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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

d:internal respiration

A

refers to the intracellular mechanisms which consumes O2 and produces CO2

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2
Q

d: external respiration

A

respiration refers to the sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body

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3
Q

Name the 4 steps of external respiration

A

Ventilation

exchange of O2 and CO2

Transport of O2 and CO2

Exchange of O2 and CO2 between the blood and the tissues

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4
Q

Name the 4 body systems involved in external respiration

A

respiratory
cardiovascular
haematology
Nervous

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5
Q

d: Ventilation

A

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

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6
Q

d: Boyle’s Law

A

at a constant temperature the pressure of a gas is inversely proportional to the volume of that gas

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7
Q

What way does air flow?

A

down a pressure gradient (high to low)

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8
Q

The intra-alveolar pressure be _____ than atmospheric for air to flow.

A

less

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9
Q

How is intra-alveolar pressure reduced in inhalation?

A

before inspiration, the intra-alveolar pressure=atmospheric

thorax and lungs expand as inspiratory muscles contract

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10
Q

Name the 2 forces that hold the thoracic wall and the lungs in close opposition

A
  1. Intrapleural fluid cohesiveness

2. negative intrapleural pressure

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11
Q

How do the pleural membranes stick together?

A

the h2o molecules in the intrapleural fluid are attracted to each other and resist being pulled apart

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12
Q

What creates the Transmural pressure gradient?

A

the sub-atmospheric intrapleural pressure creats gradient across both lung and chest wall.
Lungs are forced to expand outwards while the chest is forced to squeeze inwards

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13
Q

What is the transpulmonary pressure?

A

Transmural pressure gradient across lung wall

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14
Q

What is atmospheric pressure normally?

A

760mmHg

101kPa

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15
Q

Name the 3 important pressures in Ventilation

A

Atmospheric
Intra-alveolar
Intrapleural

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16
Q

Is inspiration an active or passive process?

A

active

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17
Q

Name the main nerve and the 3 smaller ones which are responsible for inspiration muscle contractions?

A

Phrenic nerve

cervical 3,4,5

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18
Q

What is the major inspiratory muscle?

A

diaphragm

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19
Q

Describe the movement of inspiration in detail

A

volume of the thorax increased vertically by contraction of the diaphragm
flattening out dome shape
the external intercostal muscle contracts and lifts ribs and moves out the sternum

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20
Q

What is a consequence of pneumothorax?

A

abolishes transmural pressure gradient needed for lung expansion.

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21
Q

d: pneumothorax

A

collapsed lung

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22
Q

Is expiration at rest an active or passive process?

A

passive

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23
Q

What does the lung recoil do?

A

makes the intra-alveolar pressure rise

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24
Q

What is the movement of the muscles that causes expiration?

A

relaxation

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25
Q

Describe muscles before inspiration

A 
external intercostal muscles relaxed
diaphragm relaxed (domed)
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26
Q

Describe muscles during inhalation

A

intercostal muscles contract
rib cage expands
diaphragm contracts moves down

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27
Q

Describe muscles during exhalation

A

rib cage gets smaller as rib muscles relax

diaphragm relaxes and moves up

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28
Q

What happens to intra-alveolar pressure on inspiration?

A

decreases below atmospheric

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29
Q

What happens to intra-alveolar pressure on expiration?

A

increases above atmospheric

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30
Q

What happens to intrapleural pressure on inspiration?

A

decreases

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31
Q

What happens to intrapleural pressure on expiration?

A

increases

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32
Q

Name the symptoms of small pneumothorax

A

shortness of breath

chest pain

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33
Q

Name the physical signs of pneumothorax

A

hyperresonant percussion note

absent/decreased breath signs

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34
Q

What causes the lungs to recoil during expiration?

A

elastic connective tissue in the lungs

alveolar surface tension

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35
Q

d: alveolar surface tension

A

Attraction between water molecules at 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 happen if the alveoli were lined with water alone?

