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Physiology Flashcards

1
Q

What is external respiration?

A

the sequence of events that leads to the exchange of oxygen and carbon dioxide between the external environment and the cells of the body.

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2
Q

Name the four steps of external respiration

A

Ventilation, gas exchange between alveoli and blood, gas transport in the blood, gas exchange at tissue level

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3
Q

State Boyle’s law

A

At any constant temperature the pressure exerted by a gas varies inversely with the volume of the gas. As the volume of a gas increases, the pressure exerted by the gas decreases.

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4
Q

What are the two forces that hold the thoracic wall and the lungs in close opposition?

A
  1. intrapleural fluid cohesiveness: the water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. Hence the pleural membranes tend to stick together.
  2. negative intrapleural pressure: the sub-atmospheric intrapleural pressure creates a transmural pressure gradient across the lung wall and across the chest wall. So the lungs are forced to expand outwards while the chest is forced to squeeze inwards.
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5
Q

What are the typical values of: atmospheric pressure, intra alveolar pressure and intrapleural pressure?

A

760, 760, 755

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6
Q

What is a pneumothorax?

A

Air in the pleural space

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7
Q

What causes lungs to recoil during expiration?

A

Elastic connective tissue and alveolar surface tension

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8
Q

Explain the law of LaPlace in relation to small alveoli

A

the smaller alveoli have a higher tendency to collapse

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9
Q

What is pulmonary surfactant?

A

A complex mixture of lipids and proteins secreted by type II alveoli. It lowers alveolar surface tension.

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10
Q

What is alveolar interdependence?

A

if an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting expanding forces in the collapsing alveolus to open it.

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11
Q

Name the accessory muscles of inspiration, the major muscles and the muscles of active expiration.

A

Scalenus and sternocleidomasteod, extenal intercostal muscles and diaphragm, abdominal muscles

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12
Q

Tidal volume volume

A

500ml

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13
Q

Inspiratory reserve volume volume

A

3000ml

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14
Q

Inspiratory capacity volume

A

3500ml

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15
Q

expiratory reserve volume volume

A

1000ml

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16
Q

residual volume volume

A

1200ml

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17
Q

functional residual capacity volume

A

2200ml

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18
Q

vital capacity volume

A

4500ml

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19
Q

total lung capacity volume

A

5700ml

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20
Q

What is the tidal volume?

A

The volume of air entering and leaving the lungs during a single breath

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21
Q

What is the inspiratory reserve volume?

A

The extra volume of air that can be maximally inspired over and above the typical resting tidal volume

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22
Q

What is the inspiratory capacity?

A

The maximum volume of air that can be inspired at the end of a normal quiet expiration. IC = TV + IRV

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23
Q

What is the expiratory reserve volume?

A

The extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume.

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24
Q

What is the residual volume?

A

The minimum volume of air remaining in the lungs even after maximal expiration.

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25
Q

What is functional residual capacity?

A

The volume of air in the lungs at the end of normal passive expiration (FRC = ERV + RV)

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26
Q

What is the vital capacity?

A

The maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV)

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27
Q

What is total lung capacity?

A

The maximum volume of air that the lungs can hold (TLC = VC + RV)

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28
Q

What is forced expiratory volume in one second (FEV1) ?

A

Th volume of air that can be expired during the first second of expiration in an FVC determination. A ration with a percentage above 75% is normal.

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29
Q

What does parasympathetic stimulation do to the bronchioles?

A

Causes bronchoconstriction

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30
Q

What does sympathetic stimulation do to the bronchioles?

A

Causes bronchodilatation

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31
Q

What is pulmonary compliance?

A

The measure of effort that has to go into stretching or distnding the lungs

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32
Q

Name five factors that decrease pulmonary compliance

A

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

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33
Q

In what condition does increased compliance occur?

A

emphysema

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34
Q

What is anatomical dead space?

A

Inspired air that remains in the airways and is not available for gas exchange (150ml)

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35
Q

What is pulmonary ventilation?

A

The volume of air breathed in and out per minute. TV + RR = 0.5 + 12 = 6 L/min

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36
Q

Why is alveolar ventilation less than pulmonary ventilation?

