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physiology Flashcards

1
Q

what does internal respiration refer to?

A

the intracellular mechanisms which consume O2 and produce CO2

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2
Q

what does external respiration refer to?

A

to the sequence of events that lead to the exchange of 02 and CO2 between the external environment and the cells of the body

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3
Q

four steps involved in external respiration

A

ventilation, exchange of O2 and CO2 between air in alveoli and blood coming into lungs, transport of O2 and CO2 in blood between the lungs and tissues, exchange of O2 and CO2 between the blood and tissues

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4
Q

four body systems involved in external respiration

A

the respiratory system, the cardiovascular system, the haematology system, the nervous system

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5
Q

Ventilation definition

A

the mechanical process of moving air between the atmosphere and alveolar sacs

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6
Q

are the lung movements active or passive

A

passive

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7
Q

what muscles are involved in the movement of the lungs?

A

respiratory muscles

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8
Q

what is inspiration

A

an active process brought about by contraction of inspiratory muscles

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9
Q

what is normal resting expiration

A

a passive process brought about by relaxation of inspiration muscles

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10
Q

what are the major functions of nasal breathing

A

to heat and moisten the air

and to remove particulate matter

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11
Q

what does cilia in nasal epithelium do?

A

move mucus back to the oropharynx to be swallowed

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12
Q

lung ventilation can be considered in two parts, what are they?

A

the mechanical process of inspiration and expiration and the control of respiration to a level appropriate for metabolic needs

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13
Q

how does lung volume affect the intrapleural pressure?

A

the higher the lung volume, the more the lung stretches, creating more negative intrapleural pressure

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14
Q

what are the responses by the lungs governed by

A

opposing forces

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15
Q

what are the forces that cause lungs to be hindered/ impeded?

A

elastic resistance (of lungs and chest wall) and non elastic resistance (airway resistance)

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16
Q

How do lungs adhere to the chest wall and follow its movement?

A

due to transmural pressure gradient and the intrapleural fluid cohesiveness

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17
Q

what is the transmural pressure gradient

A

the sub atmospheric intrapleural pressure (intrathoracic): creates a transmural pressure gradient across the lung wall and across the chest wall

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18
Q

what is intrapleural fluid cohesiveness?

A

the water molecules in the intrapleural fluid are attached to each other and resist being pulled apart. Hence the pleural membranes tend to stick together.

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19
Q

what are the three pressures that are important in resp?

A

atmospheric pressure which is the pressure in the atmosphere, intra alveolar (intrpulmonary) pressure which is the pressure within the lung alveoli and intrapleural pressure (intrathoracic) which is the pressure exerted outside the lungs within the pleural cavity and is usually less than the atmospheric pressure.

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20
Q

usual atmospheric pressure

A

760mmHg

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21
Q

usual intra alveolar pressure

A

760mmHg

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22
Q

usual intra pleural pressure

A

756mmHg

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23
Q

what will occur to the lungs if there’s no transmural gradient

A

they will collapse

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24
Q

where is there air when there’s a pneumothorax

A

in the pleural space

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25
Q

what can cause a pneumothorax

A

it can be traumatic, iatrogenic or spontaneous

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26
Q

how does a pneumothorax occur

A

air enters the pleural space, abolishing the transmural pressure gradient due to the increase in the intrathoracic pressure, leading to lung collapse

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27
Q

symptoms of pneumothorax

A

shortness of breath and chest pain

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28
Q

physical signs of a pneumothorax

A

hyper resonate percussion note and decreased/absent breath sounds

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29
Q

what’s boyles law

A

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

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30
Q

what occurs to the volume of the gas as the pressure exerted by the gas decreases

A

volume of gas increases

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31
Q

why does the intra alveolar pressure need to be less than the atmospheric pressure?

A

because air flows down a pressure gradient from high pressure to low pressure.

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32
Q

how does the intra alveolar pressure drop?

A

before inspiration the pressures are the same but when inspiring, the inspiration muscles contract causing the thorax and lungs to expand, increasing the volume of the gas in the lungs and hence decreasing the intra alveolar pressure

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33
Q

how does passive inspiration occur?

