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Y1 Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

Define internal respiration

A

Intracellular mechanism which consumes O2 to produce CO2

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2
Q

Define external respiration

A

The sequence of events leading to exchange of O2 and CO2 between the external environment and the cells of the body

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3
Q

What are the 4 steps of external respiration

A

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

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4
Q

Explain the process of ventilation

A

Mechanical process of moving gas in and out of the lungs

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5
Q

State Boyle’s law

A

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

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6
Q

Why do the lungs move with the chest wall

A

Intrapleural fluid cohesivness, water molecuels in the intrapleural fluid are attached and resist seperation

The transmural pressure gradient across the lung wall and across the chest wall
(Lungs move out and chest wall moves in)

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7
Q

Explain the mechanics of inspiration

A

Diaphragm contracts increasing vertical thoracic volume (Phrenic nerve)

External intercostal muscles contract lifting ribs and moving out sternum

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8
Q

Explain the physical action of inspiration

A

As chest cavity volume increases by boyles law the pressure decreases
Air flows down its pressure gradient to restore the gradient

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9
Q

Which of normal inspiration or expiration is passive

A

Inspiration is active

Expiration if passive

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10
Q

Explain the mechanism of expiration

A

Diaphragm and intercostals relax to decrease the thoracic volume
This increases then interthoracic pressure by boyles law so, by elastic recoil air is expelled from the lungs down its pressure gradient

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11
Q

Explain the mechanism of pneumothorax

A

Traumatic the chest wall is damaged
Spontaneous the lung wall is damaged
In both cases it abolishes the transmural pressure gradient

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12
Q

What are the physical signs of pneumothorax

A

Hyperresonant percussive note

Decreased/absent breath sounds

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13
Q

What causes the lungs to recoil during expiration

A

Elastic connective tissue, lungs bounce back to original shape
Alveolar surface tension, alveolar surfactant surface tension pulls in

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14
Q

State the law of LaPlace

A

The inward pressure is relative to the surface tension and inverse to the bubble radius

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15
Q

How does LaPlace’s law apply to the lungs

A

It shows how smaller alveoli have greater tendency to collapse

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16
Q

Explain the mechanism behind respiratory distress syndrome of the newborn

A

Premature babies lack suficcient pulmonary surfactant

This causes an excessively strenuous inspiratory effort to overcome the high surface tension and inflate the lungs

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17
Q

Explain the alveolar interdependence

A

If an alveolus starts to collapse the surrounding alveoli are stretched and then recoil exerting a force to open the collapsing alveolus

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18
Q

State the major inspiratory muscle

A

Diaphragm

External intercostal muscles

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19
Q

State the accessory muscles of inspiration

A

Sternocleidomastoid
Scalenus
Pectoral

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20
Q

State the muscles of active expiration

A

Abdominal muscles and internal intercostal muscles

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21
Q

Define insipiratory capacity

A

The volume of air that can be inspired following normal passive expiration

Tidal volume + Inspiratory volume

Vital capacity - expiratory reserve volume

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22
Q

Define expiratory reserve volume

A

The volume of air which can be exhaled following normal passive exhalation

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23
Q

Define vital capacity

A

The volume of air which can be inhaled/exhaled following full exhalation/inhalation

Inspiratory capacity + expiratory reserve volume

Tidal volume + inspiratory reserve volume + expiratory reserve volume

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24
Q

Define inspiratory reserve volume

A

The volume of air which can be inhaled following normal inspiration

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25
Q

Define tidal volume

A

The volume of air moved in a normal inspiration or expiration

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26
Q

Define functional residual capacity

A

The volume of air left in lungs following normal passive expiration

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27
Q

Define residual volume

A

The volume of air remaining in the lungs following full expiration

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28
Q

Define total lung capacity

A

The maximum volume of air that can be within the lungs at any time

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29
Q

What increases the residual volume

A

When the elastic recoil of the lungs is lost

E.g emphysema

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30
Q

Define forced vital capacity

A

The maximum volume that can be forcibly expelled from the lungs following a maximum inspiration

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31
Q

Define forced expiratory volume in one second [FEV1]

