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RESPIRATORY > Physiology > Flashcards

Physiology Flashcards

1
Q

what is internal respiration

A

inside cells

ATP & CO2 produced from glucose & O2

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2
Q

what is external respiration

A

exchange of O2 and CO2 with the external environment and body cells

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3
Q

4 steps of external respiration

A

1) ventilation
2) gas change between alveoli & blood in lungs
3) transport of O2 & CO2 in blood: lungs -> tissues
4) O2/CO2 exchange between blood and tissues (leads to internal respiration) in systemic capillaries & body cells

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4
Q

4 systems involved in external respiration

A

respiratory
cardiovascular
haematology
nervous

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5
Q

what is ventilation

A

gas exchange between alveoli & atmosphere

high -> low pressure

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6
Q

what happens during inspiration

A

contraction of inspiratory muscles
diaphragm moves down, dome flattens
intercostals move out
thorax & lungs expand

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7
Q

what happens to pressure in the lungs upon inspiration

A

intra-alveolar pressure is less than atmospheric pressure so air drawn into the lungs
pressure decreases

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8
Q

what happens as volume in which the gas is distributed in increases

A

pressure exerted by gas decreases

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9
Q

boyles law

A

at any constant temperature, pressure exerted by a gas varies inversely with the volume of the gas

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10
Q

what is pulmonary ventilation

A

volume of air breathed in and out per min

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11
Q

what increases pulmonary ventilation

A

exercise: increases depth (tidal volume) & increased breathing rate

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12
Q

calculation for pulmonary ventilation

A

L = tidal volume (L/breath) x respiratory rate (breath/min)

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13
Q

what is alveolar ventilation

A

volume of air exchanged by the atmosphere and alveoli per min
new air available for gas exchange

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14
Q

why is alveolar ventilation < pulmonary ventilation

A

dead space (some air not available for gas exchange)

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15
Q

equation for calculating alveolar ventilation

A

(tidal volume - dead space volume) x respiratory rate

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16
Q

why is alveolar ventilation more advantageous

A

increases depth of breathing

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17
Q

how is alveolar ventilation increased

A

deep slow breathing

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18
Q

how is pulmonary ventilation decreased

A

rapid shallow breathing

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19
Q

why is alveolar ventilation not completey perfused

A

due to dead space

hence air in alveoli not perfect match for blood in pulmonary capillaries

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20
Q

is dead space bad

A

dead space insignificant in heathy people as small

increases in disease

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21
Q

upon inspiration how much air is in the alveoli

A

150 already there as alveoli are never completely empuy

350 ml added

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22
Q

how are pleural membranes attached

A

water in intrapleural fluid attracted to each other so aren’t puled apart

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23
Q

what creates the pressure gradient in the lungs

A

sub-atmospheric intrapleaural pressure gradient

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24
Q

what does the intrapleaural gradient cause

A

lungs expand out, while chest squeezes in

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25
Q

what is pressure in the lung and pleura

A

lung = 760 mmHg (101 kPa)
pleura = 756 mmHg
lung pressure > pleura pressure

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26
Q

what is the transmural pressure gradient

A

4 mmHg

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27
Q

what are the 3 pressures I ventilation

A

intra - alveolar = 760 mmHG
atmospheric = 760 mmHg
Intrapleural = 756 mmHg

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28
Q

during ventilation what happens to the pressures in the lungs

A

intra-alveolar pressure pushes out (alveoli expand)

lower intra-pleura pressure pushes inwards

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29
Q

during ventilation what happens to the pressures in the thoracic cavity

A

atmospheric pressure pushes inwards

intrapleura pressure pushes out

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30
Q

what nerves keep the diaphragm alive

A

phrenic nerves C3,4,5

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31
Q

role of major inspiratory muscles

A

contract during normal quiet breathing

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32
Q

what are the major inspiratory muscles

A

diaphragm - increases thorax volume vertically

external intercostal muscles

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33
Q

how does the external intercostals increase lung volume

A

contracts to lift ribs, increases anterior and posterior, sternum moves out
increase thorax volume horizontally
bucket handle