A

the lungs recoil, decreasing the size of lungs and hence decreasing the volume of gas in the lungs, this increases the intra alveolar pressure to 761mmHg and causes the gas to leave the lungs down its pressure gradient until the intra alveolar pressure becomes equal with the atmospheric pressure

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34
Q

what causes lungs to recoil during expiration?

A

elastic recoil of the lungs and alveolar surface tension

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35
Q

what is alveolar surface tension

A

its the attraction between water molecules at the liquid air interface, in the alveoli this produces a force which resists the stretching of the lungs

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36
Q

what would occur if the alveoli were only lined with water?

A

the surface tension would be too high, causing the alveoli to collapse

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37
Q

what do type II alveoli secrete

A

pulmonary surfactant

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38
Q

what is pulmonary surfactant made up of

A

a complex mixture of lipids and proteins

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39
Q

what does pulmonary surfactant do

A

it lowers the surface tension by interpreting between the water molecules lining the alveoli, smaller alveoli are more likely to collapse so pulmonary surfactants lower the pressure of these more

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40
Q

what law proves the smaller alveoli have a higher tendency to collapse

A

law of LaPlace

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41
Q

what can cause respiratory distress syndrome in premature babies?

A

developing fatal lungs are unable to produce surfactant until late in pregnancy and so premature babies may not have enough pulmonary surfactant causing very high surface tension and lungs can collapse.

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42
Q

what keeps alveoli open?

A

surfactant, alveolar interdependence, transmural pressure gradient

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43
Q

what’s alveolar interdependence

A

once an alveolus begins to collapse it stretches in its surrounding alveoli, these then recoil causing the collapsing alveolus to open

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44
Q

what’s promotes alveolar collapse

A

surface tension and elastic recoil of chest walls and lungs

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45
Q

major inspiratory muscles

A

diaphragm and external intercostal muscles

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46
Q

accessory inspiratory muscles

A

pectoral, scalenus and sternocleidomastoid

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47
Q

muscles pf active expiration

A

internal intercostal muscles and abdominal muscles

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48
Q

what is the tidal volume and its average value

A

is the volume of air entering or leaving lungs during a single breath, it’s on average 0.5L

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49
Q

what is the inspiratory reserve volume and its average value

A

this is the volume of air that can be maximally inspired over and above the typical resting tidal volume, it’s on average 3L

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50
Q

what is the expiratory reserve volume and its average value

A

this is the extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume, it’s average value is 1L

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51
Q

what is the residual volume and what is it’s average value

A

the residual volume is the volume of air remaining in the lungs even after a maximal expiration, the average value for this is 1.2L

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52
Q

what is the inspiratory lung capacity and its average value

A

the maximum volume of air that can inspired at the end of a normal quiet inspiration IC= IRV + TV, its average value is 3.5L

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53
Q

What is the functional residual capacity and its average value

A

volume of air in lungs at the end of normal passive expiration FRC= ERV + RV, its average value is 2.2L

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54
Q

What is the vital capacity and its average value?

A

the maximum volume of air that can be moved out during a single breath following a maximal inspiration VC= IRV + TV + ERV, average value is 4.5L

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55
Q

what is the total lung capacity and its average value?

A

this is the total volume of air the lungs can hold TLC= VC + RV, average value is 5.7L

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56
Q

what cannot be ,measured using spirometry

A

residual volume and hence can’t measure total lung capacity or functional residual capacity.

