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Respiratory System > Physiology > Flashcards

Physiology Flashcards

1
Q

Internal respiration is….

External respiration….

A

Internal- The intracellular mechanisms which consumes O2 and produces CO2.
External- the sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of the body

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2
Q

What are the four steps of external respiration?

A

1) Ventilation- The mechanical process of moving gas in and out of the lungs
2) Gas exchange between alveoli and blood- The exchange of O2 and CO2 between the air in the alveoli and the blood in the pulmonary capillaries
3) Gas transport in the blood- The binding and transport of of O2 and CO2 in the circulating blood
4) Gas exchange at the tissue level- The exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells

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3
Q

Explain normal inspiration

A
  • Inspiration is an active process brought about by contraction of inspiratory muscles (rib muscles and diaphragm contracts and moves down)
  • The chest wall and lungs are stretched
  • The increase in the size of the lungs make the intra-alveolar pressure fall
  • This is because air molecules become contained in a larger volume (Boyle’s Law)
  • The air then enters the lungs down its pressure gradient until the intra-alveolar pressure become equal to atmospheric pressure
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4
Q

Explain normal expiration

A
  • Normal expiration is a passive process brought about by relaxation of inspiratory muscles (diaphragm moves up and relaxes and rib muscles also relax)
  • The chest wall and stretched lungs recoil to their pre-inspiratory size because of their elastic properties
  • The recoil of the lungs causes the intra-alveolar pressure to rise
  • This is because air molecules become contained in a smaller volume (Boyle’s Law)
  • The air then leaves the lungs down its pressure gradient until the intra-alveolar pressure become equal to atmospheric pressure
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5
Q

What are the two forces holding the thoracic walls and lungs in close opposition?

A

1) The intrapleural fluid cohesiveness: The water molecules in the intrapleural fluid are attracted to each other.
2) The negative intrapleural pressure: the sub-atmospheric intrapleural pressure create a transmural pressure gradient across the lung wall and across the chest wall. So, the lungs are forced to expand outwards while the chest is forced to squeeze inwards.

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6
Q

What are 3 pressures important in ventilation?

A

1) Atmospheric Pressure
2) Intra-alveolar (intrapulmonary) Pressure
3) Intrapleural (intrathoracic) Pressure

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7
Q

What is a pneumothorax and why does it cause a problem?

A
  • Pneumothorax = air in the pleural space

* This can abolish transmural pressure gradient leading to lung collapse

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8
Q

Explain how the lungs recoil

A

Elastic connective tissue allows the whole structure to bounce back into place and alveolar surface tension produces a force which resists the stretching of the lungs.

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9
Q

Explain the role and importance of pulmonary surfactant

A
  • It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli
  • Surfactant lowers the surface tension of smaller alveoli more than that of large alveoli
  • This prevent the smaller alveoli from collapsing and emptying their air contents into the larger alveoli
  • LaPlace’s law describes the relationship between surface tension, the radius of the bubble and the inwards directed collapsing pressure.
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10
Q

What is 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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11
Q

Define tidal volume

A

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

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12
Q

Define inspiratory reserve volume

A

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

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13
Q

Define expiratory reserve volume

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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14
Q

Define residual volume

A

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

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15
Q

Define inspiratory capacity

A

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

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16
Q

Define functional residual capacity

A

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

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17
Q

Define vital capacity

A

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

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18
Q

Define total lung capacity

A

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

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19
Q

What is the capacity used most in a clinical context?

A

Vital capacity

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20
Q

What is FVC, FEV1 and the FEV1/FVC ratio?

A
  • FVC = Forced Vital Capacity (maximum volume that can be forcibly expelled from the lungs following a maximum inspiration)
  • FEV1 = Forced Expiratory volume in one second.
  • FEV1/FVC ratio. The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) X 100% - Normally more than 70%
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21
Q

What would is the likely cause of

low to normal FVC
low FEV1
low FEV1/FVC

A

Airway obstruction

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22
Q

What is the likely cause of

low FVC
low FEV1
Normal FEV1/FVC

A

Lung Restriction

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23
Q

What is the likely cause of

low FVC
low FEV1
low FEV1/FVC

A

A combination of obstruction and restriction

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24
Q

What effect can disease have on airway resistance?

A

Can increase resistance. This usually has a bigger effect on expiration than inspiration.