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34
Q

role of the accessory inspiration muscles

A

contract only during forceful inspiration

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35
Q

3 types of accessory inspiration muscles

A

sternocleidomastoid
scalenus
pectoral

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36
Q

what is the role of the muscles of active expiration

A

only contract during forceful expiration

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37
Q

2 types of active expiration muscles

A

abdominal muscles

internal intercostal muscles

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38
Q

inspiration & expiration occurs against/down a pressure gradient

A

down

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39
Q

when does air enter/leave until

A

intra-alveolar pressure = atmospheric pressure

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40
Q

is inspiration active or passive

A

active (3% energy use)

inspiratory muscles contract

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41
Q

is expiration active or passive

A

passive

inspiratory muscles relax

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42
Q

process of inspration

A

diaphragm contacts, moves down, dome flattens, ribs move out

lungs increase siize/volume, intra-alveolar pressure decreases

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43
Q

process of expiration

A

diaphragm relax, dome resume, moves up

chest wall recoils, smaller volume, intra-alveolar pressure rises so airforces out

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44
Q

intra-alveolar and intra-pleural pressure during inspiration

A 
intra-alveolar = 759mmHg
intra-pleural = 754 mmHg
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45
Q

intra-alveolar and intra-pleural pressure during expiration

A 
intra-alveolar = 761 mmHg
intra-pleural = 756 mmHg
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46
Q

during inhalation what is the airways pulled open by

A

expanding thorax

intrapleural pressure falls

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47
Q

3 factors keeping alveoli open

A

transmural pressure gradient (MOST IMPORTANT) - sub-atmospheric
surfactant
alveolar interdependance

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48
Q

what creates the pressure gradient in the lungs

A

the difference between the pressure in the alveoli and the pleura
pleura pressure is always less than alveoli pressure

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49
Q

what is the role surfactant

A

reduces water surface tension
prevents lungs collapsing
prevents smaller alveoli emptying air into larger alveoli
interdespences meteen water molecules lining alveoli

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50
Q

what is surfactant made up of

A

lipids and proteins

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51
Q

surfactant has a bigger effect on smaller/bigger alveoli

A

smaller

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52
Q

what is surfactant secreted by

A

type II alveoli

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53
Q

define LaPlace Law

A

smaller alveoli = greater tendency to collape

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54
Q

LaPlace Law equation

A 
P = 2T / r
P = inward directed collapsing pressure
T = surface tension
r = alveoli radius
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55
Q

what is alveolar interdependence

A

if alveoli starts collapsing surrounding alveolar stretch then recoil expanding forces on collapsing alveolus opening it

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56
Q

what factors promote the alveoli to collapse

A

elasticity of stretched lung connective tissue (during recoiling)
alveolar surface tension (water molecules line alveoli)

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57
Q

what is tidal volume

A

0.5 L
normal quiet breathing
volume enter/leaves in 1 breath

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58
Q

what is inspiration residual volume

A

3.0 L
during laboured breath in
extra volume maximally inspired
above tidal volume

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59
Q

what is expiration residual volume

A

1.0 L
extra volume actively expired by maximal contraction after resting tidal volume
forcefully pushing air out

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60
Q

what is is residual volume

A

1.2 L
some air always remains in lungs
cannot be measured by spirometry

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61
Q

how is residual volume increased

A

when lung elastic recoil is lost eg. emohysema

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62
Q

what is inspiratory capacity

A

3.5 L
IRV + TV
max air that can be breathed in after normal quiet expiration

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63
Q

what is vital capacity

A

4.5 L
IRV + TV + ERV
max air that can be moved out during 1 breath after max inspiration
most important

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64
Q

what is Functional residual capacity

A

2.2 L
ERV + RV
air in lungs after normal passive expiration

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65
Q

what is total lung capacity

A

5.7 L
max volume lung can hold
VC + RV
cannot be measured by spirometry

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66
Q

what is dynamic airway compression

A

active expiration more difficult in patients with airway obstructions eg. asthma/COPD

