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Human Systems > Respiration- gas transport and control of respiration > Flashcards

Respiration- gas transport and control of respiration Flashcards

1
Q

What adaptations does the respiratory and circulatory system have to facilitate diffusion

A

1) Large surface area for gas exchange.​

2) Large partial pressure gradients.​

3) Gases with advantageous diffusion properties. ​

4) Specialised mechanisms for transporting O2 and CO2 between lungs and tissues.

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2
Q

What is partial pressure

A

Sum of the partial pressures (mmHg) or tensions (torr) of a gas must be equal to total pressure

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3
Q

How is O2 carried in blood

A

-Dissolved
-Bound to haemoglobin

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4
Q

For each mmHg of PO2 how many ml of blood is there

A

0.003ml O2/ 100ml blood

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5
Q

How much O2 does arterial blood contain

A

Arterial blood (PaO2) = 100 mmHg: ​

contains 0.3 ml O2/100ml blood (3ml O2/litre of blood)

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6
Q

What is the structure of haemoglobin

A

Four haem (iron porphyrin compounds) groups joined to globin protein ​

(two α chains and two β​

chains polypeptide chains

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7
Q

How many Hb molecules is there per red blood cell

A

280 million

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8
Q

Is O2 binding to Hb reversible

A

Yes

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9
Q

Explain the Oxyhaemoglobin dissociation curve

A

flat portion: drop in PO2 from 100 to 60 mmHg has minimal effect on Hb saturation.​

Steep portion: large amount​
of O2 is released from Hb with only a small change in PO2, facilitating release into tissues

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10
Q

How many O2 atoms can each Hb bind

A

4

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11
Q

What is O2 saturation

A

Refers to the amount of O2 bound to Hb relative to maximal amount that can bind

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12
Q

How many grams of Hb does normal blood have

A

150g/1L of blood

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13
Q

What is the Hb O2 capacity of normal blood

A

150 x 1.39 = 208 ml O2 / 1L of blood​

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14
Q

What is the overall O2 capacity of normal blood

A

Hb - 208ml / 1L

Dissolved - 3ml / 1L

=211mls / 1L

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15
Q

How can we measure O2 saturation

A

Pulse oximeters used in clinic to measure O2 saturation

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16
Q

How do pulse oximeters work

A

Measures ratio of absorption of red and infrared light by oxyHb and deoxyHb

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17
Q

How much CO2 does a healthy person produce

A

200 ml CO2 / min produced ​

  • 80 molecules CO2 expired by lung for every 100 molecules of O2 entering
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18
Q

What is the respiratory exchange ratio

A

Ratio of expired CO2 to O2 uptake

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19
Q

How is CO2 carried

A

CO2 carried in blood in three forms:

1) 7% dissolved

2) 23% bound to ​haemoglobin (Hb)

3) 70% converted to​ bicarbonate

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20
Q

What is the respiratory exchange ratio in normal conditions

A

0.8 (80 CO2 to 100 O2)

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21
Q

What occurs when PPO2 drops below 60mmHg

A

Fast dissociation of O2 from Hb into blood to allow fast delivery to tissues and cells

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22
Q

What does the CO2 to HCO3- pathway help regulate

A

The CO2 to HCO3- pathway plays a critical role in regulation of H+ ions and in maintaining acid- base balance in body

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23
Q

What factors affect PO2 in blood

A

pH of blood
Body temp

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24
Q

What is the Henderson Hasselbach equation

A

[HCO3]
pH - pK + log ————
Pco2 * sol

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25
Q

How can acidity be regulated in respiration experiments

A

Using ventilation to adjust the PCO2​

By using the kidneys to regulate the bicarbonate concentration.​

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26
Q

What is the main transport system for CO2 in the blood

A

Red blood cells in the form HCO3-

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27
Q

What indicates a healthy lung volume

A

70% of lung volume expired in 1 second

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28
Q

What would be expected in the lung volume of patients with obstructive lung disease e.g. emphysema and asthma etc

A

FEV1/FVC ratio<70% - less than 70% of lung volume expired in 1 second

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29
Q

What does FEV/FVC stand for

A

Forced expiratory volume against
Forced Vital capacity

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30
Q

What does FEC/FVC measure

A

How much air can be forced out of the lung over a specific period

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31
Q

Why do patients with restrictive lung diseases e.g. pulmonary fibrosis, neuromuscular diseases etc have a FEV/FVC ratio of > 70%