A

Because of the presence of anatomical dead space

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37
Q

What is alveolar ventilation?

A

The volume of air exchanged between the atmosphere and alveoli per minute. It represents the new air available for gas exchange with blood. (TV - dead space) x RR = (0.5 - 0.15) x 12 = 4.2 L/min

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38
Q

What does decreased oxygen do to pulmonary arterioles?

A

Vasoconstriction

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39
Q

What does increased oxygen do to pulmonary arterioles?

A

Vasodilatation

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40
Q

What does decreased oxygen do to systemic arterioles?

A

Vasodilatation

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41
Q

What does increased oxygen do to systemic arterioles?

A

Vasoconstriction

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42
Q

State Dalton’s law

A

the total pressure exerted by a gaseous mixture depends on the sum of the partisl pressures of each individual component in the gas mixture

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43
Q

How much does watere vapour pressure contribute to the total pressure in the lungs?

A

47 mmHg

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44
Q

What is the pressure of inspired air and how was it worked out?

A

atmospheric pressure - water vapour pressure = 760 - 47 = 713 mm Hg

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45
Q

What is the partial pressure of oxygen?

A

150 mmHg

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46
Q

Across pulmonary capillaries: what is the partial pressure gradient of oxygen from alveoli to blood?

A

60 mmHg

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47
Q

Across the pulmonary capillaries: what is the partial pressure gradient of carbon dioxide from blood to alveoli?

A

6 mmHg

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48
Q

Across systemic capillaries: what is the partial pressure gradient of oxygen from blood to tissue cell?

A

greater than 60 mmHg

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49
Q

Across systemic capillaries what is the partial pressure gradient of carbon dioxide from tissue cell to blood ?

A

greater than 6 mmHg

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50
Q

Which is more soluble in membranes - CO2 or oxygen?

A

CO2

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51
Q

What is the solubility of gas in membranes known as?

A

The diffusion coefficient.

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52
Q

How much greater is the diffusion coefficient for C02 compared to oxygen?

A

20 times greater

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53
Q

What would a big gradient between PA02 and Pa02 indicate?

A

Problems with gas exchange in the lungs or a right to left shunt in the heart

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54
Q

How much of the cardiac output does the pulmonary circulation receive?

A

The entire cardiac output

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55
Q

What has a respiratory membrane?

A

Alveoli

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56
Q

What do the walls of alveoli consist of?

A

Single layer of flattened type I alveolar cells

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57
Q

What encricles each alveolus?

A

Pulmonary capillaries

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58
Q

Name 4 factors that influence the rate of gas exchange across alveolar membranes?

A
  1. Partial pressure gradients of O2 and CO2
  2. Surface area of alveolar membrane
  3. Thickness of blood/air barrier across membrane
  4. Diffusion coefficient (solubility of gas in membrane)
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59
Q

In relation to the partial pressure gradients of O2 and CO2: what happens when the partial pressure increases?

A

Rate of transfer of gas exchange across alveolar membranes increases

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60
Q

In relation to hte surface area of alveolar membranes: what occurs when the surface area increases?

A

Rate of transfer increases

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61
Q

What does the surface area of alveolar membranes increase during and why?

A

During exercise as more pulmonary capillaries open up when the cardiac output increases and the alveoli expand as breathing deepens

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62
Q

In relation to the thickness of blood/air barrier across membranes: what occurs as it thickens?

A

Rate of transfer decreases

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63
Q

What does thickness of blood/air barrier across membrane increase with?

A

Pathological conditions such as pulmonary oedma, pulmonary fibrosis and pneumonia

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64
Q

In relation to the diffusion coefficient (solubility of gas in membrane): what occurs as the diffusion coefficient decreases?

A

Rate of transfer increases

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65
Q

Where must oxygen that has been picked up by the blood be transported to?

A

Tissues for cellular use

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66
Q

Where must CO2 produced at the tissues be transported to?

A

The lungs for removal from the body

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67
Q

What is the PO2 in atmospheric air?

A

160

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68
Q

What is the PCO2 in atmospheric air?