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67
Q

what does dynamic airway compression a result of

A

driving pressure between alveolus and airway lost

rising pleural pressure compresses alveoli & airway

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68
Q

what does increased airway resistance cause

A

increased airway pressure = compressed airway

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69
Q

define pulmonary compliance

A

measure of the effort that goes into stretching/distending lungs

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70
Q

what causes decreased pulmonary compliance

A 
pulmonary fibrosis
pulmonary oedema
lung collapse
pneumonia
absence of surfactant
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71
Q

why is decreased pulmonary compliance not good

A

more effort required to inflate lungs
greater change in pressure need to meet lung volume target
stiffer lungs
shortness of breath

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72
Q

what is increased pulmonary compliance

A 
when elastic recoil of lungs is lost
by emphysema (worsened COPD)
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73
Q

why is increased pulmonary compliance not good

A

have to work harder to get air out off the lungs - hyperinflation
obstructed airways
increases with age

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74
Q

how can breathing be increased

A

decreased pulmonary compliance
airway resistance increased
elastic recoil decreased
need for increased ventilation

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75
Q

how full are the lungs usually during normal breathing

A

1/2 full

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76
Q

define ventilation

A

rate at which gas is passing through the lungs

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77
Q

define perfusion

A

rate at which blood is passing through the lungs

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78
Q

what is the hypothetical point at which air flow rate matches perfusion

A

1
volume of blood leaving the lungs has the same PO2 as alveoli
airflow = bloodflow

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79
Q

if there is lots of ventilation there is more/less perfusion

A

more

80
Q

what structures are involved in lung ventilation-perfusruin patch

A

airway smooth muscle + arterioles

81
Q

in an area with greater perfusion than ventilation CO2 decreases/increases and O2 increases/decreases

A

CO2 increases

O2 decreases

82
Q

in area with greater perfusion than ventilation airways dilate/constrict and local vessels constrict/dilate

A

airways - dilate

vessels - constrict

83
Q

in area with greater perfusion than ventilation airflow increases/decreases and blood flow increases/decreases

A

airflow increases

blood flow decreases

84
Q

in area with greater ventilation than perfusion airflow increases/decreases and blood flow increases/decreases

A

airflow decreases

blood flow increases

85
Q

in area with greater ventilation than perfusion airways dilate/constrict and local vessels constrict/dilate

A

airways constrict

vessels dilate

86
Q

in areas with greater ventilation than perfusion CO2 increases/decreases and O2 increases

A

CO2 deceases

O2 increases

87
Q

when there is decreased O2 pulmonary arterioles vasodilation/vasoconstriction

A

vasoconstriction

88
Q

when there is decreased O2 systemic arterioles vasodilation/vasoconstriction

A

vasodilation

89
Q

when there is increased O2 pulmonary arterioles vasodilation/vasoconstriction

A

vasodilation

90
Q

when there is increased O2 systemic arterioles vasodilation/vasoconstricition

A

vasoconstriction

91
Q

4 factors affecting gas exchange rate

A

partial pressure of O2 & CO2
diffusion coefficient of O2 & CO2
alveolar membrane SA
thickness of alveolar membrane

92
Q

how does pp O2 and CO2 affect gas exchange rate

A

high to low pp gradient
rate exchange increases when pp increases
most important factor

93
Q

how does the diffusion coefficient of O2 & CO2 affect gas exchange rate

A

transfer increases as coefficient increases

CO2 coefficient 20x O2 coefficient

94
Q

how does alveolar SA affect gas exchange rate

A

as SA increases gas exchange rate increases

95
Q

how alveolar membrane SA be increased

A

by exercise

96
Q

how can alveolar membrane SA be decreased

A

emphysema lung collapse

pneumoectomy

97
Q

what affect does increasing the alveolar membrane have on gas exchange rate

A

decreases as thickness increases

98
Q

how is the thickness of the alveolar membrane increased

A

by pulmonary oedema, fibrosis, pneumonia

99
Q

what determines pressure gradient

A

partial pressure

100
Q

define partial pressure

A

pressure one gas in a mixture would exert if occupied total volume (only gas present) at given temp

