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Respiratory SOH > Physiology > Flashcards

Physiology Flashcards

1
Q

Internal Respiration

A

intracellular process which consumes oxygen and produces carbon dioxide

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2
Q

External Respiration

A

Sequence of events leading to the exchange of oxygen and carbon dioxide between the atmosphere and the cells of the body

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3
Q

4 steps of external respiration

A
  1. Ventilation - Moving gas in and out of the lungs. Gas exchange between atmosphere and alveoli (air sacs).
  2. Gas exchange - between the air in the alveoli and the blood
  3. Gas transport - in the blood
  4. Gas exchange - between the blood and the tissues
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4
Q

Boyle’s Law

A

As the volume of a gas increases, the pressure exerted by the gas decreases.
Inversely proportional
Eg:
Before inspiration - intra-alveolar pressure is equivalent to the atmospheric pressure
During inspiration - Thorax and lungs expand (volume increases) causing the intra-alveolar pressure to become less than the atmospheric pressure (pressure decreases).

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5
Q

Intra-pleural pressure

A

The pressure within the pleural sac. The pressure exerted outside the lungs within the thoracic cavity.
Falls during inspiration.
Rises during expiration.

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6
Q

Linkage of lungs to thorax

A

Negative intra-pleural pressure - the below-atmospheric intra-pleural pressure creates a transmural pressure gradient across the lung wall and chest wall. Causes lungs to expand outwards while chest squeezes inwards.

Intra-pleural fluid cohesiveness - water molecules in intra-pleural fluid are attracted to each other and resist being pulled apart. Pleural membranes therefore stick together.

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7
Q

Inspiratory muscles

A

Diaphragm - major inspiratory muscle. Contraction (flattening) of the diaphragm lowers the diaphragm and thus increases the volume of the thorax vertically, increasing the vertical diameter of the chest.

External Intercostal Muscle - contraction elevates rib cage and causes the sternum to move upwards and outwards. This increases the AP diameter of the chest

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8
Q

Expiratory muscles

A

Diaphragm - Relaxes (moves up to original position).

External Intercostal Muscles - relaxation causes rib cage to get smaller and return to original position

Chest wall and stretched lungs recoil (volume decreases) causing intra-alveolar pressure to rise (pressure increases) as air is now contained in a smaller volume. Air then leaves the lungs until intra-alveolar pressure = atmospheric pressure

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9
Q

Recoiling of lungs during expiration

A

Elastic connective tissue - everything bounces back into place
(If elastic properties are lost, air is trapped in the lungs (hyperinflation) as it can’t be pushed out causing difficulties in expiration).

Alveolar surface tension - attraction of water molecules at liquid air interface which produces a force which resists the stretching of lungs. Makes the lungs recoil or collapse

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10
Q

Pulmonary Surfactant

A

Reduces alveolar surface tension. Smaller alveoli have a higher tendency to collapse and pulmonary surfactant helps to prevent this from happening.
Secreted by type II alveoli and lowers alveolar surface tension by interspersing between the water molecules lining the alveoli.
Premature babies may not have enough and this can result in respiratory distress syndrome

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11
Q

Alveolar Interdependence

A

Helps to keep the alveoli open.
If an alveolus starts to collapse the surrounding alveoli will stretch then recoil which exerts expanding forces on the collapsing alveoli and forces it to open

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12
Q

Inspiration

A

Active process, depends on contraction of inspiratory muscles.

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13
Q

Expiration

A

Passive process, relaxation of inspiratory muscles.

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14
Q

Forces promoting alveoli opening (3)

A

Pulmonary surfactant
Alveolar interdependence
Transmural pressure gradient (negative intra-pleural pressure)

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15
Q

Forces promoting alveolar closure (2)

A

Elastic connective tissue

Alveolar surface tension

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16
Q

Major muscles of inspiration

A

Diaphragm
External Intercostal Muscles
Sternum
Ribcage

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17
Q

Accessory muscles of inspiration

A

Sternocleidomastoid

Scalenus

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18
Q

Muscles of active expiration

A

Internal Intercostal Muscles

Abdominal Muscles

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19
Q

Tidal Volume (TV)

A

Volume of air entering of leaving the lungs in a single breath

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20
Q

Inspiratory Reserve Volume (IRV)

