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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

Internal respiration

A

Intracellular mechanisms which consume O2 and produce CO2

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2
Q

External respiration

A

Sequence of events that leads to the exchange of O2 and CO2 between body cells and external environment

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3
Q

4 steps of external respiration

A
  1. Ventilation - the mechanical process of moving gas in and out of the lungs
  2. Exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries
  3. Transport of O2 and CO2 in the circulating blood (between lungs and tissues)
  4. Exchange of O2 and CO2 between the blood and the tissues
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4
Q

4 body systems involved in external respiration

A

Respiratory
Cardiovascular
Haematology system
Nervous system

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5
Q

What is ventilation

A

Mechanical process of moving air between the atmosphere and alveolar sacs

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6
Q

What is Boyle’s law

A

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

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7
Q

What is atmospheric pressure

A

Pressure caused by the weight of the gas in the atmosphere on the earths surface

760mmHg

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8
Q

What is intra-alveolar pressure

A

Pressure within the lung alveoli

760mmHg

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9
Q

What is intrapleural pressure

A

Pressure exerted outside the lungs within pleural cavity

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10
Q

Negative intrapleural pressure

A

The sub-atmospheric intrapleural pressure (intra-thoracic pressure) creates a transmural pressure gradient across the lung wall and across the chest wall

Means lungs expand outwards while chest squeezes inwards

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11
Q

Intrapleural cohesiveness

A

Water molecules in intrapleural fluid are attached to each other and resist being pulled apart

Pleural membranes stick together

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12
Q

How do you convert between mmHg and kilopascals

A

Divide by 7.5

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13
Q

4 steps of inspiration

A
  1. Diaphragm contracts and descends, increasing vertical chest dimension
  2. External intercostal muscle lifts the ribs and moves out the sternum → increased volume of thorax
    Bucket handle mechanism
  3. Lung size increases so intra-alveolar pressure decreases (Boyle’s Law)
  4. Air enters the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to atmospheric pressure
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14
Q

What is the difference in force inspiration compared to normal inspiration

A

Forced has:
- greater outflow of action potentials of longer duration causing maximal descension and flattening
- intercostal muscles contract forcefully to raise ribs maximally
- accessory muscles

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15
Q

What are the accessory muscles of inspiration

A

Pectoralis major
Pectoralis minor
Sterocleidomastoid
Scalenus anterior, medius, and posterior

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16
Q

3 steps of expiration

A
  1. Diaphragm relaxes and rises, intercostal muscles contract
  2. Intra-alveolar pressure increases (Boyle’s Law)
    Caused by relaxation of inspiratory muscles → passive process
  3. Lungs recoil to expell air from the lungs down its pressure gradient until the intra-alveolar pressure becomes equal to atmospheric pressure
    Due to alveolar tension
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17
Q

Difference in forced expiration and normal respiration

A

In forced:
- right and left anterolateral abdominal wall muscles contract forcefully, increasing intra-abdominal pressure
- diaphragm forced superiorly by compressed abdominal contents
- Intrathoracic pressure increases, air moves from high to low pressure - out of lungs

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18
Q

What is alveolar surface tension

A

Attraction between water molecules at liquid air interface

Produces a force which resists stretching of the lungs in alveoli helping lungs to recoil during expiration

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19
Q

Law of LaPlace

A

Inward collapsing pressure is equal to 2x surface tension divided by radius

P = 2T / r

Means smaller alveoli are more likely to collapse

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20
Q

What is lung surfactant

A

Complex mixture of lipids and proteins secreted by type 2 alveoli

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21
Q

What does lung surfactant do

A

Intersperses water molecules lining alveoli reducing alveolar surface tension to prevent collapse

Lowers surface tension of smaller alveoli more than larger alveoli to prevent collapse at end of expiration

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22
Q

What is respiratory distress syndrome of the newborn

A

Developing fetal lungs are unable to synthesise surfactant until late pregnancy

There’re premature babies may not have enough pulmonary surfactant

At birth baby make strenuous inspiratory effects to overcome high surface tension and inflate lungs which can cause damage

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23
Q

What are the forces keeping the alveoli open

A

Transmural pressure gradient

Pulmonary surfactant

Alveolar interdependence

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24
Q

What is alveolar interdependence

A

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

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25
Q

What forces promote alveolar collapse

A

Elastic recoil of lungs and chest wall

Alveolar surface tension

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26
Q

What are the major inspiratory muscles

A

Diaphragm

External intercostal muscles

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27
Q

Accessory muscles of inspiration

A
  • Sternocleidomastoid
  • Scalenus
  • Pectoral
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28
Q

Muscles of active expiration

A
  • Abdominal muscles
  • Internal intercostal muscles
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29
Q

4 lung volumes

A

Tidal volume - TV
Inspiratory reserve volume - IRV
Expiratory reserve volume - ERV
Residual volume - RV

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30
Q

4 lung capacities

A

Vital capacity
Inspiratory capacity - IC
Functional residual capacity - FRC
Total lung capacity - TLC

31
Q

Tidal volume

A

Volume that enters and leave with each breath

Normal quiet inspiration and expiration

32
Q

Inspiratory reserve volume

A

Amount of air that can be forcibly inhaled after a normal tidal volume

Relies on; muscle strength, lung compliance (elastic recoil) and normal starting point

33
Q

Expiratory reserve volume

A

The volume of air that can be exhaled forcibly after exhalation of normal tidal volume

