cardiorespitory mechanics

Question 1

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

Answer 1

postive prressure

Question 2

what causes heart sounds (s1 and s2)

Answer 2

SOUNDS OF VALVE CLOSING

Question 3

what causes air to enter the lungs

Answer 3

diaphragm pulls down

decrease in thoracic pressure

Question 4

what happens if you have a larger snokel

Answer 4

increase dead space

(increase distance from gas exchnage and ambient air)§

Question 5

describe the relationship between reistance and radius

Answer 5

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

Question 6

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

Answer 6

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

Question 7

relationship between lung volume and resistance

Answer 7

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.

Question 8

what is Poiseuille’s Law

Answer 8

𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒= 8ƞƖ /𝜋𝑟^4

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

Question 9

does the cinductivity of airways increase or decrease with volume

Answer 9

The ‘conductivity’ of the airways increases with increasing volume

Question 10

what happens as the lung volume increases to airway size

Answer 10

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

Question 11

what is the organistaion of vessels including viens arterie ect

Answer 11

arteries 
arteioles 
cappilliries 
venules 
veins

Question 12

describe the change in surface are

Answer 12

increases to max at capiliry to then decrease

Question 13

describe the mean pressure changes

Answer 13

pressure highest at arteries
massive reduction at atreioles
then decreases steadily

Question 14

describe change in proportion of systemic volume

Answer 14

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

Question 15

which vessles are more resistance to flow

Answer 15

Small arteries and arterioles present most resistance to flow.

Question 16

how does the pressure change accros ciruclation from systemic to pulmanory

Answer 16

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

Question 17

how do arteries/arterioles regulate diameter

Answer 17

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

Question 18

why do veins act as a high resevior of blood

Answer 18

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

Question 19

equation of blood pressure

Haemodynamic determinants of blood pressure

Answer 19

Blood pressure (MAP)
= Cardiac output * Resistance

Question 20

what are the key assumptions

Answer 20

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

Question 21

how is regulation of blood achieved

Answer 21

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

Question 22

what is LAMINAR FLOW

Answer 22

flow in the same direction

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

Question 23

where does the blood flow the fastest

Answer 23

Blood flows fastest closest to the centre of the lumen.

Question 24

slowest

Answer 24

towards the edge

Question 25

TURBULENT FLOW

Answer 25

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

Question 26

what can be heard during deflation of the blood pressure cuff

Answer 26

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

Question 27

how to work out plse pressure

Answer 27

SBP-DBP

Question 28

how to work out mean arterial pressure

Answer 28

DBP +1/3 pulse p

Question 29

what causes the dichrotic notch

Answer 29

caused by closure of aortic valve

Question 30

why do we have cartilangous airways

Answer 30

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

Question 31

what is compliance

Answer 31

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

Question 32

elastance

Answer 32

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

Question 33

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

Answer 33

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

Question 34

why

Answer 34

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.

Question 35

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

Answer 35

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)

Question 36

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

Answer 36

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

Question 37

what are 2 Facilitated venous return mechanisms

Answer 37

skeletal muscle pump

respitory pump

Question 38

Incompetent valves cause

Answer 38

dilated superficial veins in 
the leg (varicose veins)

Question 39

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

Answer 39

oedema in feet/lower limbs

Question 40

what is Aneurysmal disease

Answer 40

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.

Question 41

when does venous compliance mean

Answer 41

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

Question 42

how do you increase venous pressure

Answer 42

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

Question 43

what is the ventilation differnce in the lung

Answer 43

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

Question 44

and perfusion

Answer 44

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

Question 45

effective gas exchange requires

Answer 45

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

Question 46

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

Answer 46

decrease

Question 47

what is wasted ventilation

Answer 47

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

Question 48

what is wasted perfusion

Answer 48

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