A

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

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32
Q

What is the normal range for the FEV1/FVC ratio

A

Greater than 70%

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33
Q

State the equation for airway resistance

A

Flow = change in pressure over resistance

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34
Q

What is the primary factor effecting the airway resistance

A

The radius of the conducting airway

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35
Q

Explain dynamic airway compression

A

During expiration the rising pleural pressure compresses the alveoli and airway

This is overcome by the pressure downstream driving the airways open

36
Q

Explain dynamic airway compression in the case of obstructive lung disease

A

An obstruction in the airway causes a loss of the pressure downstream increasing the risk of airway collapse

This is made worse by a loss of the elastic recoil of the lungs also

37
Q

Briefly explain peak flow

A

A test useful for obstructive lung disease

38
Q

Explain pulmonary compliance

A

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

Less compliant lungs require more work to inflate to the same degree

39
Q

State some factors which decrease the pulmonary compliance

A 
Fibrosis
Oedema
Lung collapse
Pneumonia
Surfactant absence
40
Q

A decrease in pulmonary compliance results in what pattern on spirometry

A

Restrictive pattern

41
Q

State some factors which increase the pulmonary compliance

A

Old age

Emphysema

42
Q

What is a clinical sign of increased pulmonary compliance

A

Hyperinflation of the lungs

43
Q

Explain the concept of work of breathing

A 
Normal 3% of the total energy
Lungs normally operate at ~ 50% capacity
Work of breathing can increase when
- Pulmonary compliance is decreased
Airway resistance is increased
- Elastic recoil is decreased
- When a need for increased ventilation
44
Q

Define pulmonary ventilation

A

The amount of air moved between the respiratory tract and the enviroment

45
Q

Define the alveolar ventilation

A

The volume of air available for exchange at the alveoli

This is the pulmonary ventilation - anatomical dead space

46
Q

Explain anatomical dead space

A

Areas of the respiratory tract which the air is not avaliable for gas exchange

47
Q

Explain the best way to increase the pulmonary ventilation

A

Due to dead space it is more advantageous to increase the depth of breathing

48
Q

Ventilation perfusion concept

A

The amount of gas transfer is dependent on the air moving through the lungs (ventilation) and the blood flow through the lungs (perfusion)

49
Q

Explain alveolar dead space

A

The alveolar dead space are the alveolar spaces which are ventialted bur inadequately perfused

50
Q

State the physiological dead space

A

The anatomical dead space + the alveolar dead space

51
Q

State the control of V/Q matching in the lungs

A

Local controls act on smooth muscle of airways and arterioles

Accumulation of CO2 in the blood leads to increased airflow

Accumulation of O2 in the alveoli leads to increased blood flow

52
Q

What are the 4 factors which influence the rate of gas exchange across the alveolar membrane

A

Partial pressure gradient of O2 and CO2
Diffusion coefficient of O2 and CO2
Surface area of alveolar membrane
Thickness of alveolar membrane

53
Q

State Dalton’s law

A

The total pressure in a gaseous mixture is equal to the sum of the partial pressures of each individual component in the gas mixture

54
Q

Define partial pressure

A

The pressure that one gas in a mixture would exert if it were the only gas in the whole volume

55
Q

State the partial pressure of oxygen in the alveolar air

A

PaO2 = PiO2 - [PaCO2/0.8]

0.8 is the respiratory exchange rate

56
Q

How does CO2 diffuse simialr to O2 with a far lower partial pressure gradient

A

The diffusion coefficient of CO2 is ~ 20x that of O2

57
Q

State Fick’s law

A

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

58
Q

State Henry’s law

A

The amount of gas dissolved in a given type and volume of liquid at constant temprature is proportional to the partial pressure of the gas in equilibrium with liquid

59
Q

Explain O2 transport in the blood

A

A small volume is transported directly dissolved in the plasma (By Henry’s law)

Most O2 in the blood is bound to haemoglobin

60
Q

Explain the O2 binding to haemoglobin

A

Each Hb molecule contains 4 haem groups
Each haem group reversibly binds to one O2 molecule

The PO2 is the primary facotr which determines the percentage saturation of haemoglobin

Shows co-operativity, one O2 increased the affinity of Hb for O2

61
Q

Explain the Hb dissociation curve

A

The dissocaition of O2 is alosteric so forms a sigmoidal curve.

