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Physiology Flashcards

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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
Pulmonary compliance
Measure of effort that has to go into stretching or distending the lungs Volume change per unit of pressure change across the lungs
26
Factors which decrease pulmonary compliance (5)
pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant
27
Factors which increase pulmonary compliance
elastic recoil of lungs is lost-emphysema
28
Pulmonary Ventilation
Tidal volume x respiratory rate | The volume of air breathed in and out per minute
29
Alveolar Ventilation
(Tidal volume-dead space volume) x respiratory rate | The volume of air exchanged between the atmosphere and alveoli per minute
30
Ventilation Perfusion Match
Local controls act on the smooth muscles of airways and arterioles to match airflow to blood flow
31
Four factors which influence rate of gas exchange across alveolar membrane
Partial pressure gradient of O2 and CO2 Diffusion coefficient for O2 and CO2 Surface area of alveolar membrane Thickness of alveolar membrane
32
What would a big gradient between PAO2 (alveolar) and PaO2 (arterial) indicate?
Problems with gas exchange in the lungs | Right to left shunt in the heart
33
Non-respiratory functions of respiratory system (7)
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
Oxygen delivery index (DO2l)
Oxygen content of arterial blood(CaO2) x Cardiac index (CI)
35
What determines the oxygen content of arterial blood
The haemoglobin concentration [Hb] and the saturation of Hb with O2 CaO2 = 1.34 x [Hb] x SaO2
36
Factors that affect oxygen delivery to the tissues (4)
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
Function of myoglobin
Provides a short-term storage of O2 for anaerobic conditions | Present in skeletal and cardiac muscles
38
Means of CO2 transport in the blood
Solution (10%) As bicarbonate (60%) As carbamino compounds (30%)
39
What is the effect of partial pressure on gas solubility?
If the partial pressure in the gas phase is increased the concentration of the gas in the liquid phase would increase proportionally
40
How are carbamino compounds formed?
Combination of CO2 with terminal amine groups in blood proteins
41
How is bicarbonate formed in the blood?
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
What is the haldane effect?
Removing O2 from Hb increases the ability of Hb to pick-up CO2 and CO2 generated H+
43
What part of the brainstem is the major rhythym generator?
Medulla oblongata
44
Which network of neurones displays pacemaker activity?
Pre-botzinger complex
45
Which neurones are excited which give rise to active inspiration?
Dorsal respiratory group neurones
46
Which neurones are excited which give rise to active expiration?
Ventral respiratory group neurones
47
What terminates inspiration upon stimulation?
Pneumotaxic Centre (PC)
48
Which neurones in the pons stimulate the pneumotaxic centre?
Dorsal respiratory group neurones
49
Apneusis
Prolonged inspiratory gaps with short expiration (when there is no PC)
50
Apneustic centre
Impulses from these neurones excite inspiratory area of medulla
51
Areas respiratory centres receive stimuli from? (7)
``` Higher brain centres Stretch receptors Juxtapulmonary receptors Joint receptors Baroreceptors Central chemoreceptors Peripheral chemoreceptors ```
52
Higher brain centres that influence respiratory centres
Cerebral cortex Limbic system Hypothalamus
53
Stretch receptors
In the walls of bronchi and bronchioles | Hering-breuer reflex guards against hyperinflation
54
Juxtapulmonary receptors
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
Joint receptors
Stimulated by joint movement
56
Baroreceptors
Increased ventilatory rate in response to decreased blood pressure
57
Examples of involuntary modification of breathing (4)
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
Cough Reflex
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
Peripheral chemoreceptors
Sense tension of oxygen and carbon dioxide | Sense [H+] in blood
60
Central Chemoreceptors
Respond to [H+] in CSF
61
Blood-brain barrier
Separates CSF from blood Relatively impermeable to [H+] and HCO3- CO2 diffuses across readily
62
Hypercapnia
Carbon dioxide retention so can't hold breath for a long time
63
What causes hypoxia at high altitudes?
Decrease partial pressure of inspired oxygen (PiO2)
64
Chronic adaptations to high altitudes hypoxia
``` Increased RBC production (polycythaemia) 2,3 BPG produced within RBC Increased number of capillaries Increased number of mitochondria Kidneys conserve acid ```
65
Increased RBC production leads to...
O2 carrying capacity increases
66
2,3 BPG produced within RBC leads to...
O2 offloaded more easily into tissues
67
Increased number of capillaries means that...
Blood diffuses more easily
68
Increased number of mitochondria means that...
O2 can be used more efficiently
69
Kidneys conserving acid leads to...
Decrease in arterial pH

Respiratory (19 decks)

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