Lung Physiology 4: Control of respiration

Question 1

Why is respiration required?

Answer 1

• Ensure haemoglobin is as close to full saturation with oxygen as possible
• Efficient use of energy resource
• Regulate PaCO2 carefully

Question 2

What input signals and receptors enter the respiratory control centres (medulla and pons)

Answer 2

• Central chemoreceptors
• Voluntary control (cerebrum)
• Lung receptors
• Muscle proprioreceptors
• Peripheral chemoreceptors

Question 3

Where do signals from the medulla and pons go?

Answer 3

Through spinal motor neurons to:
- Muscles of respiration
- Accessory muscles
- Diaphragm

Question 4

What is the Pre-Botzinger complex?

Answer 4

pacemaker cells located in superior ventral respiratory group, acting as breathing rhythm generator.

Question 5

What are the two centres in the pons controlling breathing?

Answer 5

Pneumotaxic and apneustic

Question 6

What are the two main groups in the medulla oblongata that generates the basic pattern?

Answer 6

Dorsal respiratory group and ventral respiratory group

Question 7

What does the dorsal respiratory group do?

Answer 7

• Predominantly active during inspiration
• inspiratory neurones that stimulate diaphragm and external intercostals

Question 8

What does the ventral respiratory group do?

Answer 8

• Active in both inspiration and expiration
• centre for forced inspiration and expiration. Stimulates accessory muscles of ventilation and inhibits apneustic centre

Question 9

What is the central pattern generator?

Answer 9

Neural network (interneurons)
Located within DRG/VRG
Start, stop and resetting of an integrator of background ventilatory drive

Question 10

How is inspiration stimulated?

Answer 10

• Progressive increase in inspiratory muscle activation
• Lungs fill at a constant rate until tidal volume achieved
• End of inspiration, rapid decrease in excitation of the respiratory muscles

Question 11

How is expiration stimulated?

Answer 11

Largely passive due to elastic recoil of thoracic wall
- First part of expiration; active slowing with some inspiratory muscle activity
- With increased demands, further muscle activity recruited
- Expiration can be become active also; with additional abdominal wall muscle activity

Question 12

What are the two groups of chemoreceptors?

Answer 12

• Central (60% influence from PaCO2)
• Peripheral (40% influence from PaCO2)

Question 13

What are chemoreceptors?

Answer 13

Tells your body to take a breath

Question 14

What stimulates central chemoreceptors?

Answer 14

• H+ conc and gas arterial pressures in blood
• Brainstem (primary influence is PaCO2)

Question 15

Where are central receptors located?

Answer 15

Central receptors at pontomedullary junction in brainstem, peripheral in bifurcation of carotid arteries (CNIX) and in aortic arch (CNX)

Question 16

What do central and peripheral receptors respond to?

Answer 16

Central - CO2
Peripheral - O2

Question 17

Where are peripheral chemoreceptors located?

Answer 17

• Carotid bodies and aortic bodies

Question 18

What happens to peripheral chemoreceptors when exposed to hypoxia?

Answer 18

• Responsible for ventilatory response to hypoxia
• When exposed to hypoxia, type I cells release neurotransmitters that stimulate the cup-like endings of the carotid sinus nerve

Question 19

What are the three types of lung receptors?

Answer 19

Stretch, Juxtapulmonary and irritant
- Combination of slow and fast adapting receptors
- Assist with lung volumes and responses to noxious inhaled agents

Question 20

What are some features of the stretch lung receptors?

Answer 20

• Smooth muscle and they can sense lung volume, slowly adapting

Question 21

What are some features of irritant lung receptors?

Answer 21

• larger conducting airways, rapidly adapting (cough, gasp), can stimulate long, deep breathing

Question 22

What are some features of Juxtapulmonary receptors?

Answer 22

Pulmonary and bronchial C fibres and responds to irritants. Cause rapid and shallow breathing