Flies on muscle strength and low airway resistance

34
Q

Residual volume

A

Volume of air remaining in lungs after maximal exhalation

Increases when elastic recoil of lungs is lost

Cannot be measured by spirometry

35
Q

Vital capacity

A

Volume that can be exhaled after maximum inspiration

VC = IRV + TV + ERV

36
Q

Inspiratory capacity

A

Volume that can be inhaled after quiet exhalation

IC = IRV + TV

37
Q

Functional residual capacity

A

Volume of air in lungs at end of normal passive expiration

FRC = ERV + RV

38
Q

Total lung capacity

A

Volume of air in lungs after maximal inspiration

Sum of all volumes

39
Q

What do you call a graph that plots volume against time using data from spirometry test

A

Vitalograph

40
Q

2 important spirometry volumes on Vitograph

A

Forced vital capacity (FVC)
- maximum volume of air subject can expel in maximal expiration from maximal inspiration

Forced expiratory volume in 1 second (FEV1)
- the maximal volume of air that a subject can expel in one second from point of maximum inspiration

41
Q

In obstructive lung diseases what happens FVC and FEV1

A

FVC is only reduced slightly

FEV1 <80% of predicted

42
Q

In restrictive lung diseases what happens FVC and FEV1

A

Both <80% of predicted

43
Q

Airway resistance equation

A

F = ∆P / R

∆P = pressure gradient
R = radius

44
Q

Which type of stimulation normally causes bronchoconstriction

A

Parasympathetic

45
Q

Which type of stimulation normally causes bronchodilation

A

Sympathetic

46
Q

What is dynamic airway compression

A

In active expiration lungs are compressed so air is pushed out of alveoli and airway

47
Q

What is pulmonary compliance

A

The measure of effort that goes into stretching lungs. Volume change per unit of pressure change across lungs

48
Q

Lungs normally operate at 1/2 full.
What causes work of breathing to increase (4)

A

Pulmonary compliance decreased
Airway resistance increased
Elastic recoil decreased
Increased need for ventilation

49
Q

Pulmonary ventilation

A

Volume of air breathed in and out per minute

  • tidal volume x respiratory rate
50
Q

Alveolar respiration

A

Volume of air exchanged between the atmosphere and alveoli per minute

  • (tidal volume - dead space) x respiratory rate
51
Q

Anatomical dead space

A

Airways that fill but cannot perform gas exchange

52
Q

Definition of Ventilation

A

Rate at which gas is passing through the lungs

53
Q

Perfusion

A

Rate at which blood is passing through the lungs

54
Q

Ventilation and perfusion (Q) at apex (top) of lung

A

Good V but poor Q

55
Q

Ventilation and perfusion at base of lung

A

Poor V but good Q

56
Q

What is alveolar dead space

A

Ventilated alveoli which are not adequately perfused with blood

57
Q

What happens when perfusion is greater than ventilation

A

CO2 increases
- vasodilation of airways :. Airflow increases

O2 decreases
- Vasoconstriction of local blood vessels :. Blood flow decreases

58
Q

What happens when ventilation is greater than perfusion

A

CO2 decreases
- Vasoconstriciton of airways :. Airflow decreases

O2 increases
- Vasodilation of local blood vessels :. Blood flow increases

59
Q

4 factors that affect rate of gas exchange

A

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

60
Q

What is the equation for partial pressure of oxygen in alveolar air

A

PAO2 = PiO2 - PaCO2 / 0.8

61
Q

What is the difference between CO2 diffusion coefficient and O2 coefficient

A

CO2 coefficient is 20x O2 coefficient

62
Q

What are the non-respiratory functions of the respiratory system

A

Water loss and heat elimination
Enhances venous return
Helps maintain normal acid-base balance
Speech
Smell
Defence against inhaled foreign material

63
Q

What is Henrys law of partial pressure

A

The amount of a given gas dissolved 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

64
Q

What are the two ways oxygen is transported around the body

A

Dissolved in blood (1.5%)
Attached to haemoglobin (98.5%)

65
Q

How is Oxygen delivery index calculated

A

DO2I = CaO2 x Ci

CaO2 - O2 consent of arterial blood
Ci = function of cardiac output (cardiac index)

66
Q

How is Oxygen content of arterial blood calculated

A

CaO2 = 1.34 x [Hb] x SaO2

1 gram of [Hb] can carry 1.34ml of O2 when fully saturated

SaO2 = %[Hb] saturated with O2

67
Q

How is foetal haemoglobin different to adult haemoglobin

A

Differs in structure - 2 alpha and 2 gamma haem groups

Has higher affinity for O2 compared to adult haemoglobin so that O2 can transfer from mother to foetus

68
Q

What is Myoglobin

A

Oxygen carrier present in skeletal and cardiac muscle
Only has one haem group per molecule

Releases oxygen at very low PO2

Short term storage of oxygen in anaerobic conditions

69
Q

What causes oxygen delivery to tissue to be impaired

A

Decreased partial pressure - at altitude

Respiratory diseases - decreased arterial PO2

Anaemia - decreased Hb conc

Heart failure - decreased CO

70
Q

What are the 3 ways CO2 is transported in the blood ?

A

In solution (10%)
Carb amino compounds (30%)
(Includes haemaglobin)
Bicarbonate (60%)

71
Q

What is the Haldane effect

A

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

72
Q

What is bicarbonate converted into in RBCs

What enzyme converts this product to CO2

A

Carbonic acid

Carbonic anhydrase

73
Q

What is the network of neurones in the medulla that is believed to generate breathing rhythm

A

Pre-Botzinger complex

74
Q

What are the 8 stimuli that influence respiratory centres

A

Higher brain centres
Stretch receptors
Juxtapulmonary receptors
Joint receptors
Exercise
Baroreceptors
Chemoreceptors
Cough reflex

Respiratory (2 decks)

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