A

the surface tension would be too strong sop the alveoli would collapse

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37
Q

f: surfactant

A

reduces alveolar surface tension

preventing smaller alveoli from collapsing and emptying their air contents into larger alveoli

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38
Q

what size of alveoli have a higher tendency to collapse? what law is this based on?

A

smaller radius alveoli

Laplace’s law

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39
Q

what is pulmonary surfactant made up of?

A

complex mixture of lipids, proteins secreted by type 2 alveoli

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40
Q

does surfactant lower surface tension of smaller alveoli more or less than that of large alveoli?

A

more

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41
Q

name a thing that causes respiratory distress syndrome in the new born

A

fetal lungs don’t develop until late pregnancy, therefore don’t synthesise surfactant until late pregnancy so premature babies wont have enough pulmonary surfactant

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42
Q

what happens to baby respiratory distress syndrome?

A

strenuous inspiratory efforts in attempt to overcome the high surface tension and inflate the lungs

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43
Q

name another factor apart from alveolar surface tension that helps keep the alveolus open

A

alveolar independence

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44
Q

describe alveolar independence

A

If an alveolus start to collapse the surrounding alveoli are
stretched and then recoil exerting expanding forces in the
collapsing alveolus to open it

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45
Q

name the 3 forces keeping the alveoli open

A

transmural pressure gradient
pulmonary surfactant
alveolar interdependence

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46
Q

name the 2 forces promoting alveolar collapse

A

elasticity of stretched lung connective tissue

alveolar surface tension

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47
Q

name the accessory muscles of forceful inspiration and whether contract or relax

A

Sternocleidomastoid, scalenus, pectoral

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48
Q

name the muscles of active expiration and whether contract or relax

A

Abdominal muscles and internal intercostal muscles

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49
Q

Name the muscles that contract and relax every inspiration and passive expiration respectively

A

diaphragm

external intercostal muscles

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50
Q

What does IC stand for? and avg value in young adult male?

A

inspiratory capacity

3.5LWhat does IC stand for? and avg value in young adult male?

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51
Q

What does TV stand for? and avg value in young adult male?

A

Tidal Volume

0.5L

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52
Q

What does IRV stand for? and avg value in young adult male?

A

Inspiratory Reserve Volume

3.0L

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53
Q

What does VC stand for? and avg value in young adult male?

A

Vital Capacity

4.5L

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54
Q

What does ERV stand for? and avg value in young adult male?

A

Expiratory Reserve Volume

1.0L

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55
Q

What does FRC stand for? and avg value in young adult male?

A

Functional Residual Capacity

2.2L

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56
Q

What does RV stand for? and avg value in young adult male?

A

Residual Volume

1.2L

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57
Q

What does TLC stand for? and avg value in young adult male?

A

Total lung Capacity

5.700L

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58
Q

d: Tidal Volume

A

Volume of air entering or leaving lungs during a single breath

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59
Q

d: Inspiratory reserve volume

A

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

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60
Q

d: Expiratory reserve volume

A

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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61
Q

d: residual volume

A

Minimum volume of air remaining in the lungs even after a maximal expiration

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62
Q

d: inspiratory capacity and equation

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)

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63
Q

d: functional residual capacity

A

Volume of air in lungs at end of normal passive expiration

(FRC = ERV + RV)

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64
Q

d: Vital Capacity

A

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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65
Q

d: Total Lung Capacity

A

Total volume of air the lungs can hold

TLC = VC + RV

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66
Q

What respiratory volume cannot be measure by spirometry?

A

residual

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67
Q

Why is it not possible to measure Total Lung Volume by spirometry?

A

as residual cannot be measured by it, still air in lungs

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68
Q

what happens to residual volume of thee lungs in emphysema?

A

increases when the elastic recoil of the lungs is lost

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69
Q

Name the 3 things a volume time curve can tell you

A

Forced Vital Capacity (FVC)
FEV1 = Forced Expiratory volume in one second
FEV1/FVC ratio

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70
Q

What are dynamic lung volumes useful for diagnosis?