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25
Q

Define pulmonary compliance

A

A measure of effort that has to go into stretching or distending the lungs. It is the volume change per unit of pressure change across the lungs. The less compliant the lungs are, the more work is required to produce a given degree of inflation

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26
Q

What causes a decrease in pulmonary compliance and what does this mean?

A
  • Pulmonary compliance is decreased by factors such as pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia and absence of surfactant
  • Decreased pulmonary compliance means greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer). This causes shortness of breath especially on exertion
  • Decrease pulmonary compliance may cause a restrictive pattern of lung volumes in spirometry.
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27
Q

When may increased compliance occur?

A

If the elastic recoil of the lungs is lost. Increased compliance occurs in emphysema. Patients have to work harder to get the air out of the lungs – hyperinflation of lungs. Compliance also increases with increasing age.

28
Q

Define pulmonary ventilation

A

The volume of air breathed in and out per minute. Pulmonary Ventilation (L) = tidal volume (L/breath) x Respiratory Rate (breath/min).

29
Q

Define Alveolar ventilation

A

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

(tidal volume – dead space) x respiratory rate

30
Q

What does the transfer of gases between the body and the atmosphere depend on?

A

1) Ventilation: the rate at which gas is passing through the lungs.
2) Perfusion: the rate at which blood is passing through the lungs

31
Q

What happens in areas which perfusion (rate of blood flow) is greater than ventilation (rate of airflow)?

A

1) CO2 increases in the area and O2 decrease in the area
2) Dilatation of local airways and constriction of local blood vessels
3) Airflow increases and blood flow decreases

32
Q

What happens in areas in which ventilation (rate of airflow) is greater than perfusion (rate of blood flow):

A

1) CO2 decreases in the area and O2 increases in the area
2) Constriction of local airways and dilatation of local blood vessels
3) Airflow decrease and blood flow increases

33
Q

What are four factors that influence the rate of gas exchange across alveolar membrane?

A
  1. Partial Pressure Gradient of O2 and CO2
  2. Diffusion Coefficient for O2 and CO2
  3. Surface Area of Alveolar Membrane
  4. Thickness of Alveolar Membrane
34
Q

What is the partial pressure of a gas and how does this effect movement?

A

The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature. Gases move from higher to lower partial pressures (partial pressure gradient). The whole system basically favours the movement of carbon dioxide out of the tissues and oxygen in.

35
Q

What is the diffusion coefficient of a gas?

A

The solubility of gas in membranes.

36
Q

Name seven non-respiratory functions of the respiratory system

A
  • Route for water loss and heat elimination
  • Enhances venous return (Cardiovascular Physiology)
  • Helps maintain normal acid-base balance (Respiratory and Renal Physiology)
  • Enables speech, singing, and other vocalizations
  • Defends against inhaled foreign matter
  • Removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation
  • Nose serves as the organ of smell
37
Q

What is Henry’s Law?

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. Therefore, the O2 amount dissolved in blood is proportional to the partial pressure.

38
Q

What are the two forms oxygen is present in blood in?

A

Bound to haemoglobin (majority) and physically dissolved (minority).

39
Q

What is the primary factor that determines the percentage saturation of haemoglobin with O2?

A

Partial pressure of oxygen

40
Q

The O2 delivery index to tissues is…

A

a function of cardiac output and the O2 content of arterial blood

41
Q

What can oxygen delivery to tissues be impaired by?

A

• Decreased partial pressure of inspired oxygen
• Respiratory disease
(Both these can decrease arterial PO2 and hence decrease Hb saturation with O2 and O2 content of the blood)

  • Anaemia (This decreases Hb concentration and hence decreases O2 content of the blood)
  • Heart failure (This decreases cardiac output)
42
Q

Describe the cooperativity of haemoglobin?

A
  • The binding of oxygen to one subunit increases the affinity of the binding of oxygen to the remaining subunits.
  • Equally the release of oxygen from one subunit decreases the affinity of remaining subunits.
43
Q

What are the shapes of dissociation curves for haemoglobin and myoglobin? Why are they different?

A 
Haemoglobin= sigmoidal
Myoglobin= hyperbolic

Haemoglobin shows cooperativity, Myoglobin does not, myoglobin has one harm group, haemoglobin has 4.

44
Q

What are the benefits to the haemoglobin curve being sigmoidal?

A

1) Flat upper portions means that moderate fall in alveolar PO2 will not much affect oxygen loading
2) Steep lower part means that the peripheral tissues get a lot of oxygen for a small drop in capillary PO2

45
Q

What does the Bohr effect explain?

