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MD3001 - Respiratory Physiology > Neural Control of Respiration > Flashcards

Neural Control of Respiration Flashcards

1
Q

What is respiration?

A

An automatic, rhythmic process adapted to meet changing requirements

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2
Q

What must occur for us to inspire?

A

contract the diaphragm and intercostal muscles

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3
Q

What nerves supply the diaphragm and intercostal muscles?

A

phrenic and intercostal nerves

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4
Q

What occurs when we breath out?

A

muscles used to inspire relax

Cease in discharge of action potentials and the chest recoils back to FRC

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5
Q

What does FRC stand for?

A

Functional Residual Capacity

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6
Q

What is the Functional Residual Capacity?

A

The volume left in the lungs at the end of normal expiration

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7
Q

What does the FRC act against?

A

Acts as a buffer against extreme changes in alveolar gas levels in each breath

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8
Q

Draw 2 diagrams showing the changes in tidal volume during inspiration and ecpiration and the number of active inspiratory neurons during the same processes

A
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9
Q

Do the respiratory muscles have intrinsci rhythmicity?

A

NO - not like the heart

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10
Q

What contains all the components to generate the rhythmic pattern of respiration?

A

brainstem

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11
Q

Where is the respiratory rhythm generated?

A

Medulla

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12
Q

How can you alter the pattern of breathing?

A

stimulating various areas of the brainstem

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13
Q

What are respiratory centres?

A

they are diffuse networks, possibly at higher desnity which are active together to bring about the respiratory effect

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14
Q

Where are respiratory centres located?

A

medulla oblongata and pons

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15
Q

What information do the respiratory centres collected?

A

collect sensory information about the level of oxygen and carbon dioxide in the blood and this determines the signal that is sent to respiratory muscles

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16
Q

What is the result of stimulation of respiratory muscles?

A

provides respiratory movements ehich produce alveolar ventilation

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17
Q

What is the aim of the pattern of breathing?

A

to minimise the amount of work done

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18
Q

What are the four medullary centres?

A
  1. Inspiratory centre
  2. expiratory centre
  3. pontine centre
  4. apneustic centre
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19
Q

Where is the inspiratory centre located and what can it be referred to as?

A

upper part of the medulla oblongata

Dorsal Respiratory Group

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20
Q

What is the function of the inspiratory centre>

A

concerned with inspiration

exclusively inspiratory neurons

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21
Q

Where is the expiratory centre located?

A

situated in the medulla oblongata, anterior and lateral to the inspiratory centre

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22
Q

What is another term for the expiratory centre and what type of neurons is it composed of?

A

ventral respiratory group (VRG)

mixture of inspiratory and expiratory neurons

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23
Q

What is the function of the expiratory centre?

A

centre is inative during quiet breathing and when inspiratory centre is active, but during forced breathing or when the inspiratory centre is inhibited it becomes active

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24
Q

What is another name for the pontine centre?