A

obstructive and restrictive lung disease

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71
Q

d: forced vital capacity

A

maximum volume that can be forcibly

Expelled from the lungs following a maximum inspiration

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72
Q

d: forced expiratory volume in 1 second

A

Volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination.

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73
Q

d:FEV1/FVC ratio

A

The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) X 100%

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74
Q

What is the FEV1/FVC ratio more than?

A

70%

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75
Q

what is the equation for airway resistance?

A

flow=change in pressure/resistance

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76
Q

Why does air move with a small pressure gradient?

A

resistance to flow in airway is normally very low

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77
Q

what is the primary determinant of airway resistance?

A

radius of the conducting airway

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78
Q

what stimulation causes bronchoconstriction?

A

parasympathetic

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79
Q

what stimulation causes bronchodilatation?

A

sympathetic

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80
Q

what 2 diseases cause significant resistance to air flow?

A

COPD

Asthma

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81
Q

which is more difficult with increased resistance, inspiration or expiration?

A

expiration

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82
Q

What happens to airways on inspiration? what happens to the intrapleural pressure?

A

airways are pulled open by the expanding thorax

falls

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83
Q

what happens during expiration to airways and intrapleural pressure?

A

chest recoils, airways back to og

rises

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84
Q

d: dynamic airway compression

A

when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways.

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85
Q

What happens in dynamic airway compression?

A

Pressure applied to alveolus helps
pushes air out of lungs
The rising pleural pressure during active expiration compresses the alveoli and airway
Pressure applied to airway is not desirable - tends to compress it
makes active expiration to be more difficult in patients with airway obstruction

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86
Q

what does increased airway resistance causing an increase in airway pressure help? upstream

A

open the airways by increasing the driving pressure between the alveolus and airway

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87
Q

What does an obstruction in the airway do to the dynamic airway compression?

A

the driving pressure between the alveolus and airway is lost over the obstructed segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration
more likely to collapse

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88
Q

what does a peak flow meter do?

A

gives estimate peak flow rate, assessing airway function

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89
Q

d; pulmonary compliance

A

Compliance is measure of effort that has to go into stretching or distending the lungs
or

Volume change per unit of pressure change across the lungs

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90
Q

what happens when lungs are less compliant?

A

the more work is required to produce a given degree of inflation

91
Q

name some factors which decrease pulmonary compliance

A

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

92
Q

what does decreased pulmonary compliance mean for patient?

A

means 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

93
Q

What does decreased pulmonary compliance mean in a spirometer?

A

may cause a restrictive pattern of lung volumes

94
Q

When may compliance become abnormally increased?

A

elastic recoil of the lungs is lost eg. emphysema

95
Q

What % of total energy expenditure is required for quiet breathing?

A

3%

96
Q

How full do lungs normally work at?

A

half full

97
Q

name the 4 situations when the work of breathing is increased?

A

When pulmonary compliance is decreased
When airway resistance is increased
When elastic recoil is decreased
When there is a need for increased ventilation

98
Q

what is anatomical dead space?

A

where some of the inspired air remains in airways, not available for gas exchange

99
Q

What is pulmonary ventilation equal to?

A

tidal volume X respiratory rate

100
Q

why is alveolar ventilation less than pulmonary ventilation?

A

presence of dead space

101
Q

equation for alveolar ventilation?

A

(tidal volume – dead space volume) x Respiratory Rate

102
Q

d: pulmonary ventilation

A

Is the volume of air breathed in and out per minute

103
Q

d: alveolar ventilation

A

Is the volume of air exchanged between the atmosphere and alveoli per minute

104
Q

Which ventilation represents the new air available for gas exchange with blood?

A

alveolar

105
Q

How is pulmonary ventilation increased and why is this more advantageous?