A

The curve can be shifted to the right to decrease the affinity of oxygen for haemoglobin. Conditions that cause this are increased PCO2, decreased pH, increased temperature and increased 2,3-biphosphoglycerate. This will happen in working tissues where you want oxygen to be readily offloaded.

46
Q

Explain how and why foetal haemoglobin differs from adult haemoglobin

A
  • Foetal haemoglobin (HbF) differs from adult haemoglobin in structure - HbF has 2 alpha and 2 gamma subunits
  • HbF interact less with 2,3- Biphosphoglycerate in red blood cells
  • Hence, HbF has a higher affinity for O2 compared to adult haemoglobin (HbA)
  • This means O2-Hb dissociation curve for HbF is shifted to the left compared to HbA
  • This would allow O2 to transfer from mother to foetus even if the PO2 is low
47
Q

What does the presence of myoglobin in the blood indicate?

A

Muscle damage

48
Q

What are the three way carbon dioxide is transported in the blood as?

A

Solution (10%)
Bicarbonate (60%)
Carbamino Compounds (30%)

49
Q

What is the haldane effect?

A

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

50
Q

Explain the release of carbon dioxide into the lungs

A
  • At the lungs the Hb pick-up the O2

* This weaken its ability to bind CO2 and H+

51
Q

What is the major breathing rhythm generator?

A

The medulla

52
Q

Name the network of neurons that are believed to generate breathing rhythm

A

Pre-Botzinger complex

53
Q

Explain in terns of neural control what gives rise to inspiration

A
  • Rhythm is generated by Pre-Botzinger complex
  • Excites Dorsal respiratory group neurones (inspiratory)
  • Fire in bursts
  • Firing leads to contraction of inspiratory muscles - inspiration
  • When firing stops there will be passive expiration
54
Q

Explain in terms of neural control what happens during active respiration under hyperventilation

A
  • Increased firing of dorsal neurones will excite a second group called ventral group neurons
  • Excitation results in contraction of internal intercostals, abdominals etc resulting in forceful expiration.
55
Q

What does stimulation of the pneumotaxic centre in the pons cause?

A

Inhibition of inspiration

56
Q

What does stimulation of the apneustic centre in the pons cause?

A

Prolonged inspiration

57
Q

Explain the hering-breur reflex

A
  • Pulmonary stretch receptors are activated during inspiration trigger the reflex
  • The reflex prevents over-inflation of the lungs.
58
Q

Impulses from moving limbs reflexively increases breathing explain factors that may cause this increase

A
  • Adrenaline release
  • Impulses from the cerebral cortex
  • Increase in body temperature
  • Later: accumulation of CO2 and H+ generated by active muscles
59
Q

Explain the cough reflex

A
  • Activated by irritation of airways or tight airways e.g. asthma
  • Afferent discharge stimulates short intake of breath, followed by closure of the larynx, then contraction of abdominal muscles (increases intra-alveolar pressure), and finally opening of the larynx and expulsion of air at a high speed
60
Q

Central chemoreceptors are involved in maintaining ?

A

pCO2 through detection of H+ concentration of the cerebral spinal fluid. This system is very responsive

61
Q

Explain detection of hypoxia by chemical receptors and the sensitivity and importance of this

A

via the peripheral chemoreceptors
• Stimulation occurs only when arterial PO2 falls to low levels (<8.0 kPa)
• Is not important in normal respiration
• This links to the protective mechanism of the flat upper portion of the oxygen haemoglobin dissociation curve which means that there can be a reasonable drop in PO2 but very little drop in SATS.

62
Q

Explain chronic adaptions to high altitude and decreased pressure

A
  • Increased RBC production (polycythaemia) so O2 carrying capacity of blood increases
  • Increased 2,3 Biphosphoglycerate produced within RBC so O2 offloaded more easily into tissues
  • Increased number of capillaries so blood diffuses more easily
  • Increased number of mitochondria so O2 can be used more efficiently
  • Kidneys conserve acid so arterial pH decreases.
63
Q

Alveolar dead space refers to?

A

Alveoli that are well ventilated but not adequately perfused

64
Q

Anatomical dead space refers to?

A

Parts of the bronchial tree not available for airway exchange.

65
Q

The factor that most increases pulmonary ventilation is?

A

Tidal volume

66
Q

Daltons law?

A

The total pressure of a mixture of gases equals the sum of the partial pressures of each component gas

67
Q

Where do you auscultate the lung bases

A

T11

Respiratory System (16 decks)

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