A

0.03

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69
Q

What is the PO2 in alveoli?

A

100

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70
Q

What is the PCO2 in alveoli?

A

40

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71
Q

What is the PO2 in deoxygenated blood?

A

40

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72
Q

What is the PCO2 in deoxygenated blood?

A

46

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73
Q

What is the PO2 in oxygenated blood?

A

100

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74
Q

What is the PCO2 in oxygenated blood?

A

40

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75
Q

In the tissues what is the PO2?

A

<40

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76
Q

In the tissues what is the PCO2?

A

> 46

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77
Q

What law relates to the effect of partial pressure on gas solubility?

A

Henry’s law

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78
Q

What is Henry’s law?

A

The amount of a given gas dissolve in a given type and volume of liquid (e.g. blood)v at a constant temperature is: proportional to the partial pressure of the gas in equilibrium with the liquid.

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79
Q

If the partial pressure in the gas phase is increased, what happens to the concentration of the gas in the liquid phase?

A

It would increase proportionally

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80
Q

What is the oxygen amount dissolved in blood proportional to?

A

The partial pressure

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81
Q

How much oxygen is there per litre of blood at P02 of 13.3kPa?

A

3ml

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82
Q

Under resting conditions - what is cardiac output?

A

5L/min

83
Q

Under resting conditions how much oxygen per minute is taken to tissues as dissolved O2?

A

15ml/min

84
Q

What is the cardiac output during strenuous exercise?

A

30L/min

85
Q

During srenuous exercise much much oxygen per minute would be taken to tissues as dissolved oxygen?

A

90ml/min

86
Q

What is the resting oxygen consumption of our body cells?

A

About 250ml/min

87
Q

How much may oxygen consumption increase during strenuous exericese?

A

25 folds

88
Q

How is most oxygen in the blood transported?

A

Bound to haemoglobin

89
Q

What is the normal oxygen concentration in the arterial blood at a normal arterial PO2 of 13.3kPa?

A

20ml/100ml (200ml per litre)

90
Q

What is the normal haemoglobin concentration at a normal arterial PO2 of 13.3kPa?

A

15g/100ml

91
Q

What is the percentage of oxygen carried bound to haemoglobin?

A

98.5%

92
Q

What is the percentage of oxygen carried in the dissolved form?

A

1.5% (3ml per litre at a PO2 of 13.3kPa

93
Q

What two forms is oxygen present in the blood in?

A

Bound to haemoglobin or physically dissolved

94
Q

What kind of combination does haemoglobin form with oxygen?

A

Reversible

95
Q

How many haem groups does a Hb molcule contain?

A

4 haem groups

96
Q

When is haemoglobin considered fully saturated?

A

When all the Hb present is carrying its maximum oxygen load

97
Q

What is the primary factor which determines the percent saturation of haemoglobin with oxygen?

A

PO2

98
Q

What is the equation for the oxygen delivery index? (DO2I)

A

DO2I = CaO2 x Cl

99
Q

What is CaO2?

A

Oxygen content of arterial blood (ml/L)

100
Q

What is CI?

A

Cardiac index (L/min/metre)

101
Q

What does the cardiac index relate to?

A

The cardiac output to the body surface area (i.e. size of the individual)

102
Q

What is the normal range for CL?

A

2.4 - 4.2 L/min/metre

103
Q

What is the oxygen delivery to the tissues a function of?

A

Oxygen content of arterial blood and the cardiac output

104
Q

What is the equation for the oxygen content of arterial blood (CaO2)?

A

CaO2 = 1.34 x [Hb] x SaO2

105
Q

How much oxygen does 1 gram of Hb carry when fully saturated?

A

1.34ml

106
Q

In the oxygen content of arterial blood (CaO2) equation: what is [Hb] and SaO2?

A 
[Hb] = haemoglobin concentration (gram/L)
SaO2 = %Hb saturated with O2 (remember this is determined by PO2)
107
Q

What is the oxygen content of arterial blood determined by?

A

Haemoglobin concentration [Hb] and the saturation of Hb with O2

108
Q

What three things can impair oxygen delivery to the tissues?

