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Z- BDS1,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
How can acidity be regulated in respiration experiments
Using ventilation to adjust the PCO2​ By using the kidneys to regulate the bicarbonate concentration.​
26
What is the main transport system for CO2 in the blood
Red blood cells in the form HCO3-
27
What indicates a healthy lung volume
70% of lung volume expired in 1 second
28
What would be expected in the lung volume of patients with obstructive lung disease e.g. emphysema and asthma etc
FEV1/FVC ratio<70% - less than 70% of lung volume expired in 1 second
29
What does FEV/FVC stand for
Forced expiratory volume against Forced Vital capacity
30
What does FEC/FVC measure
How much air can be forced out of the lung over a specific period
31
Why do patients with restrictive lung diseases e.g. pulmonary fibrosis, neuromuscular diseases etc have a FEV/FVC ratio of > 70%
Their Forced Vital capacity is considerably smaller Usually 80% or less of healthy individual
32
How is breathing modulated
-singing -crying -coughing -hold breath -sleep -exercise
33
What factors can affect breathing
Sleep Phonation Emotion Cardiovascular Temp Exercise Mechanoreception Chemoreceptors
34
What role do chemoreceptors play in breathing + control
Chemoreceptors: provide feedback on blood PO2, PCO2 and pH Send signals to the brain
35
What do Mechanoreceptors do
Provide feedback on mechanical status of lungs, chest wall and airways
36
What does the brain send neural signals to
- 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
What are chemoreceptors
Sensory receptors that detect chemical changes in the surrounding environment In resp system: PO2, PCO2 and pH in blood
38
Where are peripheral chemoreceptors
In region of aortic arch and carotid sinuses
39
How do peripheral chemoreceptors communicate with the brain
Information sent via the glossopharyngeal and vagus nerves to the nucleus in brainstem called NTS
40
What is the NTS
Nucleus Tractus Solitarius
41
What do peripheral chemoreceptors respond to
Decreases in PO2 (hypoxia)
42
What is hypoxia
Decreases in CO2
43
What occurs to restore PO2 levels
- 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
Where does hypoxic response originate
Carotid and aortic bodies
45
How does hypoxia affect breathing
Below 60 mmHg there is a progressive hyperventilation Progressive reductions in inspired oxygen have little effect until about 60 mmHg
46
What are central chemoreceptors
Central chemoreceptors​ are clusters of neurones in the brainstem that are activated when PCO2 is increased (hypercapnia) or pH decreased
47
How is an increase in arterial PCO2 restored
- 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
How is breathing affected by Hypercapnia
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
What is Hypercapnia
Increase in PCO2
50
What are mechanoreceptors
Sensory receptors that detect changes in pressure, movement and touch In resp system: Movement of lung and chest wall
51
Where are mechanoreceptors located
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
How do signals from mechanoreceptors reach the NTS
Vagus nerve
53
Where does the NTS receive info from
Mechanoreceptors and peripheral chemoreceptors
54
Where is the rhythm of breathing generated
Bilateral cluster of respiratory neurones in fourth ventricle in brainstem above C1
55
What neurones are activated during expiration
Expiratory neurones
56
What neurones are activated by inspiration
Inspiratory neurones
57
How do signals from the brain reach the respiratory muscles
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
What section of the brain is respiratory rhythm generated
Pons and medulla
59
What respiratory groups within the brain produce the signals for resp muscles
Pontine respiratory group Ventral respiratory group (rhythm generating neurones) Dorsal respiratory group (NTS)
60
What controls volitional and emotional modulation of breathing
Higher centres -cerebral cortex -limbic system -hypothalamus
61
How can the area of motor cortex dedicated to a particular muscle be determined
Area of motor cortex dedicated to a particular muscle is proportional to the number of motor neurones innervating the muscle
62
What is the Somatotopic organisation of the primary motor cortex (motor homunculus)​
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
What components of the nervous system are involved in control of breathing
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
What is the signal pathway from the brainstem to the blood in the control of breathing
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
What are the two types of dead space
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
What are the two separate blood supplies in the lung
​ 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
What is arterial hypoxemia
Arterial PO2 < 80mmHg
68
What is: Hypoxia Hypercapnia Hypocapnia
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
What is an anatomical shunt
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
Where does an anatomical shunt occur and what does it cause
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
What is hypoxemia
Levels of oxygen in the blood are lower then normal
72
What is a physiological shunt
Ventilation to lung units is absent in presence of continuing perfusion (venous admixture) Alveolar ventilation different, distribution of blood flow same ​
73
What is atelectasis
Obstruction of ventilation​ due to mucous plugs, airway​ oedema, foreign bodies,​ tumours in airways
74
What is the most frequent cause of arterial hypoxemia in patients with resp disorders
V-Q mismatching Some alveoli V/Q > 1, some V/Q < 1
75
What does COPD stand for
Chronic obstructive pulmonary disease
76
What is COPD
A condition in which airflow is obstructed COPD encompasses emphysema and chronic bronchitis
77
What are the symptoms of COPD
Chronic cough Chest tightness Shortness of breath Increased mucous production
78
What is the most frequent cause of COPD
Long term smoking
79
What defect causes emphysema
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
What is chronic bronchitis
Inflammation of bronchi causing mucous production and excessive swelling Shortness of breath with mild exertion Chest infections more prevalent
81
What is pulmonary fibrosis
A type of interstitial lung disease Scarring and thickening of tissue Decreased elasticity Decreased gas exchange
82
What would irregular abnormal air spaces, large areas of scarring and irregular thickening of tissue between the alveoli indicate
Pulmonary fibrosis

Z- BDS1,Human Systems (34 decks)

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