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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
Q

Where is the pontine centre located?

A

in the upper pons

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26
Q

What is the function of the pontine centre?

A

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

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27
Q

Where is the apneustic centre located?

A

lower pons

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28
Q

What is the function of the apeustic centre?

A

increase the depth of respiration by acting on the inspiratory centre

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29
Q

How do afferent pathways deliver nerbous connections?

A

via vagus and glossopharyngeal nerves

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30
Q

What type of signals do efferent pathways deliver?

A

signals that drive inspiration and expiration

31
Q

Where do afferent pathways recieve signals from?

A

according to movement of the thoracic region and lung and also from chemoreceptors

32
Q

How do signals travel in the efferent pathway?

A
  • 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
Q

What are the 10 factors that affect respiratory centres?

A
  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
Q

What are the higher centres? And how do impulses from higher centres affect respiratory centres?

A

cerebral cortex, limbic system, hypothalamus

can inhibit or stimulate respiratory centres directly (take control of breathing by thinking about it)

35
Q

How does the Hering-Breur Reflex work?

A
  • 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
Q

When is the Hering-Breur Reflex most active?

A

during the first year of life or during stenuous exercise

37
Q

Where are “J” receptors found?

A

present in the wall of alveoli in close contact with pulmonary capillaries

38
Q

In what conditions are “J” receptors stiumulated?

A
  • pulmonary oedema
  • congestion
  • pneumonia
  • from endogenous chemicals such as histamine
39
Q

What is the consequence of stimulation of “J” receptors?

A

induces apnoea - temporary suspension of breathing followed by rapid shallow breathing

40
Q

Where are irritant receptors of the lungs located?

A

walls of bronchi and bronchioles

41
Q

What are irritant receptors of the lungs? And what are the simulated by?

A
  • rapidly adapting receptors - powerfully stimulated by inhalation of irritants
  • stimulated by harmful chemicals like ammonia or cigarette smoke
42
Q

What is the result of stimulation of irritant receptors of the lungs?

A

induces rapid shallow breathing, mainly from shortening of expiration and also long deep augmented breaths

43
Q

What is the aim of prorioceptors in the chest wall?

A

reflexes from muscles and joints stablaise ventilation in the face of change mechanical conditions

44
Q

What do proprioceptors measure?

A

velocity of rib movements and situated in the joint

45
Q

What do tendons detect?

A

strength of muscle contraction

46
Q

What do muscle spinles detect?

A

monitors length of fibres both statically and dynamically - length and velocity

47
Q

Function of thermoreceptors in respiration

A
  • cutaneous
  • supply signals to cerebral cortex
  • stimulates respiratory centres - hyperventilation
48
Q

Function of pain receptors in respiration

A
  • supply signals to cerebral cortex
  • stimulayes respiratory centres
  • induces hyperventilation
49
Q

What is the cough reflex?

A

protectuve reflex caused by irritation of parts of the respiratory tract beyond the nose

50
Q

What occurs in the cough reflex?

A
  • 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
Q

Why does the sneezing reflex occur?

A

irritation of nasal mucous membrane

52
Q

What occurs in the sneezing reflex?

A

deep inspiration followed by forceful expiration with opened glottis

53
Q

What is the deglutition reflex?

A

swallowing reflex

54
Q

What is the effect of the cortex on ventilation?

A

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
Q

What is the function of chemoreceptors in ventilation?

A

respond to changes in the chemical constituents of the blood or CSF

56
Q

What can chemoreceptors respond to?

A
  • hypoxia
  • hypercpnia - elevated CO2
  • Increased H+ concentration
57
Q

What two groups are the chemoreceptors classified in to?

A
  • central chemoreceptors
  • peripheral chemoreceptors
58
Q

Where are the central chemoreceptors located?

A

in medulla oblongata close to DRG

59
Q

What are central chemoreceptors sensitive to?

A

An increase in H+ concentration

60
Q

What is the action of central chemoreceptors that results in detection of H+ ?

A
  • 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
Q

Why can a change in CSF have a larger effect on pH than a change in plasma PaCO2?

A

There is less protein in the CSF

62
Q

What are central chemoreceptors sensitive to?

A

Arterial PaCO2

[NOT arterial H+ or PaO_2_)

63
Q

Where are peripheral chemoreceptors located?

A

close in location to baroreceptors

around carotid sinus and aortic arch

64
Q

What are peripheral chemoreceptors? And what are the stimulated by?

A

specialised receptor cells (glomus type I)

stimulated by a decrease in PO2 and an increase in H+

65
Q

What do peripheral chemoreceptors synapse with?

A

with afferent nerves which run to the brainstem, sensory portion of CN X from aortic bodies and CN IX from carotid bodies

66
Q

What peripheral chemoreceptor is more important in respiration?

A

carotid

67
Q

What are both peripheral chemoreceptors primarily stimulated by?

A

a decrease in PO2

68
Q

What is the most important factor in the control of respiration?

A

PCO2

69
Q

What is normal PCO2

A

40mmHg or 5.3 kPa

70
Q

What occurs as a result of increased CO2 and decreased pH of the CSF?

A
  • 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
Q

How large is the impact of peripheral chemoreceptors detecting PO2?

A

Minimal

Must drop beloiw 60mmHg/8kPa from 100mmHg/13.3kPa before PO2 becomes a major stimulus for ventilation

72
Q

In what condition would you rely on PO2 to drive ventilation?

A

COPD

PCO2 is chronically elevated due to poor ventilation

73
Q

How does a decrease in pH affect ventilation?

A

increases ventilation

MD3001 - Respiratory Physiology (8 decks)

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