Nervous Control Of Ventilation

Question 1

What does neural regulation of ventilation do?

Answer 1

Sets the rhythm and pattern of ventilation

Controls the respiratory muscles

Question 2

Is neural or chemical regulation a faster response?

Answer 2

Neural: fast acting impulses to and from the central nervous system
Chemical: detecting changes to pCO2 and O2

Question 3

What are the respiratory control systems?

Answer 3

Medulla - Dorsal respiratory group 
              - Ventral respiratory group
Pons - pneumotaxic centre
         - apneustic centre
Vagus nerve

Question 4

What does the dorsal respiratory group do?

Answer 4

Fibres from the DRG innervate the diaphragm and external intercostal muscles
D contraction and TC expansion = inspiration
DRG neurons switch on for 2s and off for 3s (expiration), causing a rhythmic pattern

Question 5

What does the ventral respiratory group do?

Answer 5

Fibres from VRG innervate the abdominal muscles and internal intercostal muscles
Activity enhanced during forced expiration - promoted by activating VRG, sending signal down to iims

Question 6

What does the pneumotaxic centre do?

Answer 6

Transmits signals to the DRG 
Limits inspiration 
Fine-tunes breathing, sends inhibitory impulses to the DRG
Limits inspiration to 2s
Prevents over-inflation of the lungs

Question 7

What does the apneustic centre?

Answer 7

Responsible for prolonged inspiratory gasps (apneusis)
Prolong DRG stimulation
Not clear on involvement in normal human respiration
Apneusis observed in severe brain injury (activated when something goes wrong)

Question 8

What does the vagus nerve do?

Answer 8

Sends afferent (periphery to central) information from the lungs to DRG 
Role is to prevent over inflation of the lungs by switching off inspiration 
Parasympathetic, similar to pneumotaxic centre

Question 9

What higher brain centres are involved in respiratory control?

Answer 9

Cerebral cortex

Hypothalamus

Question 10

What does the cerebral cortex do?

Answer 10

stimulates motor neurons of inspiratory muscles

bypasses medullary centres when consciously controlling breathing eg. holding breath

Question 11

How is the cerebral cortex’s ability limited?

Answer 11

respiratory centres automatically reinitiate breathing when O2 concentration in the blood reach critical levels

Question 12

What does the hypothalamus do?

Answer 12

strong emotion, pain, changes in temp can alter respiration rate and rhythm
apnoea - anger, pain, decrease in temp
tachypnoea - excitement, increase in temp

Question 13

What is involved in respiratory reflexes?

Answer 13

3 receptors:

stretch, juxtapulmonary, irritant

Question 14

Stretch receptors

Answer 14

located in smooth muscle of trachea and bronchi
sensitive to lung expansion -> respiratory centre -> inspiration becomes shorter and shallower
prevetns overinflation of lungs

Question 15

Juxtapulmonary receptors

Answer 15

‘J’ or C-fibre receptors
lie in alveolar wall between the epithelium and endothelium - close to pulmonary capillaries
stimulated by congestion, oedema, histamine
activation causes apnoea, rapid shallow breathing, bronchoconstriction, mucus secretion

Question 16

Irritant receptors

Answer 16

located between epithelial cells
sensitive to irritant gases, smoke and dust
activation results in rapid shallow breathing, cough, bronchoconstriction, mucus secretion, augmented breaths (gasps)