A

Respiratory disease
Heart failure
Anaemia

109
Q

What does the binding of one oxygen to Hb increase?

A

The affinity of Hb for oxygen

110
Q

What happens to haemoglobin where all the sites are becoming occupied?

A

Flattens

111
Q

What is co-operativity in relation to oxygen binding to haemoglobin?

A

Binding of one oxygen to Hb increaeses the affinity of Hb for oxygen

112
Q

What are heme group, beta chains and alpha chains all a part of?

A

Haemoglobin

113
Q

On a graph where the y axis is %haemoglobin saturation, x axis is blood PO2 (kPa) and the right axis is O2 concentration ml/100ml: What does the flat upper portions of a sigmoid curve mean?

A

Means that moderate fall in alveolar PO2 will not much affect oxygen loading.

114
Q

On a graph where the y axis is %haemoglobin saturation, x axis is blood PO2 (kPa) and the right axis is O2 concentration ml/100ml: What does the steep lower part of the sigmoid curve mean?

A

That the peripheral tissues get a lot of oxygen for a small drop in capillary PO2

115
Q

What is the Bohr effect - on a graph with y axis as % Hb saturation and x axis of PO2?

A

A shift of the curve to the right: The Bohr effect

116
Q

What 4 things increase to give the Bohr effect?

A
  1. PCO2
  2. [H+]
  3. Temperature
  4. 2,3-Bisphosphoglycerate
117
Q

The Bohr effect is a shift of the curve to the right, what does this mean?

A

Increased release of oxygen by conditions at the tissues

118
Q

What type of tension has 100 PO2 and 13.3kP?

A

Arterial O2 tension

119
Q

What type of tension has PO2 of 40 and 5.3kP?

A

Tissue oxygen tension

120
Q

On a graph with O2 content as the y-axis and PO2 (mm Hg, kP) as the x-axis: which curve is more left and finishes higher - curve in arterial conditions or curve in tissue conditions?

A

Curve in arterial conditions

121
Q

Where is myoglobin present?

A

In skeletal and cardiac muscles

122
Q

How many haem groups per myoglobin molecule?

A

one

123
Q

In relation to myoglobin is htere any cooperative binding of oxygen?

A

No

124
Q

On a graph with % saturation of myoglobin on y-axis and PO2 mmHg on x-axis, what is the curve like?

A

Dissociation curve hyperbolic

125
Q

At what level of PO2 does myoglobin release oxygen?

A

At very low PO2

126
Q

On a graph with %saturation on y-axis and PO2 mmHg on x-axis: which curve is more left - dissociation curve for myoglobin (1:1 binding) or dissociation curve for haemoglobin?

A

Dissociation curve for myoglobin (1:1 binding)

127
Q

What does myoglobin provide a short term storage of oxygen for?

A

Anaerobic conditions

128
Q

What does the presence of myglobin the the blood indicate?

A

Muscle damage

129
Q

Describe the 3 means of CO2 transport in the blood (including %)

A
  1. Solution (10%)
  2. As Bicarbonate (60%)
  3. As Carbamino compounds (30%)
130
Q

What law is associated with CO2 transportation in solution?

A

Henry’s law

131
Q

How is most CO2 transported in the blood?

A

As bicarbonate

132
Q

What is the equation for Bicarbonate being formed in the blood?

A

CO2 + H20 = H2CO3 = H+ + HCO3

133
Q

Where does carbonic anhydrase occur?

A

In red blood cells

134
Q

How are carbamino compounds formed?

A

By the combination of CO2 with terminal amine groups in blood proteins

135
Q

What gives carbamino-haemoglobin?

A

Globin of haemoglobin and CO2

136
Q

Can reduced Hb bind more CO2 than HbO2?

A

Yes

137
Q

What is the haldane effect?

A

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

138
Q

What does the Haldane effect work in synchrony with?

A

The Boher effect

139
Q

What to effects work in synchrony to facilitate oxygen liberation and uptake of CO2 and CO2 generated H+ at tissues?

A

Boher effect and Haldane effect

140
Q

What is haemoglobin present in the red blood cells as?

