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Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

3 pressures important in ventilation

A

Atmospheric Pressure
Intra-alveolar (intra pulmonary) Pressure
Intra-pleural (intrathoracic) pressure

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2
Q

Inspiration

A

An active process brought about by contraction of inspiratory muscles

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3
Q

Expiration

A

A passive process brought about by relaxation of inspiratory muscles

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4
Q

Changes in intra-alveolar and intra-pleural pressures during the respiratory cycle

A

Falls during inspiration, rises during expiration.

transmural pressure gradient remains relatively constant

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5
Q

Pneumothorax

A

Air in the pleural space

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6
Q

What causes the lungs to recoil during expiration?

A

Elastic connective tissue in the lungs

Alveolar Surface Tension

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7
Q

Pulmonary Surfactant

A

A complex mixture of lipids and proteins secreted by type 2 alveoli.
Lowers alveoli surface tension by interspersing between the water molecules lining the alveoli.

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8
Q

Alveolar Interdependence

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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9
Q

Forces keeping the alveoli open (3)

A

Alveolar Interdependence
Pulmonary Surfactant
Transmural Pressure Gradient

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10
Q

Forces promoting alveolar collapse (2)

A

Elasticity of stretched lung connective tissue

Alveolar surface tension

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11
Q

Major inspiratory muscles

A

Diaphragm

External intercostal muscles

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12
Q

Accessory muscles of inspiration

A

Sternocleidomastoid
Scalenus
Pectoral

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13
Q

Muscles of active expiration

A

Abdominal muscles

Internal intercostal muscles

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14
Q

Tidal Volume (TV) and avg value

A

Volume of air entering or leaving lungs during a single breath
0.5L

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15
Q

Inspiratory Reserve Volume (IRV) and avg value

A

Extra volume of air that can be maximally inspired over and above typical resting tidal volume
3.0L

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16
Q

Expiratory Reserve Volume (ERV) and avg value

A

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
1.0L

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17
Q

Residual Volume (RV) and avg value

A

Minimum volume of air remaining in the even after a maximal expiration
1.2L

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18
Q

Inspiratory Capacity (IC) + avg volume

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration
3.5L
(IC= TV+IRV)

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19
Q

Functional Residual Capacity (FRC)

A

Volume of air in lungs at end of normal passive expiration
2.2L
(FRC = ERV + RV)

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20
Q

Vital Capacity (VC)

A

Maximal volume of air that can be moved out during a single breath following a maximal inspiration
4.5L
(VC= IRV+TV+ERV)

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21
Q

Total Lung Capacity (TLC)

A

Total volume of air the lungs can hold
5.7L
(TLC=VC+RV)

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22
Q

Normal FEV1/FVC ratio

A

> 70%

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23
Q

Intrapleural pressure during inspiration and expiration

A

Falls during inspiration

Rises during expiration

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24
Q

Peak flow rate

A

Velocity at which you can breathe out of lungs

Used to assess airway function

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25
Q

Pulmonary compliance

A

Measure of effort that has to go into stretching or distending the lungs
Volume change per unit of pressure change across the lungs

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26
Q

Factors which decrease pulmonary compliance (5)

A

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

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27
Q

Factors which increase pulmonary compliance

A

elastic recoil of lungs is lost-emphysema

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28
Q

Pulmonary Ventilation

A

Tidal volume x respiratory rate

The volume of air breathed in and out per minute

29
Q

Alveolar Ventilation

A

(Tidal volume-dead space volume) x respiratory rate

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

30
Q

Ventilation Perfusion Match

A

Local controls act on the smooth muscles of airways and arterioles to match airflow to blood flow

31
Q

Four factors which influence rate of gas exchange across 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

32
Q

What would a big gradient between PAO2 (alveolar) and PaO2 (arterial) indicate?

A

Problems with gas exchange in the lungs

Right to left shunt in the heart

33
Q

Non-respiratory functions of respiratory system (7)

A

Route for water loss and heat elimination
Enhances venous return
Helps maintain normal acid-base balance
Enables speech, singing and other vocalisations
Defends against inhaled foreign matter
Removes, modifies, activates or inactivates various materials passing through pulmonary circulation
Nose serves as the organ of smell

34
Q

Oxygen delivery index (DO2l)

A

Oxygen content of arterial blood(CaO2) x Cardiac index (CI)

35
Q

What determines the oxygen content of arterial blood

A

The haemoglobin concentration [Hb] and the saturation of Hb with O2
CaO2 = 1.34 x [Hb] x SaO2

36
Q

Factors that affect oxygen delivery to the tissues (4)

A

Decreased partial pressure of inspired oxygen
Anaemia (decreases Hb concentration and hence decreases O2 content of the blood)
Heart Failure (decreases cardiac output)
Respiratory disease(decrease arterial PO2 hence decrease Hb saturation with O2 and O2 content of blood)

37
Q

Function of myoglobin

A

Provides a short-term storage of O2 for anaerobic conditions

Present in skeletal and cardiac muscles

38
Q

Means of CO2 transport in the blood

A

Solution (10%)
As bicarbonate (60%)
As carbamino compounds (30%)

39
Q

What is the effect of partial pressure on gas solubility?