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57
Q

FVC definition

A

maximum volume that can be forcibly expired from the lungs following maximum inspiration

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58
Q

FEV1

A

the volume of air that can be expired during the first second in an FVC determination

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59
Q

FEV1/FVC

A

the proportion of FVC that can be expired in the first second

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60
Q

what value is FEV1/FVC x 100 normally

A

> 75%

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61
Q

what is the FEV1/FVC% for someone with asthma or COPD

A

<75%

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62
Q

how can spirometry help tell difference between obstructive or restrictive lung diseases

A

because obstructive such as asthma are reversible and so its FEV1/FVC% should go back to normal after taking an inhaler whereas restrictive such as COPD will not, also the FVC of COPD is lowered whereas it does not lower for asthma

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63
Q

what is a primary determination of airway resistance

A

the smaller the airway, t he greater the resistance and hence greater the pressure

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64
Q

what causes bronchodilation

A

parasympathetic stimulation

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65
Q

what makes active expiration more difficult for patients with airway obstruction

A

dynamic airway compression

66
Q

why does dynamic airway obstruction make active expiration harder for patients with an obstructed airway

A

because if there’s an obstruction the driving pressure between the alveolar and the airway is lost over the obstructive segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration.

67
Q

what can make active expiration even harder for patients with an obstructed airway on top of dynamic airway obstruction

A

if the patient has decreased elastic recoil in the lungs

68
Q

what does the peak flow meter measure

A

the peak flow rate which allows us to assess airway function

69
Q

what diseases is peak flow meter useful for

A

obstructive lung disease (asthma and COPD)

70
Q

how does a patient use a peak flow meter

A

they take a short sharp breath into it and the three best attempts are taken

71
Q

what is compliance

A

the measure of the effort that has gone into stretching or distending the lungs

72
Q

what is lung compliance ?

A

the change in lung volume per unit change in transmural pressure gradient across the lung wall (i.e. the difference between intra alveolar sonf intrapleural pressure)

73
Q

what does less compliance mean for the lungs?

A

more work is required to produce a degree of inflation

74
Q

what can cause decreased pulmonary compliance

A

pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia or absence of surfactant

75
Q

what does a decrease in pulmonary compliance cause?

A

it means a greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer). This causes shortness of breath especially on exertion

76
Q

how does a decrease in pulmonary compliance affect a spirometry

A

it may cause a restrictive pattern of lung volumes

77
Q

when does compliance abnormally increase

A

if elastic recoil of the lungs is lost (if a patient has an emphysema)

78
Q

what does abnormally increased pulmonary compliance do

A

it means the patient has to work harder to get air out of the lungs- hyperinflation of the lungs

79
Q

what is work of breathing

A

a reflection of energy required to overcome the impeding elements of the resp system

80
Q

examples of when work of breathing is increased

A

during decreased pulmonary compliance, increased airway resistance, decreased elastic recoil and when there’s a need for increased ventilation

81
Q

what’s dead space

A

the air that remains in the airway and is not available for gas exchange

82
Q

calculation for pulmonary ventilation

A

PV= tidal volume x respiration rate

83
Q

calculation for alveolar ventilation

A

AV = (tidal volume- dead space) x respiration rate

84
Q

pulmonary ventilation definition

A

volume of air breathed in and out per min

85
Q

alveolar ventilation definition

A

volume of air exchanged between the atmosphere and alveoli per minute

86
Q

how do you increase pulmonary ventilation

A

increase both tidal volume (depth of breathing) and the resp rate

87
Q

how do you increase alveolar ventilation

A

due to dead space its more advantageous to increase the depth of breathing (tidal volume)

88
Q

what does the transfer of gases between the body depend on?

A

ventilation and perfusion

89
Q

what is perfusion

A

the rate at which blood is passing through the lungs

90
Q

are blood flow and perfusion constant throughout the lung

A

no they vary throughout the bottom to the top of the lung

91
Q

what does the variation of blood flow and perfusion throughout the lung result in

A

that the average arterial and alveolar pressures of O2 are not exactly the same, normally this effect is not significant but it can be in disease.

92
Q

what is alveolar dead space

A

alveoli which are ventilated but not adequately perfused with blood

93
Q

what is alveolar dead space like for healthy people

A

it’s small and of little importance

94
Q

how could you calculate the physiological dead space

A

the anatomical dead space + the alveolar dead space

95
Q

how can alveolar dead space increase

A

in disease

96
Q

what does accumulation of CO2 due to increased perfusion cause at the alveoli?