A

Carbonic anhydrase

141
Q

What is the enzyme that caralyses the production of bicarbonate?

A

Carbonic anhydrase

142
Q

What does the H+ generated during the production of HCO3 bind to?

A

Hb

143
Q

How does bicarbonate move out of red blood cells and into the plasma?

A

By facilitated diffusion down its concentration gradient

144
Q

Name the 4 sections of the sagital brain stem from inner most to outer?

A
  1. Midpoint
  2. Pons
  3. Medulla oblongata
  4. Spinal cord
145
Q

What part of the brain stem is the major rythm generator?

A

Medulla

146
Q

What network of neurons generate the breathing rhythm?

A

Pre-Botzinger complex

147
Q

What kind of activity do Pre-Botzinger complex neurons display?

A

Pacemaker actiivty

148
Q

Where are the Pre-Botzinger complex neurons located?

A

Near the upper end of the medullary respiratory centre

149
Q

In the pons of the brainstem - what two centers are present?

A

Pneumotaxic center and apneustic center

150
Q

What respiratory group is the Pre-Botzinger complex above?

A

The ventral respiratory group

151
Q

Which respiratory group is posterior to the ventral respiratory group in the brain stem?

A

Dorsal respiratory group

152
Q

What two respiratory groups are in the medullary respiratory center?

A

Dorsal respiratory group

Ventral respiratory group

153
Q

What group of neurones in the brainstem give rise to inspiration?

A

The dorsal respiratory group neurones

154
Q

How do the dorsal respiratory group neurones fire?

A

In bursts

155
Q

What does firing of the dorsal respiratory group neurones lead to?

A

Contraction of inspiratory muscles - inspiration

156
Q

When firing of the dorsal respiratory group neurones stop - what happens?

A

Passive expiration

157
Q

During ‘active’ expiration during hyperventilation - what happens when there is increased firing of dorsal neruones?

A

They excite a second group called the ventral respiratory group neurones

158
Q

What do the ventral respiratory group neurones excite and what doesthis cause?

A

Excite internal intercostals, abdominals which leads to forceful expiration

159
Q

In normal quiet breathing, dp ventral neurones activate expiratory muscles?

A

No

160
Q

The rhythm generated in the medulla can be modified by what neurones?

A

In the pons

161
Q

What does stimulation of the pneumotaxic centre (PC) terminate?

A

Inspiration

162
Q

When is the pneumotaxic centre (PC) stimulated?

A

When the dorsal respiratory neurones fire

163
Q

When the PC is stimulated when dorsal respiratory neurones fire - what is inhibited?

A

Inspiration

164
Q

Without PC, breathing is prolonged inspiratory gasps with brief expiration - what is the name for this?

A

Apneusis

165
Q

What do impulses from the apneustic centre excite?

A

Inspiratory area of the medulla

166
Q

When the apneustic centre inpulses excite the respiratory area of the medulla what occurs?

A

Prolonged inspiration

167
Q

Where is the rythm generated and where can it be modified?

A

Generated in medulla and modified by inputs from pons

168
Q

Respiratory centres are influenced by stimuli received from what 7 receptors?

A
  1. Higher brain centres
  2. Stretch receptors
  3. Juxtapulmonary receptors
  4. Joint receptors
  5. Baroreceptors
  6. Central cehmoreceptors
  7. Peripheral chemoreceptors
169
Q

What are the 3 higher brain centres?

A

Cerebral cortex, limbic system, hypothalamus

170
Q

Where are stretch receptors located?

A

In the walls of the bronchi and bronchioles

171
Q

What does the inflation Hering-Breur reflex guard against?

A

Hyperinflation

172
Q

What 3 things stimulate the J receptors?

A

Pulmonary capillary congestion and pulmonary oedema, also pulmonary emboli

173
Q

What heart failure causes pulmonary oedema?

A

Left sided

174
Q

How are joint receptors stimulated?

A

Joint movement

175
Q

In relation to baroreceptors what causes increased ventilatory rate?