101
Q

define Daltons Law

A

total pressure entered thy gaseous mixture = sum of partial pressures of each individual component

102
Q

if atmospheric pressure = 760 mmHg what is pp N2 an pp O2

A 
N2 = 760 x 0.79 = 600 mmHg
O2 = 760 x 0.21 = 16 mmHg
103
Q

what is PAO2 (ppO2 in alveolar air)

A

air in resp tract saturated with water

104
Q

what is the water vapour pressure in the resp tract

A

47 mmHg (of total pressure)

105
Q

calculate the pressure of inspired air

A

atmospheric pressure - water vapour pressure

760 - 47 = 713 mmHg

106
Q

calculate the ppO2 inspired air

A

0.21 x 713 = 150 mmHg

107
Q

what is the alveolar gas equation

A 
PAO2 = piO2 - [PaCO2/0.8]
0.8 = resp exchange ratio
108
Q

why is there a small gradient between PAO2 (alveolar PO2) and PaO2 (arterial PO2)

A

ventilation-perfusion is not a perfect match

109
Q

if there is a big difference between alveolar PO2 and arterial PO2 what does this suggest

A

problems with gas exchange

right to left shunt in heart

110
Q

why are alveoli suited to gas exchange

A

large SA
thin membrane
single layered walls
flattened type 1 alveolar. cell

111
Q

factors that make the lungs suitable for gas exchange

A 
large SA
thin membrane
alveoli
repeated airway divisions
extensive capillary network 
narrow interstitial space
pulmonary circulation receives entire CO
112
Q

7 noinrespiratory functions for the respiratory system

A

Route for water loss & heat elimination
Enhances venous return
maintain acid-base balance
speech, singing
Defence against pathogens
Removes, modifies, activates/inactivates materials passing though pulmonary circulation
Nose = smell

113
Q

define henry’s law

A

Amount of gas dissolved and volume of liquid eg. Blood at constant temp is proportional to the partial pressure of the gas in equilibrium with the liquid

114
Q

according to henrys law what happens as pp increases

A

increased amount of gas dissolved in the liquid phase and proportionally increase gas concentration in gaseous phase

115
Q

what is pp gas in solution

A

gas mixture in equilibrium

116
Q

2 ways oxygen can be transported in the body

A

as dissolved oxygen

transported by haemoglobin

117
Q

what is the amount of oxygen transported in the blood proportional to

A

oxygens partial pressure

118
Q

at PO2 13.3kPa how much O2 is dissolved in blood

A

3 ml per L
not enough oxygen transported this way
O2 dissolved = 1.5%

119
Q

at resting, how much oxygen is dissolved in the blood

A 
CO = 5L/min
3x5 = 15ml/min taken into tissues
120
Q

what is resting O2 body cell consumption

A

250 ml/min

121
Q

during strenuous exercise how much oxygen is dissolved in the blood

A

CO = 30 L/min
3x30 = 90 ml/min into tissues
O2 consumption increases 25 fold

122
Q

how is most oxygen transported in the blood

A

attached to Hb

123
Q

what is O2 conc in arterial blood

A

200 ml/L

124
Q

wha tis normal arterial PO2

A

13.3 kPa

125
Q

what Is normal Hb conc in blood

A

150 g/L

126
Q

what percent of Oxygen is usually bound to Hb in healthy individuals

A

98.5%

>95%

127
Q

describe Hb structure and function

A

reversibly binds O2

4 haem groups - a & b chains and Fe

128
Q

what is co-operativity

A

the binding of one oxygen molecule to a haem group increases the affinity of the remaining subunits for oxygen
produces a sigmoid curve

129
Q

what is the primary factor determining % Hb saturation

A

PO2

as pO2 increases saturation inreases

130
Q

why does the sigmoid curve of Hb saturation flatten out, advantage of this

A

all the sites are occupied

advantage: moderate fall in PO2 doesn’t affect O2 loading

131
Q

advantage of a sigmoid curve steep part for Hb saturation

A

tissues get lots of O2 for small drop in capillary PO2

132
Q

No matter the Hb conc will always reach 100% saturation of the haemoglobin present as it is dependant on pO2
More haemoglobin = more O2 carried
True or False