A

Their Forced Vital capacity is considerably smaller

Usually 80% or less of healthy individual

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32
Q

How is breathing modulated

A

-singing
-crying
-coughing
-hold breath
-sleep
-exercise

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33
Q

What factors can affect breathing

A

Sleep
Phonation
Emotion
Cardiovascular
Temp
Exercise
Mechanoreception
Chemoreceptors

34
Q

What role do chemoreceptors play in breathing + control

A

Chemoreceptors: provide feedback on blood PO2, PCO2 and pH
Send signals to the brain

35
Q

What do Mechanoreceptors do

A

Provide feedback on mechanical status of lungs, chest wall and airways

36
Q

What does the brain send neural signals to

A
  • Respiratory muscles to produce rhythmic breathing movements, e.g., diaphragm and intercostals​
  • Upper airway muscles, e.g., laryngeal, pharyngeal and tongue.​
  • Produce reflexes to keep airways patent, e.g., cough, sneeze, gag.​
37
Q

What are chemoreceptors

A

Sensory receptors that detect chemical changes in the surrounding environment

In resp system: PO2, PCO2 and pH in blood

38
Q

Where are peripheral chemoreceptors

A

In region of aortic arch and carotid sinuses

39
Q

How do peripheral
chemoreceptors communicate with the brain

A

Information sent via the glossopharyngeal and vagus nerves to the nucleus in brainstem called NTS

40
Q

What is the NTS

A

Nucleus Tractus Solitarius

41
Q

What do peripheral chemoreceptors respond to

A

Decreases in PO2 (hypoxia)

42
Q

What is hypoxia

A

Decreases in CO2

43
Q

What occurs to restore PO2 levels

A
  • Reduction in arterial PO2 ​
  • Peripheral chemoreceptors stimulated
  • Neural signals sent from carotid and aortic bodies to NTS in brainstem
  • Ventilation increases to restore PO2 levels
44
Q

Where does hypoxic response originate

A

Carotid and aortic bodies

45
Q

How does hypoxia affect breathing

A

Below 60 mmHg there is a progressive hyperventilation

Progressive reductions in inspired oxygen have little effect until about 60 mmHg

46
Q

What are central chemoreceptors

A

Central chemoreceptors​ are clusters of neurones in the brainstem that are activated when PCO2 is increased (hypercapnia) or pH decreased

47
Q

How is an increase in arterial PCO2 restored

A
  • Central chemoreceptors ​(brainstem neurones)​ stimulated
  • Signals processed and​ information passed on to neuronal clusters in brainstem involved in​ generating breathing​
  • Ventilation increases to restore PCO2 levels
48
Q

How is breathing affected by Hypercapnia

A

Very small changes in PCO2 have large effects on ventilation (unlike O2)
Hypercapnic response originates in central chemoreceptors in brainstem

Plays major role in moment to moment control of breathing

49
Q

What is Hypercapnia

A

Increase in PCO2

50
Q

What are mechanoreceptors

A

Sensory receptors that detect changes in pressure, movement and touch

In resp system: Movement of lung and chest wall

51
Q

Where are mechanoreceptors located

A

Receptor location: Airway smooth muscle
Stimulus: Inflation/distension of airways
Reflex: Termination of inspiration

Receptor location: Airway epithelium
Stimulus: Rapid lung inflation or deflation, or oedema
Reflex: Sigh or shortened expiration

52
Q

How do signals from mechanoreceptors reach the NTS

A

Vagus nerve

53
Q

Where does the NTS receive info from

A

Mechanoreceptors and peripheral chemoreceptors

54
Q

Where is the rhythm of breathing generated

A

Bilateral cluster of respiratory neurones in fourth ventricle in brainstem above C1

55
Q

What neurones are activated during expiration

A

Expiratory neurones

56
Q

What neurones are activated by inspiration

A

Inspiratory neurones

57
Q

How do signals from the brain reach the respiratory muscles

A

Rhythmic neural signals sent to spinal cord.​

Phrenic nerve exits spinal cord at ​cervical spinal cord level 3-5

Phrenic nerve innervates diaphragm​

Nerves exiting thoracic spinal cord​
innervate intercostal muscles

58
Q

What section of the brain is respiratory rhythm generated

A

Pons and medulla

59
Q

What respiratory groups within the brain produce the signals for resp muscles

A

Pontine respiratory group
Ventral respiratory group (rhythm generating neurones)
Dorsal respiratory group (NTS)

