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Systems Physiology > Control of Ventilation > Flashcards

Control of Ventilation Flashcards

1
Q

What is Dyspnea

A

Sensation of shortness of breath

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2
Q

What do the Pons respiratory centres do

A

Influence and modify activity of the medullary centres to smooth out transitions between inspiration and expiration

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3
Q

What does the Apneustic centre of the pons respiratory centre do

A

Sends signal to the Dorsal Respiratory Group (DRG) in the medulla to delay the inspiratory cut off from the pneumotaxic centre and vagus, it excites the inspiratory centres

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4
Q

What does the Pneumotaxic centre of the pons respiratory centre do

A

Acts as “off switch” neurons for inspiration. Stimulation of this centre terminates inspiration earlier to reduce tidal volume and cause higher respiratory frequency

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5
Q

What is the Dorsal Respiratory Group (DRG) also known as

A

The inspiratory centre

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6
Q

Where is the DRG located

A

Located near the root of the cranial nerve IX (glossopharyngeal) in the dorsomedial medulla (ventrolateral nucleus)

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7
Q

What does the DRG do

A

Excites the inspiratory muscles includes the diaphragm, external intercostals and the Ventral Respiratory Group (VRG) neurons

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8
Q

What inputs does the DRG receive

A

Pretty much all peripheral afferents (chemo., mechanism., proprio.) via the vagus and glossopharyngeal nerves
Apneustic centre

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9
Q

What do the inspiratory neurons of the Ventral Respiratory Group (VRG) activate

A

Accessory muscles of inspiration and external intercostals

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10
Q

What do the expiratory neurons of the Ventral Respiratory Group (VRG) activate

A

Internal intercostals and abdominal muscles

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11
Q

When are the expiratory neurons of the VRG active

A

Only during exercise but not during normal breathing

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12
Q

Where are the DRG and VRG located

A

In the Medulla Oblongata

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13
Q

What factor is the main driving force for breathing

A

PaCO2

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14
Q

Why are chemoreceptors more sensitive to CO2 than O2

A

Oxygen content of the blood decreases more slowly due to the large reservoir of oxygen attached to haemoglobin

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15
Q

What is the role of chemoreceptors

A

They provide the input to modify the rate and depth of breathing to maintain arterial PaCO2 at 40mmHg

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16
Q

What are the 2 kinds of chemoreceptor

A

Central

Peripheral

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17
Q

What are central chemoreceptors responsive to and what do they use to carry out their role

A
  • responsive to increased arterial PaCO2

- Act by way of CSF [H+]

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18
Q

What are peripheral chemoreceptors responsive to

A
  • Decreased arterial PaO2
  • Increased arterial PaCO2
  • Increased [H+]
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19
Q

Where are the central chemoreceptors located

A

0.2mm below the anterolateral surfaces of the medulla, close to the origins of the glossopharyngeal and vagus nerve

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20
Q

If PaCO2 increases what happens to the ventilation

A

It increases

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21
Q

What do the central chemoreceptors respond to

A

pH of the CSF.

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22
Q

How is carbonic acid formed in the CSF

A

CO2 combines with water to form carbonic acid that dissociates to form Hydrogen ions and bicarbonate

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23
Q

What body structure receives more blood flow than any other organ

A

The peripheral chemoreceptors

2000ml/100g/min

24
Q

Despite the very high metabolic rate of the peripheral chemoreceptors, what keeps the capillary PO2 and PCO2 close to arterial values

A

the mad blood flow

25
Q

What type of cell is a carotid body

A

chemoreceptor

26
Q

What are the type 1 and type 2 cells of the carotid body

A

Type 1 = gloms cell

Type 2 = Sustentacular cell

27
Q

What are the features of the glomus cells

A
  • sensitive to local changes in PO2 (mainly), PCO2 and pH

- Lots of neurotransmitter cytoplasmic granules (Dop., NA., ACh.)