A

True

133
Q

what is O2 delivery to tissues dependant on

A

O2 in arterial blood

CO

134
Q

Oxygen delivery index equation

A

DO2l = CaO2 x Cl
CaO2 = oxygen content of arterial blood
Cl = cardiac index
(2.4 -4.2 L/min/metre)

135
Q

what is the oxygen content of arterial blood determined by

A

Hb concentration

Hb saturation with O2

136
Q

equation for oxygen content of arterial blood

A 
CaO2 = 1.34 x [Hb] x SaO2
SaO2 = % Hb saturated with O2
137
Q

how much O2 does 1g Hb Carry when fully saturated

A

1.34 ml

138
Q

what is oxygen delivery to tissues impaired by

A

respiratory disease - affects pO2
heart failure - not enough blood carrying O2 pumped to tissues, decreased CO
Anaemia - not sufficient Hb
Decreased pp inspired O2

139
Q

what happens if pO2 becomes low

A

less binding to Hb

decreased arterial pO2 and decreased Hb saturation

140
Q

Bohr effect at tissues

A

Hb saturation curve shifts to the right

decreases affinity so O2 unloading at tissues

141
Q

how is O2 release at tissues increased

A

Increased PCO2
Increased H+
Increase temp
Increased 2,3 Biphosphoglycerate

142
Q

how does foetal haemoglobin differ from adult haemoglobin

A

2a + 2 y subunits (HbA has 2a + 2b)
interacts less with 2,3-biglycerate
higher O2 affinity curve shifted to left of HbA

143
Q

why is it advantageous HbF has greater affinity for O2 than HbA

A

Allows O2 delivery to foetus across placental if mothers PO2 lowered

144
Q

where is myoglobin in body

A

skeletal & cardiac muscle cells

145
Q

how does myoglobin differ from haemoglobin

A

1:1 binding
1 haem group so no co-operativity
hyperbolic cuve

146
Q

myoglobin releases O2 at very high/low pO2

A

low

147
Q

why is myoglobin used

A

short term O2 storage - anaerobic conditions

148
Q

what does myoglobin in blood suggest

A

muscle damage

149
Q

how is CO2 transported in the body

A

10% in solution (henrys law, 20 x more soluble than O2)
60% as Bicarbonate
30% as carbamino compounds

150
Q

how is CO2 transported as bicarbonate

A

In red blood cells

CO2 + H20 reversibly converted to H2CO3 which is reversibly converted to H+ & HCO3-

151
Q

what enzyme catalyses conversion of CO2 and H2O to H2CO3

A

carbonic anhydrase

152
Q

what are the H ions produced alongside bicarbonate used for

A

combine to form haemoglobin

153
Q

how is CO2 transported as carbamino compounds

A

CO2 & terminal amine group in blood proteins

carbamino-haemoglobin

154
Q

benefit of using carbamino-haemoglobin to transport CO2

A

rapid even without enzyme

155
Q

if Hb is reduced binds more/less CO2 than HbO2

A

more CO2 than HbO2

156
Q

what is the Haldane effect

A

Removing O2 from Hb increases the ability of Hb to pick-up CO2 and CO2 generated H+

157
Q

Haldane + Bohr effect facilitate:

A

O2 liberation
CO2 uptake & CO2 generated H+ at tissues
Curve in tissues shifted to the right and the amount of O2 given up is calculated by the difference in curves of arterial and tissue conditions

158
Q

in the Haldane effect what O2 shifts CO2 dissociation curve to the left/right

A

right

159
Q

what is PO2 venous blood

A

5.3

160
Q

at the lungs when Hb picks up O2 what happens to CO2 and H+ binding

A

binding weakens

161
Q

how is respiration controlled

A

neural control

Chemical control

162
Q

where is the centre of control for respiration

A

Medulla

normal ventilation above - Pons, ventilation ceases below

163
Q

what is the neural network that creates the rhythm of breathing located in the medulla