A

INCREASED depth of breathing (TV) and
rate of breathing (RR)

because of dead space

106
Q

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

A

ventilation

perfusion

107
Q

d: ventilation

A

the rate at which gas is passing through the lungs.

108
Q

d: perfusion

A

the rate at which blood is passing through the lungs

109
Q

why are the avg arterial and alveolar partial pressures of O2 not exactly the same?

A

Both blood flow and ventilation vary from bottom to top of the lung

110
Q

what are Ventilated alveoli which are not adequately perfused with blood are considered as?

A

alveolar dead space

111
Q

what is the physiological dead space equal to?

A

the anatomical dead space + the alveolar dead space

112
Q

what would happen to the alveolar dead space in disease?

A

increase significantly

113
Q

What matches airflow to blood flow?

A

Local controls act on the smooth muscles of airways and arterioles

114
Q

What does the accumulation of CO2 n alveoli as a result of increased perfusion do?

A

decreases airway resistance leading to increased airflow

115
Q

What causes pulmonary vasodilation, which increases blood flow to match larger airflow?

A

increasing alveolar O2 conc. as a result of increased ventilation

116
Q

Describe what happens in an area in which perfusion (rate of blood flow) is greater than ventilation (rate of airflow)

A 
C02 increases in area
O2 decreases
dilation of local airways
constriction of local blood vessels
airflow increase
BF decreases
117
Q

Describe what happens in an Area in which ventilation (rate of airflow) is greater than perfusion (rate of blood flow)

A 
CO2 decreases in the area
O2 increases in the area
Constriction of local airways
dilation of local BV
airflow decrease
BF increase
118
Q

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

A

Partial Pressure Gradient of O2 and CO2
Diffusion coefficient for O2 and CO2
Surface area of alveolar membrane
Thickness of alveolar membrane

119
Q

d: partial pressure of gas

A

the pressure that a gas in a mixture of gases would exert if it occupied the same volume as the mixture at a certain temperature

120
Q

What is Dalton’s Law

A

The Total Pressure exerted by
a gaseous mixture =

The sum of the partial pressures of
each individual component in
the gas mixture

121
Q

how do gases move across cell membranes?

A

via pressure gradient

122
Q

what determines the pressure gradient for a gas?

A

partial pressure

123
Q

Give the alveolar gas equation

A

PAO2(partial pressure of oxygen in the alveolar air)= PiO2(partial pressure of inspired air) -[PaCO2(partial pressure of CO2 in arterial Blood)/0.8]

124
Q

What is the 0.8 in the alveolar gas equation?

A

Respiratory Exchange Ratio (RER)

i.e. ratio of CO2 produced/O2 consumed

125
Q

What is the air in the respiratory tract saturated with? How much does this contribute to the total pressure of the lungs?

A

water

47mmHg

126
Q

Why is the partial pressure gradient for CO2 smaller than O2?

A

CO2 more soluble in membranes than O2

127
Q

d: the diffusion coefficient

A

The solubility of gas in membranes

128
Q

What would a BIG gradient between PAO2 and PaO2(arterial) indicate? Why?

A

problems with gas exchange in the lungs or a right to left shunt in the heart
as normally its a small gradient

129
Q

d: Fick’s Law of Diffusion

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
130
Q

Give adaptions lungs that increase gas exchange

A 
LSA in THIN membranes
airway divides repeatedly to increase SA
alveoli
extensive capillary network
pulmonary circulation receives the ENTIRE cardiac output
131
Q

describe composition of alveoli

A

thin-walled inflatable sacs

1 layer of flattened type I alveolar cells

132
Q

where are pulmonary capillaries found?

A

encircling each alveolus

133
Q

Name some non-respiratory functions of the respiratory system

A

route for water loss and heat elimination

enhances venous return

maintains normal acid-base balance

speech, singing etc

defends against inhaled foreign matter

nose organ of smell

removes, modifies, activates or inactivates various materials passing through pulmonary circulation

134
Q

What happens to the O2 picked up by the blood at the lungs?