A

If the partial pressure in the gas phase is increased the concentration of the gas in the liquid phase would increase proportionally

40
Q

How are carbamino compounds formed?

A

Combination of CO2 with terminal amine groups in blood proteins

41
Q

How is bicarbonate formed in the blood?

A

Co2 diffuses from capillaries into red blood cells where it reacts with water in the presence of carbonic anhydrase to produce carbonic acid
It then dissociates into hydrogen ions and bicarbonate

42
Q

What is the haldane effect?

A

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

43
Q

What part of the brainstem is the major rhythym generator?

A

Medulla oblongata

44
Q

Which network of neurones displays pacemaker activity?

A

Pre-botzinger complex

45
Q

Which neurones are excited which give rise to active inspiration?

A

Dorsal respiratory group neurones

46
Q

Which neurones are excited which give rise to active expiration?

A

Ventral respiratory group neurones

47
Q

What terminates inspiration upon stimulation?

A

Pneumotaxic Centre (PC)

48
Q

Which neurones in the pons stimulate the pneumotaxic centre?

A

Dorsal respiratory group neurones

49
Q

Apneusis

A

Prolonged inspiratory gaps with short expiration (when there is no PC)

50
Q

Apneustic centre

A

Impulses from these neurones excite inspiratory area of medulla

51
Q

Areas respiratory centres receive stimuli from? (7)

A 
Higher brain centres
Stretch receptors
Juxtapulmonary receptors
Joint receptors
Baroreceptors
Central chemoreceptors
Peripheral chemoreceptors
52
Q

Higher brain centres that influence respiratory centres

A

Cerebral cortex
Limbic system
Hypothalamus

53
Q

Stretch receptors

A

In the walls of bronchi and bronchioles

Hering-breuer reflex guards against hyperinflation

54
Q

Juxtapulmonary receptors

A

Stimulated by pulmonary capillary congestion and pulmonary oedema (caused by e.g.left heart failure)
Or pulmonary emboli if capillaries are blocked
Rapid shallow breathing

55
Q

Joint receptors

A

Stimulated by joint movement

56
Q

Baroreceptors

A

Increased ventilatory rate in response to decreased blood pressure

57
Q

Examples of involuntary modification of breathing (4)

A

Pulmonary stretch receptors hering-breuer reflex
Joint receptors reflex in exercise
Stimulation of respiratory centre by temperature, adrenaline or impulses from cerebral cortex
Cough reflex

58
Q

Cough Reflex

A

Short intake of breath
Closure of larynx
Contraction of abdominal muscles increases intra-alveolar pressure
Opening of larynx and expulsion of air at high speed

59
Q

Peripheral chemoreceptors

A

Sense tension of oxygen and carbon dioxide

Sense [H+] in blood

60
Q

Central Chemoreceptors

A

Respond to [H+] in CSF

61
Q

Blood-brain barrier

A

Separates CSF from blood
Relatively impermeable to [H+] and HCO3-
CO2 diffuses across readily

62
Q

Hypercapnia

A

Carbon dioxide retention so can’t hold breath for a long time

63
Q

What causes hypoxia at high altitudes?

A

Decrease partial pressure of inspired oxygen (PiO2)

64
Q

Chronic adaptations to high altitudes hypoxia

A 
Increased RBC production (polycythaemia)
2,3 BPG produced within RBC
Increased number of capillaries
Increased number of mitochondria 
Kidneys conserve acid
65
Q

Increased RBC production leads to…

A

O2 carrying capacity increases

66
Q

2,3 BPG produced within RBC leads to…

A

O2 offloaded more easily into tissues

67
Q

Increased number of capillaries means that…

A

Blood diffuses more easily

68
Q

Increased number of mitochondria means that…

A

O2 can be used more efficiently

69
Q

Kidneys conserving acid leads to…

A

Decrease in arterial pH

Respiratory (19 decks)

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