A

Decreased blood pressure

176
Q

Give 4 examples of involuntary modifications of breathing

A
  1. Pulmonary stretch receptors Hering-Breuer Reflex
  2. Joint receptors reflex in exercise
  3. Stimulation of respiratory centre by temperature, adrenaline, or impulses from cerebral cortex
  4. Cough refelx
177
Q

When are pulmonary stretch receptors activated and what do the afferent discharges inhibit?

A

Activated during inspiration, afferent discharge inhibits inspiration - Hering-Breur reflex

178
Q

At what level of tidal volumes are pulmonary stretch receptors activated?

A

At large&raquo_space; 1 litre tidal volumes

179
Q

What do impulses from moving limbs increase?

A

Breathing

180
Q

What 5 factors may increase ventilation during exercise?

A
  1. Reflexes originating from body movement
  2. Adrenaline release
  3. Impulses from the cerebral cortex
  4. Increase in body temperature
  5. Later: accumulation of CO2 and H+ generated by active muscles
181
Q

Where is the cough reflex control centre?

A

Centre in the medulla

182
Q

In relation to the cough reflex: what does afferent discharge stimulate?

A

Short intake of breath, followed by closeure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsin of air at a high speed

183
Q

What kind of feedback is chemical control of respiration an example pof?

A

Negative feedback

184
Q

In the chemical control of respiration: what are the controlled variables?

A

Blood gas tensions, especially carbon dioxide

185
Q

What do chemoreceptors sense the values of?

A

Gas tensions

186
Q

Where are the two peripheral chemoreceptors located?

A

Carotid bodies and aortic bodies

187
Q

What 3 things do the peripheral chemoreceptors sense?

A

Tension of oxygen, carbon dioxide and [H+] in the blood

188
Q

Where are the central chemoreceptors situated?

A

Near the surface of the medulla of the brainstem

189
Q

What do the central chemoreceptors respond to?

A

[H+] of the cerebrospinal fluid (CSF)

190
Q

What seperates the CSF from the blood?

A

The blood/brain barrier

191
Q

What is the blood-brain barrier relatively impermeable to and whayt diffuses readily across it?

A

Relatively impermeable to H+ and HCO3

CO2 diffuses readily

192
Q

Is CSF less buffered that blood?

A

Yes - contains less protein

193
Q

What is ventilation very responsive to?

A

PCO2

194
Q

In relation to the hypoxic drive of respiration: what is the effect via?

A

Peripheral chemoreceptors

195
Q

When is the hypoxic drive of respiration stimulated?

A

When arterial PO2 falls to low levels (<8.0 kPa)

196
Q

When may hypoxic drive of respiration become important?

A

In patients with chronic CO2 retention (patients with COPD)

At high altitudes

197
Q

What is hypoxia at high altitudes caused by?

A

Decreased partial pressure of inspired oxygen (PiO2)

198
Q

What are the 2 acute responses of jhypoxia at high altitudes?

A

Hyperventilation

Increased cardiac output

199
Q

What are the 5 chronic adaptions to high altitude hypoxia?

A
  1. Increased red blood cell production (polycythaemia) - O2 carrying capacity of blood increases
  2. 2,3 BPG produced within RBC - O2 offloaded more easily into tissues
  3. Increased number of capillaries - blood diffuses more easily
  4. Increased number of mitochondria - O2 can be used more efficiently
  5. Kidneys conserve acid - arteiral pH decreases
200
Q

What is the effect of the H+ drive of respiration?

A

Via the peripheral chemoreceptors

201
Q

Does H+ readily cross the blood brain barrier?

A

No (CO2 does)

202
Q

The peripheral chemoreceptors play a major role in adjusting for acidosis. What is the acidosis caused by?

A

The addition of non-carbonic acid H+ to the blood (e.g. lactic acid during exercise; and diabetic ketoacidosis)

203
Q

What does peripheral chemoreceptor stimulation by H+ cause?

A

Hyperventilation and increases elimination of CO2 from the body

(important in acid-base balance)
Remember CO2 can generate H+, so its increased elimination help reduce the load of H+ in the body)

204
Q

What does internal respiration refer to?

A

The intracellular mechanisms which consume oxygen and produce carbon dioxide.

► Med - Anatomy & Physiology (130 decks)

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