A

must be transported in the blood to the tissues for cellular use

135
Q

What happens to the CO2 produced at the tissues?

A

must be transported in the blood to the lungs for removal from the body

136
Q

d: Henry’s Law

A 
The amount of a given gas dissolve 
in a given type and volume of liquid 
(e.g. blood) at a constant 
temperature is: 
proportional to the partial pressure 
of the gas in equilibrium with the 
liquid
137
Q

How is most O2 in the blood transported?

A

vis binding to haemoglobin in the red blood cells

138
Q

What is the percentage of O2 carried bound to haemoglobin?

A

98.5%

139
Q

What is the percentage of O2 carried in the dissolved form? and how much is this in litres?

A

1.5%

3ml per L at PO2 of 13.3kPa

140
Q

Name the 2 forms O2 is present in the blood with

A

bound to haemoglobin

physically dissolved

141
Q

haemoglobin combined with O2 is a reversible/irreversible combination?

A

reversible

142
Q

How many haem groups are there in a haemoglobin molecule?

A

4

143
Q

how many O2 groups can bind to each HAEM GROUP?

A

1

144
Q

When is Hb fully saturated?

A

when all the Hb present is carrying its maximum O2 load

145
Q

What is the primary factor which determines the % saturation of haemoglobin with O2?

A

Po2

146
Q

What Cation does O2 molecule bind to in Hb?

A

Fe2+

147
Q

What shape is the Oxygen Haemoglobin Dissociation Curve and why?

A

sigmoidal it plateaus because all sites are becoming occupied

148
Q

d: Oxygen Delivery Index

A

a function of oxygen content of arterial blood and the cardiac output

149
Q

What does CaO2 stand for? units

A

Oxygen content of arterial blood (ml/L)

150
Q

What does DO2I mean? units

A

Oxygen Delivery Index (ml/min/metre2)

151
Q

what is the O2 content of arterial blood is determined by?

A

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

152
Q

How much O2 can 1 gram of Hb, when fully saturated, carry?

A

1.34ml

153
Q

Name 3 disease areas that can impair oxygen delivery to the tissues

A

respiratory disease
heart failure
anaemia

154
Q

name 2 things the partial pressure of inspired O2 depends on

A

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

155
Q

What factor do you multiply kPa by to get it in mmHg?

A

7.5

156
Q

How do respiratory diseases impair O2 delivery to tissues?

A

Decreased partial pressure of inspired oxygen
These can decrease arterial PO2 and hence decrease
Hb saturation with O2 and O2 content of the blood

157
Q

How does anaemia impair O2 delivery to tissues?

A

This decreases Hb concentration and hence decreases

O2 content of the blood

158
Q

How does Heart failure impair O2 delivery to tissues?

A

decreases cardiac output

159
Q

What increases the affinity of Hb for O2?

A

Binding of one O2 to Hb

160
Q

What is the significance of the flat upper portions of the sigmoid curve, for a change in alveolar Po2?

A

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

161
Q

What is the significance of the steeper lower part of the sigmoid curve, for a change in alveolar Po2?

A

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

162
Q

What is the Bohr effect and what change does this induce on the sigmoid curve?

A

release of O2 by conditions of the tissue (e.g. ^CO2, ^H+, ^temp) leads to shift of the curve to the right, This means more oxygen is released.

163
Q

Name 4 conditions that increase release of O2

A 
increase in:
Pco2
[h+]
temp
2,3-Biphosphoglycerate
164
Q

Which has greater affinity for O2 binding, foetal/adult Hb? Why?

A

HbF has 2 alpha and 2 gamma units

also interacts less with 2,3- Biphosphoglycerate in red blood cells, hence higher affinity

165
Q

Is the HbF O2-Hb dissociation curve shifted to the left or right of HbA?

A

left

166
Q

What does the high O2 affinity for allow HbF to do for foetus?

A

This would allow O2 to transfer from mother to foetus even if the PO2 is low

167
Q

What muscles is Myoglobin present in?