60
Q

What controls volitional and emotional modulation of breathing

A

Higher centres
-cerebral cortex
-limbic system
-hypothalamus

61
Q

How can the area of motor cortex dedicated to a particular muscle be determined

A

Area of motor cortex dedicated to a particular muscle is proportional to the number of motor neurones innervating the muscle

62
Q

What is the Somatotopic organisation of the primary motor cortex (motor homunculus)​

A

Representation of the body parts along the primary motor cortex, or precentral gyrus

A map of the brain areas dedicated to motor processing for different anatomical divisions of the body

63
Q

What components of the nervous system are involved in control of breathing

A

Neural inputs (chemoreceptors & mechanoreceptors

Higher centre modulation ​
(volitional &​ emotional)​

Pontine respiratory group

Medullary rhythm generating​
neurones & NTS

Neural outputs

Motor neurones controlling respiratory muscles

64
Q

What is the signal pathway from the brainstem to the blood in the control of breathing

A

Cerebral cortex
Respiratory centre, medulla
Spinal chord
Respiratory muscles
Lung and chest wall
Alveolar-capillary barrier
Blood

Chemoreceptors bring signals from changes in PCO2, PO2 and pH to respiratory centre (NTS)

65
Q

What are the two types of dead space

A

Anatomical dead space: volume of gas during each breath that fills the conducting airways

Physiological dead space: Total volume of gas in each breath that does not participate in gas exchange, e.g., alveoli that are perfused but not ventilated

66
Q

What are the two separate blood supplies in the lung

A

​

Pulmonary circulation: brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart
​
Bronchial circulation:​ brings oxygenated​ blood to lung parenchyma

67
Q

What is arterial hypoxemia

A

Arterial PO2 < 80mmHg

68
Q

What is:
Hypoxia
Hypercapnia
Hypocapnia

A

Hypoxia: when insufficient O2 to carry out metabolic functions – when arterial PO2 < 60 mmHg

Hypercapnia: increase in arterial PCO2 > 40 mmHg

Hypocapnia: decrease in arterial PCO2 < 35 mmHg

69
Q

What is an anatomical shunt

A

Mixed venous blood ‘shunted’ directly into arterial blood

Alveolar ventilation same, ​
distribution of blood​ flow changed

(in case of lung – mixed pulmonary artery blood shunted into pulmonary veins)

70
Q

Where does an anatomical shunt occur and what does it cause

A

Most anatomic shunts occur within heart - blood from right atrium or ventricle crosses septum to left atrium or ventricle: right to left shunt

Results in varying degrees of hypoxemia

71
Q

What is hypoxemia

A

Levels of oxygen in the blood are lower then normal

72
Q

What is a physiological shunt

A

Ventilation to lung units is absent in presence of continuing perfusion (venous admixture)

Alveolar ventilation different, distribution of blood flow same ​

73
Q

What is atelectasis

A

Obstruction of ventilation​
due to mucous plugs, airway​
oedema, foreign bodies,​
tumours in airways

74
Q

What is the most frequent cause of arterial hypoxemia in patients with resp disorders

A

V-Q mismatching
Some alveoli V/Q > 1, some V/Q < 1

75
Q

What does COPD stand for

A

Chronic obstructive pulmonary disease

76
Q

What is COPD

A

A condition in which airflow is obstructed

COPD encompasses emphysema and chronic bronchitis

77
Q

What are the symptoms of COPD

A

Chronic cough
Chest tightness
Shortness of breath
Increased mucous production

78
Q

What is the most frequent cause of COPD

A

Long term smoking

79
Q

What defect causes emphysema

A

Structures in alveoli over inflated

Lungs loose elasticity, cannot fully expand and contract

Patients can inhale but exhalation is difficult due to decreased elastic recoil

80
Q

What is chronic bronchitis

A

Inflammation of bronchi causing mucous production and excessive swelling

Shortness of breath with mild exertion

Chest infections more prevalent

81
Q

What is pulmonary fibrosis

A

A type of interstitial lung disease
Scarring and thickening of tissue
Decreased elasticity
Decreased gas exchange

82
Q

What would irregular abnormal air spaces, large areas of scarring and irregular thickening of tissue between the alveoli indicate

A

Pulmonary fibrosis

Human Systems (34 decks)

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