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nuero > cardiorespitory mechanics > Flashcards

cardiorespitory mechanics Flashcards

1
Q

what drives circulation in the rapid ejection part of the cardiac ejection

A

postive prressure

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2
Q

what causes heart sounds (s1 and s2)

A

SOUNDS OF VALVE CLOSING

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3
Q

what causes air to enter the lungs

A

diaphragm pulls down

decrease in thoracic pressure

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4
Q

what happens if you have a larger snokel

A

increase dead space

(increase distance from gas exchnage and ambient air)§

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5
Q

describe the relationship between reistance and radius

A

Resistance is inversely proportional to the fourth power of the radius
up to generation 4 the resistance to flow increase then decreases

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6
Q

Why doesn’t resistance continue to increase as airways get smaller?

A

although the airways get smaller, the amount of air decreases
lots of airways

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7
Q

relationship between lung volume and resistance

A

As the lung expands, the diameter of these vessels increases via radial traction of the vessel walls. Therefore, vascular resistance is low at large lung volumes. During lung collapse, there is increased resistance through the vessels due to the unopposed action of vessel elasticity.

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8
Q

what is Poiseuille’s Law

A

𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒= 8ƞƖ /𝜋𝑟^4

  1. Fluid viscosity (ƞ, eta)
  2. The length of the tube (L).
  3. Inner radius of the tube
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9
Q

does the cinductivity of airways increase or decrease with volume

A

The ‘conductivity’ of the airways increases with increasing volume

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10
Q

what happens as the lung volume increases to airway size

A

Airways are not rigid pipes – they dilate as lung volume increases

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11
Q

what is the organistaion of vessels including viens arterie ect

A 
arteries 
arteioles 
cappilliries 
venules 
veins
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12
Q

describe the change in surface are

A

increases to max at capiliry to then decrease

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13
Q

describe the mean pressure changes

A

pressure highest at arteries
massive reduction at atreioles
then decreases steadily

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14
Q

describe change in proportion of systemic volume

A

low at arteries
reduces more to capilies
then increases from venules to vein

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15
Q

which vessles are more resistance to flow

A

Small arteries and arterioles present most resistance to flow.

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16
Q

how does the pressure change accros ciruclation from systemic to pulmanory

A

Pressure falls across the circulation due to viscous (frictional) pressure losses.
high at systemic cos to push to whole body
low at pulmonary as only to lungs

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17
Q

how do arteries/arterioles regulate diameter

A

Small arteries and arterioles have extensive smooth muscle in their walls to regulate their diameters and the resistance to blood flow

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18
Q

why do veins act as a high resevior of blood

A

Veins and venules are highly compliant and act as a reservoir for blood volume

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19
Q

equation of blood pressure

Haemodynamic determinants of blood pressure

A 
Blood pressure (MAP)
= Cardiac output * Resistance
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20
Q

what are the key assumptions

A

steady flow (which does not occur due to the intermittent pumping of the heart)
rigid vessels
right atrial pressure is negligible
so only an approximate

21
Q

how is regulation of blood achieved

A

Physiologically, regulation of flow is achieved by variation in resistance in the vessels while blood pressure remains relatively constant.

22
Q

what is LAMINAR FLOW

A

flow in the same direction

Velocity of the fluid is constant at any one point and flows in layers

23
Q

where does the blood flow the fastest

A

Blood flows fastest closest to the centre of the lumen.

24
Q

slowest

A

towards the edge

25
Q

TURBULENT FLOW

A

Blood flows erratically, forming eddys, and is prone to pooling
Associated with pathophysiological changes to the endothelial lining of the blood vessels..

26
Q

what can be heard during deflation of the blood pressure cuff

A

Slow deflation of cuff causes turbulent flow which can be heard with a stethoscope

27
Q

how to work out plse pressure

A

SBP-DBP

28
Q

how to work out mean arterial pressure

A

DBP +1/3 pulse p

29
Q

what causes the dichrotic notch

A

caused by closure of aortic valve

30
Q

why do we have cartilangous airways

A

stop the airway collapsing in on its self
hard expiration should theoritcally cause our lung to collapse
This is why our large extrapulmonary airways are supported with cartilage

31
Q

what is compliance

A

The tendency to distort under pressure

if it isvery compliant a small pressure causes a large change in volume so steep volume pressure line
𝑪𝒐𝒎𝒑𝒍𝒊𝒂𝒏𝒄𝒆= ∆𝑽/∆𝑷

32
Q

elastance

A

The tendency to recoil to its original volume
high elastance means
small volume change requires large ellastance
𝑬𝒍𝒂𝒔𝒕𝒂𝒏𝒄𝒆= ∆𝑷/∆𝑽

33
Q

what is the difference in pressure changes once the aortic valve closes

A

Once the aortic valve closes (A) ventricular pressure falls rapidly but aortic pressure falls slowly

34
Q

why

A

This can be explained by the elasticity of the aorta and large arteries which act to “buffer” the change in pulse pressure.
The elasticity of a vessel is related to its compliance.

35
Q

how are the arteries able to change a pulsiatile flow into a constant flow

A

During ejection, blood enters the aorta and other downstream elastic arteries faster than it leaves them
When the aortic valve closes, ejection ceases but due to recoil of the elastic arteries, pressure falls slowly and there is diastolic flow in the downstream circulation
(recoil of arteries)

36
Q

If arterial compliance decreases (e.g. as arteries become stiffer with age). How would you expect blood pressure measurements to change?

A

remember blood pressure is 2 readings
systolic and diastolic

systolic increases - as the vessels will not stretch
diastolic decreases as the is no recoil pushing the blood

37
Q

what are 2 Facilitated venous return mechanisms

A

skeletal muscle pump

respitory pump

38
Q

Incompetent valves cause

A 
dilated superficial veins in 
the leg (varicose veins)
39
Q

Prolonged elevation of venous pressure (even with intact compensatory mechanisms) causes

A

oedema in feet/lower limbs

40
Q

what is Aneurysmal disease

A

Over time, vessel walls can weaken causing a balloon-like distension

Pathological example of the Law of Laplace. Vascular aneurysms increase radius of the vessel. This means that for the same internal pressure, the inward force exerted by the muscular wall must also increase.

However, if the muscle fibres have weakened, the force needed cannot be produced and so the aneurysm will continue to expand …
often until it ruptures

This pathology and the underlying physical forces involved also holds for the formation of diverticuli in the gut.

41
Q

when does venous compliance mean

A

its ability and willingness to change volume to a given pressure is greater than artery

42
Q

how do you increase venous pressure

A

Increasing smooth muscle contraction (green arrow) decreases venous volume and increases venous pressure.

43
Q

what is the ventilation differnce in the lung

A

ventilation at the base of the lung is greater than the top of the lung provided your standing up
head stand would cause it to invert

44
Q

and perfusion

A 
greater at the base 
Higher intravascular pressure 
(gravity effect)
More recruitment
Less resistance
Higher flow rate
45
Q

effective gas exchange requires

A

gas exchange occurs in the lungs between alveolar air and blood of the pulmonary capillaries. For effective gas exchange to occur, alveoli must be ventilated and perfused. Ventilation (V) refers to the flow of air into and out of the alveoli, while perfusion (Q) refers to the flow of blood to alveolar capillaries

46
Q

how does the ventialtion/perfusion ratio chnage from apex to base

A

decrease

47
Q

what is wasted ventilation

A

at the apex, the gas at the apex is not exchanged effictively as less perfusion

48
Q

what is wasted perfusion

A

at the base more blood going passed the respitory exchange surface than what can particpate in gas exchange

nuero (36 decks)

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