Initiation of Breathing

Question 1

Neurogenic initiation

What 2 things did Thomas Lumsden (1923) discover?

think:

• respiratory centres
• medulla and pons

Answer 1

• Discovered that 3 CNS respiratory centres were involved
• The medulla is of primary importance in breathing and Pons smooths out breathing

Question 2

The respiratory centre

what type of groups send impulses to respiratory muscles

Answer 2

• bi-lateral groups

Question 3

the respiratory centre

what do the Dorsal and ventral respiratory groups do?

Answer 3

medullary rhythmicity (initiation of breathing)

Question 4

the respiratory centre

what type of nuclei does the dorsal respiratory group have and where is it found anatomically in the medulla

Answer 4

• has inspiratory nuclei
• found in the dorsal (posterior) section of medulla

Question 5

the respiratory centre

what type of nuclei do the ventral respiratory groups have and where are they found anatomically

Answer 5

has inspiratory and expiratory groups

• VRGs are found bilaterally and ventrally (anterior) in the medulla

Question 6

where are the pneumotaxic and apneustic centres found and state which one is inhibitory and which one is excitatory?

Answer 6

Pneumotaxic centre:
- upper pons
- inhibitory (limits depth of inspirtation which increases rate of breathing)

apneustic centre:
- lower pons
- excitatory

Question 7

THe repiratory centre

what is the main function of:

• Pneumotaxic centre
• Apneustic center

Answer 7

Pneumotaxic centre:
- control rate and depth of breathing (limits inspiration)

Apneustic centre:
- modulates (smooths) breathing cycle to stop things like abrupt halts in inspiration and integrates inspiratory cutoff

Question 8

the respiratory centre

where does the pneumotaxic centre feed into

Answer 8

feeds into the DRG

Question 9

DRG

what nucleus is the dorsal respiratory group found in

Answer 9

the Nucleus tractus solitarius

Question 10

DRG

where is the Dorsal respiratory group located anatomically

Answer 10

dorsally (posteriorly) in the medulla

Question 11

Dorsal respiatroy group (DRG) - medulla

what do the nuclei in the nucleus tractus solitarius drive

Answer 11

drives breathing movements and timing

Question 12

DRG

what 4 structures does nucleus tractus solitaris get sensory information from?

Think: 2 types of receptors
2 types of nerve

Answer 12

• Chemoreceptors
• proprioceptors
• vagus nerve
• glossopharyngeal nerve

Question 13

DRG

where does the nucleus tractus solitarius output to?

Answer 13

outputs to inspiratory muscles

Question 14

DRG

outline the nature of the action potentials from the nucleus tractus solitarius to the inspiratory muscles

Answer 14

repetitive “ramped” bursts of inspiratory neuronal action potentials for 2 secs, allowing inspiration, and then 3 seconds off, allowing for expiration

Question 15

Ventral Respiratory Group (VRG)

where is the VRGs compared to:
- the medulla
- DRG

Answer 15

either side of medulla and anterior and lateral to the DRG

Question 16

VRG

which 2 nuclei is the VRG located in

Answer 16

located in:
- nucleus para-ambiguus
- nucleus retroambiguus

Question 17

where does the nucleus para-ambiguus supply?

Answer 17

• Laryngeal muscles
• pharyngeal muscles

Question 18

where does the nucleus retroambiguus supply

Answer 18

diaphragm and external intercostal muscles

Question 19

VRG

what does the VRG contain nuclei for?

Answer 19

both inspiratory and expiratory nuclei

Question 20

VRG

what type of breathing is VRG involved in?

Answer 20

• active inspiration
• active expiration (ie: voluntary forced exhalation)

Question 21

VRG

when in the VRG inactive

Answer 21

inactive in normal quiet breathing

VRG is inactive in normal breathing and only activates in ACTIVE breathing

Question 22

VRG

what places do the nucleus retroambiguus and the nucleus para-ambiguus in the VRG feed into

Answer 22

Nucleus retroambiguus:
- diaphragm and external intercostal muscles

Nucleus Para-ambiguus:
- Laryngeal and pharyngeal muscles

Question 23

Central pattern generation

what are the 3 phases of central pattern generation for breathing

Answer 23

• inspiratory phase
• post inspiratory/expiratory phase 1
• expiratory phase II

Question 24

central pattern generation

what neurotransmitters are associated in central pattern generation in breathing

Answer 24

• NDMA
• GABA

Question 25

# central pattern generation where are neurones with different firing patterns concentrated near in breathing?

Answer 25

concentrated near pre-Botzinger complex

Question 26

# efferent pathway from the respiratory centres what spinal tract come from the respiratory centres in breathing

Answer 26

Bulbospinal Tract

Question 27

# efferent pathways from respiratory centres where does the phrenic nerve originate from?

Answer 27

rootlets formed from cervical spinal nerves C3,C4 and C5 ## Footnote C3, C4, C5 keep the diaphragm alive

Question 28

# efferent pathway where do intercostal nerves exit and where do they provide input to?

Answer 28

- exit thoracic and lumbar spine - provide input to the intercostal and abdominal muscles

Question 29

# efferent pathways what does the phrenic nerve do and where does it originate

Answer 29

- gives motor control to the diaphragm - formed by rootlets coming from cervical spine C3,C4,C5 ## Footnote C3, C4, C5 keep the diaphragm alive

Question 30

# Pneumotaxic centre (upper pons) outline the 3 steps of how pneumotaxic centre stops the lungs becoming too full ## Footnote think: - inhibitory impulses - limiting activity of 2 places - what this leads to

Answer 30

1. Pneumotaxic centre sends continual inhibitory impulses to inspiratory centre in DRG of medulla oblongata 2. this limits activity of phrenic nerve and inhibits apneustic centre 3. this decreases the tidal volume which prevents the lungs becoming too full

Question 31

# Pneumotaxic centre what happens in you stimulate the pneumotaxic centre more vs if you stimulated less

Answer 31

stimulated more: breathe fast and shallow Stimulated less: inspiratory depth increases and slower breaths

Question 32

# apneustic centre what does overstimulation of the apneustic centre do and how?

Answer 32

causes apneusis (gasping) by exciting inspiratory neurones, prolonging inspiration

Question 33

what happens if there is damage to the apneustic centre?

Answer 33

respiratory cycle is abrupt (no smoothness)

Question 34

what 2 things inhibits the apneustic centre?

Answer 34

- Stretch receptors at **(max inspiration)** - Pneumotaxic centre

Question 35

# PNeumotaxic centre what happens if you have upper pons damage

Answer 35

Deep long breaths as pneumotaxic centre is most likely damaged.

Question 36

What 2 nerves is the nucleus tractus solitairus a sensory terminal for and what do these nerves do?

Answer 36

2 nerves: - vagus - glossopharyngeal These nerves transmit sensory signals from different receptors to therespiratory centre

Question 37

outline where the bulbospinal inspiratory neurones start, descend to and where they end

Answer 37

descend: from respiratory centre to the anterolateral column of the spinal cord terminates: in anterior horn of cervical and thoracic vertebral segments.