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Physiology 3001 > Neural Control of Respiration > Flashcards

Neural Control of Respiration Flashcards

1
Q

What is the FRC

A
  • Functional residual capacity

The amount air left at the end of a normal breath

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2
Q

What happens to nerve activity during the respiratory cycle?

A

It increases during inspiration and reaches its peak just before inspiration shuts off, it then then remains at a low level during passive expiration. Activity of neurons increases steadily, aparently as a result of a positive feedback mechanism

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3
Q

Where does the rhythmic pattern of breathing originate?

A

The medulla (and the pons)

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4
Q

Do the respiratory muscles have an intrinsic rhythmicity?

A

No

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5
Q

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

A

The brainstem

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6
Q

What are respiratory centres?

A
  • Diffuse networks which act together ro bring about the respiratory effect.
  • Collect sensory information about the levels of oxygen and CO2 in blood that determines the signal sent to respiratory muscles
  • Stimulation leads to respiratory movements which produce alveolar contraction
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7
Q

Where are the respiratory centres located?

A

The medulla oblongata and the pons

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8
Q

What does the inspiratory centre control?

A

Diaphragm and external intercostals

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9
Q

What does the expiratory centre control?

A

Internal intercostals but also partially expiratory neurons .
Inactive during quiet breathing

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10
Q

Where is the inspiratory centre located?

A

Upper part of medulla oblongata (dorsal part)

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11
Q

Where is the expiratory centre located?

A

Medulla oblongata, anterior and lateral to the inspiratory centre

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12
Q

What can the inspiratory centre also be called?

A

The dorsal Respiratory GroupGroup (DRG)

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13
Q

What can the expiratory centre also be called?

A

Ventral Respiratory Group (VRG)

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14
Q

When is the expiratory centre active?

A

During forced expiration or when inspiratory centre is inhibited

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15
Q

Where is the pneumotaxic centre located?

A

The upper pons

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16
Q

What is the function of the pneumotaxic centre?

A

Controls medullary respiratory centres, especially the inspiratory centre through the apneustic centre. It influences inspiratory centre so that duration of inspiration is under control

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17
Q

Where is the apnuestic centre located?

A

The Lower pons

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18
Q

What is the function of the apneustic centre?

A

Increases depth of inspiration by acting on inspiratory centre

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19
Q

What are the afferent connections of the respiratory centre?

A
  • Impulses according to movement of thoracic region and lungs
  • Also from chemoreceptors
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20
Q

What are the efferent connections of the respiratory centre?

A
  • Nerves from the respiratory centre leave in anterior part of the lateral column in spinal cord
  • Terminate in motor neurons in cervical and thoracic segments of spinal cord
  • Supply phrenic nerve that controls diaphragm
  • Supply fibres for intercostal muscles
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21
Q

Where are the impulses coming from in the respiratory centres?

A
  • Higher centres
  • Stretch receptors (Hering-Breur Reflex)
  • J receptors, or pulmonary C-fibres
  • Irritant receptors of lungs
  • Proprioceptors
  • Thermoreceptors
  • Pain receptors
  • Cough reflex
  • Sneezing reflex
  • Deglutition reflex
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22
Q

What areas which are considered ‘higher centres’ contribute towards stimulating or inhibiting the respiratory centre directly?

A
  • Cerebral cortex
  • Limbic system
  • Hypothalamus
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23
Q

Describe the Hering-Breur Reflex?

A
  • Smooth muscle receptors of the upper airways have slowly adapting stretch receptors.
  • When lung is inflated these neurons send impulses to the DRG via the vagus
  • This input is inhibitory limiting inspiration, prevents overinflation of lungs.
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24
Q

When is the Hering-Breur reflex more active?

A
  • In 1st year of life

- During strenous exercise when TV is > 1 L

25
Q

Where are J receptors (or pulmonary C-fibres) present?

A
  • Juxtacapillary receptors present in wall of alveoli, in close contact with pulmonary capillaries
26
Q

What are J receptors (or pulmonary C-fibres) stimulated by?

A
  • Stimulated during conditions like pulmonary oedema, congestion, pneumonia, alsos from endogenous chemicals such as histamine
27
Q

What do ‘J’ receptors induce when stimulated?

A

Apnea - temporary suspension of breathing - followed by rapid shallow breathing

28
Q

What are irritant receptors of the lungs stimulated by?

A
  • Inhalation of irritants

- Harmful chemicals such as amonnia and cigarette smoke

29
Q

Where are irritant receptors of the lung situated?

A

On the walls of bronchi and bronchioles

30
Q

What do the irrritant receptors of the lung induce?

A
  • Rapid shallow breathing, mainly from shortening of expiration
  • But also, long deep augmented breaths, which are taken by mammals every 5-20 mins on average to reverse slow collapse of lungs that occurs during quiet breathing
31
Q

What do proprioceptors do?