A

this decreases airway resistance, increasing airflow

97
Q

what does increase in alveolar O2 due to increased ventilation cause?

A

this causes pulmonary vasodilation which increases blood flow to match larger airflow

98
Q

what occurs if perfusion is greater than ventilation?

A

CO2 increases and O2 decreases, dilation of local airway due to CO2 increase and construction of local blood vessels due to O2 decrease, the airflow increases and blood flow decreases to try and even out

99
Q

what occurs if ventilation is greater than perfusion ?

A

O2 increases, dilating the local blood vessels, increasing blood flow and CO2 decreases, constricting local airways, decreasing airflow

100
Q

what occurs to pulmonary arterioles as O2 is increased/ decreased

A

O2 increased- vasodilation and decreased O2- vasoconstriction

101
Q

what occurs to systemic arterioles as O2 is increased/decreased

A

O2 decreased- vasodilation and )2 increased- vasoconstriction

102
Q

what is partial pressure

A

the partial pressure of a gas determines the pressure gradient for that gas

103
Q

what is the partial pressure of gas in a mixture of gases that don’t react with each other?

A

the pressure that gas (1) would exert if it occupied the total volume for the mixture in absence of other components

104
Q

total pressure exerted by all the gases calculation

A

total pressure= P1 + P2 + P3.. + Pn

105
Q

what is the alveolar gas equation?

A

PaO2= PiO2- [PaCO2/0.8]

106
Q

how would you calculate PiO2 in the alveolar air

A

pressure inspired= atmospheric pressure- water vapour pressure , then PiO2= pressure inspired x percent of O2

107
Q

why is the partial pressure gradient of CO2 much smaller than the partial pressure of O2?

A

CO2 is more soluble in membranes than O2, so has a larger Diffusion Coefficient

108
Q

what would a large gradient between PAO2 and PaO2 suggest?

A

this would indicate problems with gas exchange or problems with the exchange of blood from left to right side of the heart.

109
Q

Fick’s law

A

the amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness

110
Q

what increases the surface area in lungs

A

the alveoli

111
Q

4 factors that influence the rate of gas transfer across the alveolar membrane

A

partial pressure gradient of O2 and CO2, diffusion coefficient, surface area of alveolar membrane and thickness of alveoli membrane

112
Q

what occurs to rate of transfer as partial pressure increases

A

rate of transfer increases

113
Q

what can decrease surface area of alveolar membrane

A

emphysema, lung collapse and pneumonectomy

114
Q

what increases thickness of alveolar membrane

A

same stuff that decreases lung compliance (pulmonary oedema, pulmonary fibrosis and pneumonia)

115
Q

what is Henry’s Law?

A

the amount of gas dissolved in a given type and volume of liquid (blood) at a constant temp is proportional to the partial pressure of the gas in equilibrium with the liquid

116
Q

O2 is present in the blood in what forms?

A

bound to haemoglobin and physically dissolved

117
Q

how is most O2 transported

A

it’s bound to haemoglobin

118
Q

percent of O2 bound to haemoglobin compared to carried in dissolved form

A

bound to haemoglobin- 98.5% whereas carted in dissolved form- 1.5%

119
Q

how many harm groups does haemoglobin contain

A

4

120
Q

when is haemoglobin considered fully saturated

A

when all the haemoglobin present is carrying its maximum O2 load

121
Q

what is a primary factor that determines percent saturation of haemoglobin

A

PO2

122
Q

what occurs to % haemoglobin saturation as partial pressure increases?

A

the % haemoglobin sat increases as more haemoglobin present is carrying O2.

123
Q

how much O2 is taken to tissues under resting conditions

A

15ml/min

124
Q

how much O2 is taken to tissues under strenuous exercise

A

90ml/min

125
Q

what is resting O2 consumption of our body cells

A

250ml/min

126
Q

oxygen delivery index calculation

A

DO2I= CaO2 (oxygen content of arterial blood) x Cl (cardiac index)

127
Q

what determines the O2 content of arterial blood?