A

skeletal

cardiac

168
Q

How many haem groups in myoglobin?

A

1

169
Q

What shape of curve is the dissociation curve? Why?

A

hyperbolic

no cooperative binding of O2

170
Q

Myoglobin releases O2 at low/high PO2?

A

low

171
Q

f: myoglobin

A

Provides a short-term storage of O2 for anaerobic conditions

172
Q

what does the presence of myoglobin in blood indicate?

A

muscle damage

173
Q

Name the 3 ways CO2 is transported in the blood and %

A

solution 10%
bicarbonate 60%
carbamino compounds 30%

174
Q

How is bicarbonate formed and where?

A

In this system, carbon dioxide diffuses into the red blood cells
Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions
(HCO3)
(HCO3−)
and hydrogen (H+) ions

175
Q

d: Haldane effect

A

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

176
Q

Why is CO2 carried in solution

A

20x more soluble than 02

177
Q

what is equation for bicarbonate formation?

A

CO2 + H2O H2CO3 H+ +HCO3-

178
Q

How are carbamino compounds formed?

A

Carbamino compounds formed by combination of CO2 with terminal amine groups in blood proteins.
Especially globin of haemoglobin to give carbamino-haemoglobin

179
Q

Why can reduced Hb bind more CO2 than Hb02?

A

O2 has be lost therefore more room

180
Q

How do Boher and Haldane effect work in synchrony?

A

O2 liberation and uptake of CO2 & CO2 generated H+ at tissues

181
Q

Explain the boher-haldane effect at the lungs;

A

At the lungs the Hb pick-up the O2

This weaken its ability to bind CO2 and H+

182
Q

what is the major rhythm generator in respiring and why?

A

medulla

ventilation ceases below medulla section of brain and remains fairly normal above the medulla

183
Q

what is the normal rhythm of respiration?

A

inspiration followed by expiration

184
Q

what network of neurones generates breathing rhythm? Where are they located?

A

pre-botzinger complex

upper end of the medullary respiratory centre

185
Q

describe the neural process that gives rise to inspiration

A

Rhythm generated by Pre-Botzinger complex
Excites Dorsal respiratory group neurones (inspiratory)
Fire in bursts
Firing leads to contraction of inspiratory muscles - inspiration

186
Q

what happens when firing of dorsal neurones stops?

A

passive expiration

187
Q

describe what happens neurally during active expiration during hyperventilation?

A

Increased firing of dorsal neurones excites a second group:
Ventral respiratory group neurones
Excite internal intercostals, abdominals etc leads to forceful expiration

188
Q

What do the ventral neurones NOT do in quiet breathing?

A

activate expiratory muscles

189
Q

By what can the rhythm generated in the medulla be modified by?

A

the neurones in the pons

190
Q

describe the process by with the rhythm generated in the medulla be modified by the neurones in the pons

A

Pneumotaxic Centre” (PC)
Stimulation terminates inspiration
PC stimulated when dorsal respiratory neurones fire
Inspiration inhibited

191
Q

what would happen without the PC?

A

breathing is prolonged inspiratory gasps with brief expiration - APNEUSIS

192
Q

d: apneusis

A

is an abnormal pattern of breathing characterized by deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release.

193
Q

f: apneustic centre

A

Impulses from these neurones excite inspiratory area of medulla
Prolong inspiration

194
Q

Name the 7 receptors that influence respiratory centres

A

Higher brain centres e.g. cerebral cortex, limbic system, hypothalamus
Stretch receptors in the walls of bronchi and bronchioles
Juxtapulmonary (J) receptors
joint receptors
baroreceptors
central chemoreceptors
peripheral chemoreceptors

195
Q

what are juxtapulmonary receptors stimulated by?

A

pulmonary capillary congestion and pulmonary oedema (caused by e.g. left heart failure)

196
Q

what is a characteristic symptom of pulmonary embolism?