A

pneumotaxic centre

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25
Where is the pontine centre located?
in the upper pons
26
What is the function of the pontine centre?
controls medullary respiratory centres, especially the inspiratory centre through the apneustic centre. It influences inspiratory centre so that the **duration of inspiration is under control**
27
Where is the apneustic centre located?
lower pons
28
What is the function of the apeustic centre?
increase the depth of respiration by acting on the inspiratory centre
29
How do afferent pathways deliver nerbous connections?
via vagus and glossopharyngeal nerves
30
What type of signals do efferent pathways deliver?
signals that drive inspiration and expiration
31
Where do afferent pathways recieve signals from?
according to movement of the thoracic region and lung and also from chemoreceptors
32
How do signals travel in the efferent pathway?
* nerves from respiratory centre leave the brain in anterior part of the lateral column of the spinal cord * terminate in motor neurons in cervical and thoracic segments of the spinal cord * supply phrenic nerve - controls diaphragm * supply fibres from intercostal muscles
33
What are the 10 factors that affect respiratory centres?
1. impulses from higher centres 2. stretch receptors of lung slowly adapting pulmonary receptors 3. "J" receptors or Pulmonary C fibres 4. Irritant receptors of lungs 5. Proprioceptors - receptors in chest wall 6. Thermoreceptors 7. Pain receptors 8. cough reflex 9. sneezing reflex 10. deglutition reflex
34
What are the higher centres? And how do impulses from higher centres affect respiratory centres?
cerebral cortex, limbic system, hypothalamus can inhibit or stimulate respiratory centres directly (take control of breathing by thinking about it)
35
How does the Hering-Breur Reflex work?
* smooth muscle of upper airways has slowly adapting stretch receptors * When lung is inflated these neurons send imoulses to DRG via vagus nerve * input is inhibitory, limiting inspiration --\> orevent over inflation of lungs
36
When is the Hering-Breur Reflex most active?
during the first year of life or during stenuous exercise
37
Where are "J" receptors found?
present in the wall of alveoli in close contact with pulmonary capillaries
38
In what conditions are "J" receptors stiumulated?
* pulmonary oedema * congestion * pneumonia * from endogenous chemicals such as histamine
39
What is the consequence of stimulation of "J" receptors?
induces apnoea - temporary suspension of breathing followed by rapid shallow breathing
40
Where are irritant receptors of the lungs located?
walls of bronchi and bronchioles
41
What are irritant receptors of the lungs? And what are the simulated by?
* rapidly adapting receptors - powerfully stimulated by inhalation of irritants * stimulated by harmful chemicals like ammonia or cigarette smoke
42
What is the result of stimulation of irritant receptors of the lungs?
induces rapid shallow breathing, mainly from shortening of expiration and also long deep augmented breaths
43
What is the aim of prorioceptors in the chest wall?
reflexes from muscles and joints stablaise ventilation in the face of change mechanical conditions
44
What do proprioceptors measure?
velocity of rib movements and situated in the joint
45
What do tendons detect?
strength of muscle contraction
46
What do muscle spinles detect?
monitors length of fibres both statically and dynamically - length and velocity
47
Function of thermoreceptors in respiration
* cutaneous * supply signals to cerebral cortex * stimulates respiratory centres - hyperventilation
48
Function of pain receptors in respiration
* supply signals to cerebral cortex * stimulayes respiratory centres * induces hyperventilation
49
What is the cough reflex?
protectuve reflex caused by irritation of parts of the respiratory tract beyond the nose
50
What occurs in the cough reflex?
* vagus nerve stimulated and cough induced * deep inspiration followed by forceful expiration with closed glottis * glottis opens and expolosive outflow or air at high velocity
51
Why does the sneezing reflex occur?
irritation of nasal mucous membrane
52
What occurs in the sneezing reflex?
deep inspiration followed by forceful expiration with opened glottis
53
What is the deglutition reflex?
swallowing reflex
54
What is the effect of the cortex on ventilation?
you can by-pass the medulla and conciously decide to hold you breath and alter ventilation rates. During this period signals come from the cerebral cortex to the respiratory centres in the medulla but there is also a direct pathway from the cortex to lower motor neurons
55
What is the function of chemoreceptors in ventilation?
respond to changes in the chemical constituents of the blood or CSF
56
What can chemoreceptors respond to?
* hypoxia * hypercpnia - elevated CO2 * Increased H+ concentration
57
What two groups are the chemoreceptors classified in to?
* central chemoreceptors * peripheral chemoreceptors
58
Where are the central chemoreceptors located?
in medulla oblongata close to DRG
59
What are central chemoreceptors sensitive to?
An increase in H+ concentration
60
What is the action of central chemoreceptors that results in detection of H+ ?
* H+ cannot cross the BBB or CSF barrier * CO2 can cross into CSF, and forms carbonic acid, which is unstable and rapidly dissociates into bicarbonate and H+ * The H+ then stimulates central chemoreceptors
61
Why can a change in CSF have a larger effect on pH than a change in plasma PaCO2?
There is less protein in the CSF
62
What are central chemoreceptors sensitive to?
Arterial PaCO2 [NOT arterial H+ or PaO_2_)
63
Where are peripheral chemoreceptors located?
close in location to baroreceptors around carotid sinus and aortic arch
64
What are peripheral chemoreceptors? And what are the stimulated by?
specialised receptor cells (glomus type I) stimulated by a decrease in PO2 and an increase in H+
65
What do peripheral chemoreceptors synapse with?
with afferent nerves which run to the brainstem, sensory portion of CN X from aortic bodies and CN IX from carotid bodies
66
What peripheral chemoreceptor is more important in respiration?
carotid
67
What are both peripheral chemoreceptors primarily stimulated by?
a decrease in PO2
68
What is the most important factor in the control of respiration?
PCO2
69
What is normal PCO2
40mmHg or 5.3 kPa
70
What occurs as a result of increased CO2 and decreased pH of the CSF?
* excitatory input to DRG increasing ventilation to blow off CO2, reducing arterial CO2 * PCO2 returns to normal, pH returns to normal and stimulus for respiration is reduced
71
How large is the impact of peripheral chemoreceptors detecting PO2?
Minimal Must drop beloiw 60mmHg/8kPa from 100mmHg/13.3kPa before PO2 becomes a major stimulus for ventilation
72
In what condition would you rely on PO2 to drive ventilation?
COPD PCO2 is chronically elevated due to poor ventilation
73
How does a decrease in pH affect ventilation?
increases ventilation

MD3001 - Respiratory Physiology (8 decks)

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