A

Pre-botzinger complex

164
Q

where is the pre-botzinger complex located

A

upper end of medullary resp tract

165
Q

how does the pre-botzinger complex create a breathing rhythm

A

excites dorsal neutrons (inspiratory) which fire in bursts causing contraction of inspiratory muscles when firing stops passive expiration

166
Q

What neurones are responsible for hyerventilation (active expiration) by exciting internal intercostals

A

increased dorsal firing excites VENTRAL neurones

contraction of abdomen, forceful expiration

167
Q

role of the Pons in breathing

A

modifies rhythm

168
Q

what is located in the pons and what is its role

A

Pneumotaxic centre: terminates inspiration

169
Q

how is the pneumotaxic centre stimulated

A

when dorsal resp neurones fire, inhibiting inspiration

170
Q

What does do no pneumotaxic centre result in

A

Apneusis: prolonged breathing inspiratory gaps brief expiration

171
Q

role of the apneustic centre

A

impulses from these neurones excite inspiratory are of medulla, prolonged inspiration

172
Q

4 centres in the medulla

A

Pneumotaxic centre
Dorsal neurones (inspiratory)
Apneustic centre
Ventral resp

173
Q

what higher brain centres influence resp centres

A

limbic system
cerebral cortex
hypothalamus

174
Q

what stimuli influences respiratory centres

A 
stretch receptors in bronchi
J receptors
Joint receptors
Baroreceptors
Central + Peripheral chemoreceptors
175
Q

what is the herring-breur reflex

A

protects agains hyperinflation (during exercise)
Discharge inhibits inspiration, activated at large tidal volumes (1L)
new born babies

176
Q

what are J receptors stimulated by

A

pulmonary capillary congestion
pulmonary oedema (left heart failure)
pulmonary emboli

177
Q

what do J receptors cause

A

low shallow breathing

178
Q

what effect do baroreceptors have on resp

A

increased ventilatory rate in response to decreased BP

179
Q

what effect does the joint receptor reflex have on respiratory

A

during exercise, impulses from moving limbs increases breathing + ventilation

180
Q

where is the cough reflex initiated

A

medulla

181
Q

what happens during the cough reflex

A

short breath intake
larynx closure
abdominal muscles contract (increase alveolar pressure)
larynx opens and air expulsion at high speed

182
Q

5 factors that increase ventilation In exercise

A 
Reflexes from body movement
Adrenaline release
Cerebral cortex impulses
Increased temp
Later: CO2 &amp; H in active muscles
183
Q

what do peripheral chemoreceptors detect

A

sense O2 + CO2 tension

Sense [H+] in blood

184
Q

where are central chemoreceptors located

A

medulla surface

185
Q

role of central chemoreceptors

A

Sense [H+] of cerebrospinal fluid (CSF)

CSF less proteins than blood so less buffered

186
Q

what is CSF separated from the blood by

A

blood brain barrier

187
Q

what gasses is the bbb permeable and impermeable to

A

permeable to CO2

impermeable to H & HCO3

188
Q

What is hypercapnia

A

PCO2 responsive ventilation

CO3 generates H through central chemoreceptors

189
Q

what is hypoxic drive stimulated by

A

peripheral chemoreceptors

190
Q

what happens when hypoxia is severe

A

neurones depressed

191
Q

how is hypoxic drive stimulated

A

when arterial PO2 falls to low level >8 kPa

192
Q

what patients is chronic CO2 retention present

A

COPD

193
Q

when can hypoxia occur

A

at high altitudes as there is decreased PiO2

194
Q

what is the acute response to high altitudes

A

hyperventilation and increased CO

195
Q

what adaptations occur to combat hypoxia

A

increased RBC (polycythaemia)
increased 2,3 BPG in RBCS - O2 offloading easier
Increased capillaries: more diffusion
increased mitochondria
kindres conserve acid (decrease arterial pH)

RESPIRATORY (12 decks)

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