Functional Neuroanatomy of Brainstem Respiratory Network

Question 1

What are the inputs to the brainstem respiratory network?

Answer 1

Proprioception - exercise
Limbic system
Sleep
Thermoreception
Chemoreception
Mechanoreception - from lung walls

Question 2

What are the outputs from the brainstem respiratory network and what do they control?

Answer 2

Cranial resistance MNs - trachea constriction - valve effect

Spinal respiratory MNs - intercostal muscles and diaphragm - pumping action of lungs

Question 3

How is phrenic nerve activity linked to breathing?

Answer 3

Activity bursts for inspirations

Activity pauses for expirations

Question 4

When do vagus nerve activity bursts start?

Answer 4

At end of phrenic nerve activity bursts - post-inspiratory

Question 5

What is respiratory sinus arrhythmia?

Answer 5

Increased heart rate during inspiration

Decreased heart rate during expiration

Question 6

Name the 3 phases of respiration

Answer 6

Inspiration
Post-inspiration (passive expiration)
Expiration (active expiration)

Question 7

The synchronised activity burst in inspiration involves which nerves?

Answer 7

Phrenic
Glossopharyngeal
Superior laryngeal
Hypoglossal

Question 8

What are the 3 types of brainstem respiratory neurons and when do they fire?

Answer 8

Vi - during inspiration
Ve - during expiration
Phase-spanning - in both phases

Question 9

Which muscles contract during inspiration?

Answer 9

Diaphragm

Question 10

Which muscles contract during post-inspiration?

Answer 10

Laryngeal muscles - control air outflow

Question 11

Which muscles contract during expiration?

Answer 11

Intercostal and abdominal muscles

Question 12

What are the characteristics of eupnea?

Answer 12

Sequential activation of respiratory muscles innervated by cranial and spinal nerves
Synchronised discharge of phrenic and hypoglossal nerves in inspiration
Vagus nerve discharge in post-inspiration

Question 13

What are the characteristics of gasping?

Answer 13

Rapidly decreasing synchronous activation of respiratory muscles innervated by cranial and spinal nerves
Synchronised discharge of phrenic, hypoglossal, vagus nerve in inspiration

Question 14

What is the role of the nucleus of solitary tract?

Answer 14

Receives inputs from peripheral chemoreceptors and airway mechanoreceptors

Question 15

What is the role of the rostral ventral respiratory group (rVRG) and the cVRG?

Answer 15

Motor output to spinal respiratory MNs

Question 16

When does the Botzinger complex burst?

Answer 16

During phrenic nerve pauses

Question 17

When does the rVRG burst?

Answer 17

During phrenic nerve bursts - synchronised

Question 18

What is the role of the pre-Botzinger complex?

Answer 18

Respiratory rhythm generator

Question 19

Which nucleus does the pre-Botzinger complex project to?

Answer 19

Hypoglossal nucleus

Question 20

Which receptor is expressed by inspiratory pre-Botzinger complex neurons?

Answer 20

Neurokinin-receptor 1 (NKR1)

Question 21

What is the effect of a bilateral elimination of NKR1-expressing neurons in the Pre-Botzinger complex?

Answer 21

Ataxic breathing - irregular breathing pattern - random large and small breaths - periods of apnea

Question 22

What is the effect of a unilateral elimination of NKR1-expressing neurons in the Pre-Botzinger complex?

Answer 22

Disrupts breathing during sleep

Question 23

What are rVRG neurons and where do they terminate?

Answer 23

Inspiratory neurons

Terminate in phrenic nerve

Question 24

What are cVRG neurons and where do they terminate?

Answer 24

Expiratory neurons

Terminate in T1-L3 of spinal cord

Question 25

Name and describe the stages of group pacemaker hypothesis of PBC rhythm generation

Answer 25

Post-burst hyperpolarisation - neurons refractory - excitatory synapses in network inactive
Recovery - most excitable neurons recover - spike at low rate
Recurrent excitation - Highly excitable neurons synaptically activate others - recurrent synaptic excitation - causes aggregation of network activity - positive feedback
Burst - inspiratory burst - once critical number of cells in network activated by recurrent excitation

Question 26

How does increasing CO2 levels affect Pre-Botzinger complex activity?

Answer 26

Increases firing frequency