diastolic bp

31
Q

What is normal pulse pressure?

A

40mmHg

32
Q

What is normal mean arterial pressure?

A

70-110mmhg (93mmHg)

33
Q

Compare pulse pressure in stiff and normal arteries, why is it like this

A

Smaller pressure differences as stroke volume increases in normal artery (vessels more elastic)
But: stiffer arteries, greater extremes of pressure

34
Q

What is the central venous pressure?

A

Blood pressure in the vena cavae near right atrium of heart (reflects amount of blood returning to heart + ability of heart to pump blood back into arterial system

35
Q

What is normal CVP?

A

5mmHg

36
Q

How is CVP measured?

A

JVP provides indirect measure of CVP:

Patient lies at 45degrees
Filling level (height of column of blood) of external jugular vein determined
37
Q

What is JVP?

A

Pressure in the jugular vein

38
Q

Describe normal stroke volume and heart rate at rest

A

70ml and 70bpm

39
Q

What is the relationship between arterial and venous pressure, cardiac output and total peripheral resistance?

A

MAP-CVP=CO x TPR

40
Q

What is normal cardiac output?

A

5l /min

41
Q

Describe what we use sphygmomanometer for?

A

To measure blood pressure, the cuff is placed around the bare and stretched out upper arm, and inflated until pressure exceeds systolic pressure. Then the air is slowly let out of the cuff.

As soon as the air pressure in the cuff falls below the systolic blood pressure in the brachial artery, blood will start to flow through the arm once again. This creates a pounding sound when the arteries close again and the walls of the vessels hit each other after a heart beat (in diastole).

The sound can be heard by placing the stethoscope close to the elbow. Right when you start to hear this pounding for the first time you can read your systolic blood pressure off the pressure meter.

The pounding sound stops when the air pressure in the cuff falls below the diastolic blood pressure in the brachial artery. Then the blood vessels remain open. Right when the pounding stops, you can read the diastolic blood pressure off the pressure meter.

42
Q

What causes k sounds?

A

Blood flows in spurts as pressure in artery greater than cuff pressure then drops below cuff pressure causing turbulence and K sound.

43
Q

Compare and contrast the volume vs pressure (i.e. compliance) curves for veins and arteries

A

Both linear lines through origin

Veins line steeper as they are are complaint

44
Q

Which vessels show the greatest resistance to flow?

A

Arterioles, causes blood to experience greatest drop in pressure.

45
Q

Describe relationship between viscosity and haematocrit

A

Linear

46
Q

Why is there not a linear relationship between viscosity and radius?

A

In microcirculation resistance is reduced as RBCs pass through in single file through low viscosity plasma stream,

47
Q

How does viscosity affect blood flow?

A

Viscosity increases, TPR increases, and blood flow decreases. (Inversely proportional between haematocrit and blood flow)

48
Q

Is pressure and flow linear relationship in vessels, why?

A

No, compliant vessels

49
Q

True of false, arterioles are first sight of vascular resistance

A

False, aorta albeit small resistance

50
Q

How does CVP change in the respiratory cycle?

A

Increases in respiration decreases in exhalation.

51
Q

Why do arteries need a thicker wall?

A

Greater tension needed to exert on blood to deal with greater pressure

52
Q

Mean systemic arterial pressure at the level of the heart, in a healthy individual at rest, is …

A

95 mm Hg (13 kPa)

53
Q

Cardiac output may be acutely increased by…

A

A fall of total peripheral vascular resistance

54
Q

A rise in blood haematocrit would increase peripheral vascular resistance?

A

True

55
Q

A competitive antagonist of alpha1 adrenoceptors?

A

Prazosin

Cardiovascular physiology (11 decks)

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