62
Q

Define the oxygen delivery index

A

Oxygen delivery to tissues is equal to the ocygen content of the arterial blood times the cardiac index (the cardiac output per the surface area of the body)

63
Q

Explain the factors on oxygen content of arterial blood

A

The Hb concentration, the % saturation of the Hb and the amount of O2 one gram of Hb can carry (1.34ml in normal)

64
Q

State the Bohr effect

A

A shift of the O2 dissociation curve to the righ, more O2 released to tissues

65
Q

State what shifts the oxygen dissociation curve to the right

A

Increased PO2
Increased H+
Increased temprature
Increased 2,3 BPG

66
Q

Briefly explain HbF

A

Foetal haemoglobin differs in structure than that of an adult

Interacts less with 2,3BPG so HbF has a higher affinity for O2

Allows O2 to transfer from mother to foetus even when PO2 is lower

67
Q

Briefly explain myoglobin

A

A protein present in the skeletal and cardiac muscles

One haem group per molecule, doesnt show co-operative binding
(Hyperbolic dissociation curve)

Myoglobin releases O2 at a very low PO2, allows a short term storage of O2 for anaerobic conditions

68
Q

What does myoglobin in the blood indicate

A

Muscle damage

69
Q

How is CO2 transported in the blood and in what proportions

A

Solution 10%
Bicarbonate 60%
Carbamino compounds 30%

70
Q

How is CO2 transported as bicarboante ions

A

CO2 + H2O by carbonic anhydrase in red blood cells forms H2CO3

H2CO3 dissociated to form H+ and HCO3-

HCO3- is exchanged for Cl- in the blood (chloride shift)

71
Q

How is CO2 transported as carbamino compounds

A

Carbamino compounds are formed by combination of CO2 with the terminal amine groups in blood proteins
(especially globin)

72
Q

Explain the Haldane effect

A

Removing O2 from Hb increases the ability of Hb to pick up CO2 and CO2 generated H+
(Shifts the curve to the left so more O2 is given up in tissues)

73
Q

Where are the major respiratory centres of the brain

A

In the medulla oblongata

Secondary in the pons: pneumotaxic and apneustic areas

74
Q

What area of the medulla acts as a pacemaker for respiration

A

Pre-Botzinger complex

Located at superior end of medullary repsiratory centre

75
Q

What is the neurological pathway to inspiration

A

Rhythm is generated by the pre-botzinger complex which excited the dorsal respiratory groups
Dorsal respiratory groups fire causing insipration, when firing stops passive expiration occurs

76
Q

What is the neurological pathway of active expiration

A

Increased firing of dorsal neurones excite a second group (ventral respiratory groups)
The action potentials from the ventral group lead to the active expiration

77
Q

How can the pons modify the rhythm to reduce inspiration

A

The pneumotaxic centre stimulated termination of inspiration
PC is stimualted when dorsal respiratory neurons fire
Apneusis with prolonged inspiratory gaps suggests PC damage

78
Q

How can the pons modify the rhythm to prolong inspiration

A

Signals from the apneustic centre excite the dorsal respiratory centre

79
Q

Explain the Hering-Breur reflex

A

Stretch receptors of the bronchi and bronchioles prevent hyperinflation

80
Q

Explain the influence of joint receptors in breathing

A

Impulses from moving limbs reflexly increase breathing

81
Q

What factors increase ventilation during exercise

A

Reflexes from body movement
Adrenaline release
Impulses from cerebral cortex
Increased body temperature

Later accumulation of CO2 and H+

82
Q

State the chemical control of respiration

A

Chemoreceptors sense the values of gas tensions

83
Q

State the location and purpose of peripheral chemoreceptors

A

Carotid bifurcation and aortic arch

Sense tension of oxygen and CO2 and H+ in the blood

84
Q

State the location and purpose of central chemoreceptors

A

Situated near the surface of the medulla of the brainstem

In response to H+ in cerebrospinal fluid

85
Q

Explain the idea of hypoxic drive

A

The effect via the peripheral chemoreceptors which is only stimulated when PO2 falls below 8kPa
Important in those with CO2 retention and at high altitudes

86
Q

Explain the H+ drive of respiration

A

This is via the peripheral chemoreceptors
Play a major role in correction of acidosis

Stimualtion by H+ causes: hyperventilation to shed CO2

Y1 Respiratory (5 decks)

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