A
  • Measure how fast you are breathing and the rate of expansion
  • Aim is for reflexes from muscles and joints to stabilise ventilation in the face of changing mechanical conditions
32
Q

Where are proprioceptors located?

A
  • Receptors in chest wall
  • Situated in joints - measure velocity of rib movement
  • Also found in tendons and muscles
33
Q

What are thermoreceptors?

A
  • Cutaneous
  • Supply signals to cerebral cortex
  • Stimulates respiratory centre
  • Hyperventilation
34
Q

What are pain receptors?

A
  • Supply signals to cerebral cortex,
  • Stimulates respiratory centres
  • Induces hyperventilation
35
Q

What nerve does the cough reflex stimulate?

A

Vagus

36
Q

Describe the cough reflex

A
  • Protective reflex caused by irritation of parts of respiratory tract beyond nose, eg larynx, trachea and bronchi
  • Deep inspiration followed by forceful expiration with closed glottis
  • Glottis opens and explosive outflow or air at high velocity
37
Q

Describe the sneezing reflex

A
  • Irritation of nasal mucous membranes

- Deep inspiration followed by forceful expiration with opened glottis

38
Q

Describe the deglutition reflex?

A
  • Respiration arrested during swallowing of food

- Swallowing apnea or deglutition apnea

39
Q

What can chemoreceptors change in response to?

A
  • Hypoxia
  • Hypercapnea - elevated CO2 in blood
  • Increased H+ concentration (decreased pH)
40
Q

What are the two main groups of chemoreceptors?

A
  • Central chemoreceptors

- Peripheral chemoreceptors

41
Q

What is a better buffer plasma or CSF?

A

Blood plasma

42
Q

How is an increase in H+ concentration detected by the medulla oblongata?

A
  • H+ cannot cross the BBB or CSF barrier
  • CO2 can cross into CSF, and forms carbonic acid, which is unstable and rapidly dissociates to H+ and bicarbonate
  • H+ then stimulates central chemoreceptors
43
Q

Why a rise in PaCO2 cause a larger effect on pH in the CSF than the blood?

A

There is less protein in the CSF than the blood

44
Q

What are the central chemoreceptors sensitive to?

A
  • Arterial PaCO2

Not arterial H+ or PaO2

45
Q

Where are central chemoreceptors located?

A

Medulla oblongata close to DRG

46
Q

What type of cells are peripheral chemoreceptors?

A
  • Specialised receptor cells (glomus type 1) that are stimulated primarily by a decrease in PO2 and an increase in H+ (the latter occuring as a result of increased CO2)
47
Q

What nerve do the sensory fibres of the aortic bodies follow?

A

CN X - Vagus

48
Q

What nerve do the sensory fibres of the carotid bodies follow?

A

CN IX - glossopharyngeal

49
Q

What are the peripheral chemoreceptors stimulated by?

A

A decrease in PO2

50
Q

Where are the peripheral chemoreceptors situated?

A

Around carotid sinus and aortic arch

51
Q

What peripheral chemoreceptors have the greatest effect on respiration?

A

Carotid bodies

52
Q

What are the peripheral chemoreceptors sensitive to?

A
  • PaO2
  • PaCO2
  • pH
  • Blood flow
  • Temperature
53
Q

How much more sensitive are central chemoreceptors to PaCO2 compared with peripheral chemoreceptors ?

A

10 times

54
Q

How do Oxygen levels relate to chemical changes within glomus cells in chemoreceptors?

A
  • When PO2 is high, the K+ channel is open, and the glomus cell is quiescent
  • When PO2 falls, and the K+ channel closes. Vm depolarises
  • Ca2+ channels open
  • Ca2+ influx triggers NT release
  • Sensory afferents signal to the CNS
55
Q

What is normal PCO2?

A

40 mmHg or 5.3 kPa

56
Q

How is ventilation depressed when CO2 is decreased?

A
  • If PCO2 falls the firing rate also falls so there is a corresponding decrease in excitatory input to DRG, with the result of respiration being inhibited
57
Q

What must PO2 drop below before PO2 becomes a major stimulus for ventilation?

A

Must drop below 60 mmHg or 8 kPa from around 100 mmHg (13.3kPa)

58
Q

Why is not recommended to put a patient with COPD on 100% oxygen?

A
  • Patient’s chemoreceptors become insensitive to PCO2 or have become adjusted to lower than normal O2 and higher CO2
  • Patient relies on deline in PO2 to stimulate breathing - HYPOXIC DRIVE
  • Risk is that on 100% oxygen patient will cease breathing, because firing rate of peripheral chemoreceptors will fall and depress ventilatory drive
59
Q

What neuromuscular disorders affect the respiratory system?

A
  • CNS
  • Hemispheric strokes
  • Poliomyelits
  • Diptheria
  • Botulism
  • DMD

Physiology 3001 (20 decks)

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