A

rapid shallow breathing

197
Q

name 4 examples of involuntary modifications of breathing

A

pulmonary stretch receptors eg hering-breuer reflex
joint receptors in exercise
stimulation of respiratory centre in temperature, adrenaline, or impulses from cerebral cortex
cough reflex

198
Q

describe how pulmonary stretch receptors become activated during inspiration and eg

A

afferent discharge inhibits inspiration Hering- Breuer reflex

199
Q

do pulmonary stretch receptors switch off during normal respiratory cycle?

A

unlikely, only activated at large greater than 1L tidal volumes

200
Q

how do joint receptors increase breathing and what else do they do?

A

Impulses from moving limbs reflexly increase breathing

Probably contribute to the increased ventilation during exercise

201
Q

Name the factors that may increase ventilation during exercise

A 
reflexes from body movt
adrenaline release
impulses from the cerebral cortex
increase in body temp
later on: accumulation of CO2 and H+ generated by active muscles
202
Q

what does cough reflex do to modify breathing?

where is its control mechanism?

A

vital part of body defence mechanisms
clears airway of dust
medulla

203
Q

describe the mechanism of a cough?

A

Afferent discharge stimulates: short intake of breath, followed by closure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsion of air at a high speed

204
Q

what is an example of negative feedback control in respiration? what are the controlled variables in this and what senses these?

A

chemical control of respiration
controlled variables are the blood gas tensions, especially carbon dioxide

Chemoreceptors

205
Q

f: peripheral chemoreceptors and egs

A

Sense tension of oxygen and carbon dioxide;
and [H+] in the blood

carotid and aortic bodies

206
Q

where are central chemoreceptors found?

A

near the surface of the medulla

207
Q

f: central chemoreceptors

A

Respond to the [H+] of the cerebrospinal fluid (CSF)

208
Q

how is CSF seperated to blood and what happens at it?

A

blood-brain barrier
Relatively impermeable to H+ and HCO3-
CO2 diffuses readily

209
Q

why is CSF less buffered than blood?

A

contains less protein than blood

210
Q

d: hypercapnia

A

excessive carbon dioxide in the bloodstream, typically caused by inadequate respiration

211
Q

how is hypercapnia generated?

A

central chemoreceptors

212
Q

d: hypoxia

A

inadequate oxygen supply at tissue level

213
Q

what receptors are stimulated during hypoxia?

A

peripheral chemoreceptors

214
Q

at what partial o2 pressure are peripheral chemoreceptors stimulated?

A

lower than 8kPa

215
Q

when is hypoxic drive most prevalent in patients?

A

in patients with chronic CO2 retention (e.g. patients with COPD)

at high altitudes

216
Q

how is hypoxia at high altitudes caused?

A

Decreased partial
pressure of inspired
Oxygen (PiO2)

217
Q

what is the body’s acute response to high altitude induced hypoxia?

A

hyperventilation and increased cardiac output

218
Q

what are the symptoms of acute mountain sickness?

A

headache, fatigue, nausea, tachycardia, dizziness, sleep disturbance, exhaustion, shortness of breath, unconsciousness

219
Q

name the chronic adaptions to high altitude hypoxia

A 
increased RBC production
increased 2,3 BPG produced within RBC
increased number of capillaries
increased number of mitochondria
kidneys conserve acid making the arterial pH less
220
Q

true/false

H+ readily crosses the blood brain barrier

A

false

221
Q

what receptors adjust acidosis?

A

peripheral chemoreceptors play a major role in adjusting for acidosis caused by the addition of non-carbonic acid H+ to the blood

222
Q

how do peripheral chemoreceptors affect acidosis?

A

Their stimulation by H+ causes hyperventilation and increases elimination of CO2 from the body (remember CO2 can generate H+, so its increased elimination help reduce the load of H+ in the body)

223
Q

what effect does severe hypoxia have on the respiratory centre?

A

depresses it

Respiratory (27 decks)

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