A

Hb concentration and saturation of Hb with O2 ( and saturation depends on partial pressure)

128
Q

how much )2 does a gram of Hb carry when fully saturated

A

1.34

129
Q

what does the partial pressure of inspired oxygen depend on

A

total pressure (atmospheric pressure) and proportion of oxygen in gas mixture (about 21% in atmosphere)

130
Q

what can oxygen delivery to tissues be impaired by

A

decreased partial pressure of inspired oxygen and respiratory disease as these can decrease arterial PO2 and hence decrease Hb saturation with O2 and O2 content of the blood.

131
Q

how may anaemia affect oxygen delivery to tissues

A

it will impair it as it decreases Hb concentration and so decreases O2 content of the blood

132
Q

how does heart failure affect oxygen delivery to tissue

A

heart failure impairs it as it decreases cardiac output

133
Q

what shape does Hb binding cause on a graph

A

sigmoid

134
Q

why when one O2 binds to Hb does affinity of Hb increase for another O2

A

due to cooperativity

135
Q

what does the flat upper portion of the Hb sigmoid graph mean

A

it means the MODERATE FALL IN ALVEOLAR P02 WILL NOT HAVE MUCH AFFECT OXYGEN LOADING

136
Q

what does the steep lower part of the Hb sigmoid graph mean

A

it means that the peripheral tissues get a lot of oxygen for a small drop om capillary PO2

137
Q

what can shift the Hb saturation curve to the right, increasing release of O2 at tissues?

A

increase in PCO2, increase in [H+], increase in temperature, increase in 2,3- niphosphoglycerate

138
Q

what does 2,3-biphosphoglycerate do

A

it decreases affinity of Hb to oxygen

139
Q

why does HbF have a higher affinity for oxygen than Hb

A

because it interacts less with 2,3- biphopsphoglycerate

140
Q

how does HbF differ in structure from Hb

A

HbF has 2 alpha subunits and 2 gama subunits while Hb has beta subunits

141
Q

what does the HbF dissociation curve look like compared to the Hb dissociation curve

A

the HbF dissociation curve lies more to the left

142
Q

where is myoglobin found

A

in skeletal and cardiac muscles

143
Q

how many haem groups per myoglobin

A

1 haem group per myoglobin

144
Q

why is the myoglobin dissociation curve hyperbolic

A

because there’s no cooperativity binding of O2

145
Q

when does myoglobin release O2

A

at very low PO2

146
Q

what does myoglobin provide

A

a short-term storage of O2 for anaerobic conditions

147
Q

what does the presence of myoglobin in the blood indicate

A

muscle damage

148
Q

in what ways is CO2 transported in blood and what % of CO2 is transported in each way

A

solution 10%, bicarbonate 60%, carbonic compounds 30%

149
Q

how does henrys law apply to CO2

A

the amount of CO2 dissolved in blood is proportional to its partial pressure

150
Q

how much more soluble is CO2 in blood than O2

A

roughly 20 times

151
Q

how is bicarbonate formed in red blood cells

A

CO2 + H2O H2CO3H+ + HCO3

152
Q

how are carbamino compounds formed

A

by combination of CO2 with terminal amine groups in blood proteins

153
Q

what can reduced Hb bind more to than HbO2

A

CO2

154
Q

do carbon compounds require enzymes

A

no, they are rapid even without

155
Q

what’s the Haldane effect

A

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

156
Q

what happens when the Boher effect and Haldane effect work together

A

they facilitate O2 liberation and uptake of CO2 and CO2 generates H+ at tissues

157
Q

what occurs to Hb at the lungs

A

Hb pick up O2, weakening the ability to bind CO2 and H+

158
Q

where do oxygen and CO2 bind to on the Hb molecule

A

O2 binds to the haem part, CO2 binds to the globing part

159
Q

what part of the brain generated rhythm for breathing

A

the medulla

160
Q

what network of neutrons generate rhythm

A

a network of neurons called the pre-botzinger complex

161
Q

where are is the pre-botzinger complex located

A

near the upper end of the medullary respiratory centre

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