A

Extra volume of air maximally inspired beyond the tidal volume

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21
Q

Inspiratory Capacity (IC)

A

Maximum volume of air inspired after a normal quiet expiration (IC=TV+IRV)

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22
Q

Expiratory Reserve Volume (ERV)

A

Extra volume of air maximally expired beyond the tidal volume

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23
Q

Residual Volume (RV)

A

Volume of air left in the lungs after a maximal expiration

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24
Q

Functional Residual Capacity (FRC)

A

Volume of air remaining in the lungs after a normal passive expiration

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25
Q

Vital Capacity (VC)

A

The maximum volume exhaled after a maximal inspiration. (VC=TV+IRV+ERV)

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26
Q

Total Lung Capacity (TLC)

A

The maximum volume the lungs can hold (TLC=VC+RV)

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27
Q

Forced Vital Capacity (FVC)

A

The maximum volume of air forcibly expelled from the lungs following a maximal inspiration

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28
Q

Forced Expiratory Volume in 1 second (FEV1)

A

The volume of air expelled during the first second of expiration in an FVC determination.

29
Q

FEV1/FVC ratio

A

The proportion of FVC that can be expired in one second.

Useful in diagnosis of obstructive and restrictive lung diseases

30
Q

Obstructive lung disease (FEV1/FVC)

A

FEV1/FVC ratio = low (<70%)
FEV1 = low
FVC = normal/low

31
Q

Restrictive lung diseases (FEV1/FVC)

A

FEV1/FVC ratio = normal (>70%)
FEV1 = low
FVC = low

32
Q

Airway Resistance

A

Primary determinant is the radius of the conducting airway. The smaller the radius, the higher the resistance, the lower the air flow.
ie: as resistance increases, air flow decreases.
As resistance increases, there is an increase in airway pressure upstream which helps open the airways by increasing the driving pressure between the alveolus and airway

33
Q

Dynamic Airway Compression (normal)

A

Rising intra-pleural pressure during expiration compresses the airway and alveoli.
Pressure applied to alveoli - helps push air out of lungs
Pressure applied to airways - compresses airway

34
Q

Dynamic Airway Compression (obstructive)

A

Decreased airway pressure along the airway downstream resulting in airway compression by the rising intra-pleural pressure during active expiration. Airway is more likely to collapse.

35
Q

Peak Flow Meter

A

Assesses airway function - estimates speed at which someone can get air out of lungs.
Useful for obstructive lung diseases

36
Q

Pulmonary Compliance

A

Measure of effort that goes in to stretching or distending the lungs

37
Q

Decreased Pulmonary Compliance

A

More work required to inflate the lungs, lungs are stiffer.
Can cause a restrictive spirometry pattern
eg: pulmonary fibrosis, pulmonary oedema, pneumonia, lung collapse

38
Q

Increased Pulmonary Compliance

A

Where elastic recoil of lung is lost.
Patients work harder to get air out of lungs
eg: emphysema, increasing age

39
Q

Anatomical Dead Space

A

Inspired air which remains in the airways

Not available for gas exchange.

40
Q

Pulmonary Ventilation

A

Volume of air breathed in and out per minute.

PV=RRxTV

41
Q

Alveolar Ventilation

A

Volume of air exchanged between atmosphere and alveoli per minute.
Represents the air available for gas exchange with blood.
AV=(TV-ADS)xRR

42
Q

Ventilation Perfusion (V/Q)

A

Rate at which gas is passing through the lungs (V) vs the rate at which blood is passing through the lungs (Q)

Low V/Q ratio at the bottom of the lungs - decreased ventilation, increased perfusion

High V/Q ratio at the top of the lungs - increased ventilation, decreased perfusion

Can be a slight variation in normal people
Significant difference in disease

43
Q

Alveolar Dead Space

A

Ventilated alveoli which are not adequately perfused.

44
Q

Decreased O2 causes pulmonary arteries to _____ and systemic arteries to _____ (vice versa)

A

Vasoconstrict

Vasodilate

45
Q

Factors influencing the rate of gas exchange across alveolar membrane (4)

A

Partial pressure gradient
Diffusion coeficient
Surface area
Thickness

46
Q

Partial Pressure Gradient

A

Gases move from high to low partial pressure.
Favours the movement of O2 as the partial pressure gradient for CO2 is much smaller.
Most important factor.