28
Q

What are the features of the sustentacular cells

A 
no granules
function = ?
Its an interstitial cel that wraps around glomus and nerve endings in the chemoreceptor
29
Q

Inhibiting why channels leads to depolarisation in the glomus cell

A

K+ channels

30
Q

What are the carotid and aortic bodies of the peripheral chemoreceptors sensitive to

A 
Carotid = PaO2, PaCO2 and pH
Aortic = PaO2, PaCO2 but not pH
31
Q

Afferents of which nerves go to the carotid and aortic bodies of the peripheral chemoreceptors

A 
Carotid = Glossopharyngeal
Aortic = Vagus
32
Q

Which bodies in the peripheral chemoreceptors respond the strongest

A

Carotid > Aortic

33
Q

What structures in the medullary respiratory centres monitor arterial oxygen levels

A

Aortic and carotid bodies

34
Q

What is needed for arterial PaO2 to become a major stimulus for increased ventilation

A

major drop in PaO2 (to 60mmHg)

35
Q

How does PCO2 change as a stimulus if CO2 is not removed (like in emphysema and chronic bronchitis)

A

Chemoreceptors become unresponsive to PCO2

36
Q

If CO2 isn’t removed and chemoreceptors become unresponsive what is then used as a stimulus

A

PaO2

37
Q

If the pH falls does ventilation increase of decrease and what is this response mediated by

A

Ventilation increases and this is mediated by peripheral chemoreceptors

38
Q

What are the 3 types of mechanoreceptors that are in the lungs and airways

A

Slowly adapting
Rapidly adapting
C-Fibre endings

39
Q

What are the 3 mechanoreceptors innervated by

A

The vagus nerve

40
Q

Pulmonary stretch receptors are responsible for which reflex

A

Hering-Breuer Reflex

41
Q

What does stimulation of pulmonary stretch receptors cause when lungs are maximally inflated and when is this response important

A

Inhibits respiration - limiting tidal volume

Important in situations where there is a central drive increasing tidal volume - during exercise

42
Q

What is unique about the firing of sensory signals of slowly adapting mechanoreceptors

A

they continue to fire as long as the stretch is held.

43
Q

How are the pulmonary stretch receptors responsible for Respiratory Sinus Arrhythmia (tachycardia during I relative to E)

A 
Stretch =
Increased afferent vagal discharge -->
Medullary Cardiovascular centre =
Decreased parasympathetic  and increased sympathetic activity =
Increased Heart Rate
44
Q

What are 2 types of unmyelinated free nerve endings involved in the mechanical control of respiration

A

Pulmonary C fibres

Bronchial C fibres

45
Q

Where are Pulmonary C fibres (Juxta alveolar/J receptors) found and what are they sensitive to

A

Within the walls of pulmonary capillaries

Sensitive to products of inflammation (histamine, bradykinin etc)

46
Q

What does the reflex of pulmonary c fibres result in

A

Rapid shallow breathing

47
Q

Where are bronchial C fibres found

A

In the conducting airways

48
Q

What are bronchial c fibres sensitive to

A

Products of inflammation

49
Q

What does the reflex of bronchial c fibres do

A

bronchoconstriction
Increased airway vascular permeability
Hyperpnoea (deep inhalation)
Laryngeal constriction

50
Q

What are irritant receptors

A

Respond to chemical and mechanical irritants

They have myelinated nerve endings

51
Q

Name 2 upper airway irritant receptors

A

Nasal

Pharyngeal + Laryngeal

52
Q

Branches of which afferent nerves are connected to nasal receptors

A

Trigeminal + Olfactory

53
Q

What reflexes are nasal receptors responsible for

A

Sneezing

Diving - water instilled into the nose = apnea laryngeal closure, bronchoconstriction + bradycardia etc

54
Q

Branches of which afferent nerves are connected to pharyngeal + laryngeal receptors

A

Laryngeal + Glossopharyngeal nerves

55
Q

What reflexes are pharyngeal + laryngeal receptors responsible for

A
  • Aspiration/sniff/swallowing reflexes

- Negative pressure induced abduction

56
Q

Mechanoreceptors in the costovertebral joints are sensitive to what

A

Rib displacement

57
Q

Why are the proprioceptors in the costovertebral joints though to be the main site of impulses causing conscious sensation of lung distension

A

The sensation is still present when the vagus is severed and input from the pulmonary and intercostal stretch receptors is lost

Systems Physiology (28 decks)

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