47
Q

Diffusion Coefficient

A

Solubility.

CO2 diffuses more readily than O2 as CO2 is 20 times more soluble than O2

48
Q

Surface Area

A

As the surface area increases, the rate of gas exchange also increases

49
Q

Thickness of the membrane

A

The thicker the membrane, the lower the rate of gas exchange.
Inverse proportion

50
Q

Henry’s Law

A

As we increase the partial pressure of a gas, the more gas will dissolve in the liquid

51
Q

O2 transport in the blood (2)

A

Bound to haemoglobin (majority)

In a dissolved form

52
Q

Hb structure

A

2 alpha chains, 2 beta chains
4 haem groups - each haem group reversibly binds one O2 molecule
If all 4 haem groups are bound with O2 then we say the Hb is saturated

53
Q

Saturation

A

Depends on PO2. If the PO2 is normal then the Hb will be saturated.

54
Q

O2 Hb dissociation curve

A

Sigmoidal shaped curve.
Relationship between the PO2 in the blood and the % of Hb saturation with O2 (SpO2).
If one O2 molecule binds to Hb then this increases the affinity of Hb for O2 (co-operativity).

55
Q

Oxygen delivery to tissues

A

Heart - cardiac output delivers blood to the tissues

O2 content of arterial blood - determined by the Hb concentration and the saturation of Hb with O2.

56
Q

Bohr Effect

A

Shifts the O2 Hb sigmoid curve to the right.
Increased release of O2 at tissues in the presence of the following conditions:
- Increased PCO2 - aids delivery of O2 to tissues as this decreases the affinity of Hb for O2
- Increased H+ ions - aids delivery of O2 to tissues as Hb affinity to bind to O2 decreases thus giving the O2 up to the tissues
- Increased temperature

57
Q

Foetal Hb

A

2 alpha chains, 2 gamma chains
Higher affinity for O2 compared to normal adult Hb.
Thus the O2 Hb sigmoid curve shifts to the left.

58
Q

Myoglobin (Mb)

A

Present in skeletal and cardiac muscles.
Produces a hyperbolic curve.
One haem group per Mb molecule thus there is no co-operative binding of O2.
Presence of Mb in the blood represents muscle damage.

59
Q

CO2 transport in the blood (3)

A

As bicarbonate (majority)
Dissolved form
As carbamino compounds

60
Q

CO2 transport in blood - As bicarbonate

A

CO2 diffuses down it’s partial pressure gradient from the tissue into the blood (RBC’s). In RBC’s:
CO2 reacts with H2O in the presence of CA to from H2CO3.
From H2CO3, HCO3- (bicarbonate) and H+ ions are formed. These products are constantly removed from the process to ensure that the reaction continues to proceed.

61
Q

CO2 transport in blood - In dissolved form

A

CO2 is 20 times more soluble than O2.

By Henry’s Law: the higher the partial pressure, the greater the amount of soluble CO2 will be present.

62
Q

CO2 transport in blood - As carbamino compounds

A

Formed by combo of CO2 with terminal amine groups in blood proteins.
Deoxygenated Hb can bind more CO2 than oxygenated Hb

63
Q

Haldane Effect

A

Removing O2 from tissues (Bohr effect) increases the affinity for CO2 to bind to Hb and increases the affinity of CO2 generated H+.

64
Q

CO2 dissociation curve

A

Linear curve.

More CO2 content in the tissues than at arterial blood.

65
Q

What is the major rhythm generator

A

The Medulla Oblongata

66
Q

Pre-Botzinger complex and inspiration

A

Generates the breathing rhythm
This excites dorsal respiratory group neurones (inspiratory)
Contraction of inspiratory muscles
When firing stops, passive expiration occurs

67
Q

Pons respiratory centres

A

Modify the breathing rhythm

  • pneumotaxic centre (terminates inspiration)
  • apneustic centre (prolongs inspiration)
68
Q

Active expiration

A

Ventral respiratory group neurones are excited
This excites muscles of active expiration
Leads to active expiration

69
Q

CO2 and H+ diffusing across BBB

A

CO2 diffuses well

H+ doesn’t diffuse well

Respiratory SOH (25 decks)

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