Control of Ventilation

Question 1

What muscles does ventilation require use of?

Answer 1

Skeletal muscles of inspiration (external intercostals and diaphragm)

Question 2

What is the nerve that innervates the diaphragm?

Answer 2

Phrenic

Question 3

What nerves innervate the intercostal muscles during inspiration?

Answer 3

Intercostal nerves

Question 4

Where are the respiratory centres?

Answer 4

• Pons - Medulla

Question 5

If you severe the spinal chord above C3-5 what happens?

Answer 5

Breathing stops

Question 6

What 2 conditions do the respiratory centres work in?

Answer 6

• Set an automatic breathing rhythm - Adjust breathing rhythm in response to stimulus

Question 7

How do the respiratory centres keep an automatic breathing rhythm?

Answer 7

• Constant regular AP’s in the dorsal respiratory group

Question 8

What 4 things regulate the respiratory system (think about times when your breathing rate increases?)

Answer 8

• Emotion (limbic system) - Voluntary override - Mechanosensory (exercise, stretch reflex) - Chemical composition (PCO2 etc.)

Question 9

What receptors detect a change in the chemical composition of the blood?

Answer 9

Chemoreceptors

Question 10

What is the VRG?

Answer 10

Ventral Respiratory Group

Question 11

What is the DRG?

Answer 11

Dorsal Respiratory Group

Question 12

What does the VRG control?

Answer 12

• Tongue - Pharynx - Larynx - Expiratory muscles

Question 13

What does the DRG control?

Answer 13

• Inspiratory muscles

Question 14

Where are central chemoreceptors found?

Answer 14

Medulla

Question 15

What do central chemoreceptors respond to and how do they respond?

Answer 15

• H+ in the CSF - Primary ventilatory drive (increase in ventilation

Question 16

Where are peripheral chemoreceptors?

Answer 16

• Carotid - Aorta

Question 17

What do peripheral chemoreceptors respond to?

Answer 17

• Plasma H+ - Plasma PCO2 and PO2 (not as much)

Question 18

What is the reaction of peripheral chemoreceptors?

Answer 18

Secondary ventilatory drive

Question 19

What does H+ directly show if it is raised?

Answer 19

PCO2 is also high

Question 20

What is raised PCO2 called?

Answer 20

Hypercapnea

Question 21

How are central chemoreceptors able to detect PCO2?

Answer 21

• CO2 can cross blood brain barrier - Dissociates into H+ and HCO3 - H+ detected by chemoreceptor

Question 22

When do peripheral chemoreceptors cause a reflex stimulation of ventilation?

Answer 22

• When blood PO2 is very low - A rise in H+ conc

Question 23

If acidosis occurs, what will happen to ventilation through chemoreceptors?

Answer 23

Ventilation increases

Question 24

If alkalosis occurs, what will happen to ventilation?

Answer 24

Will be reduced

Question 25

Where do all pathways that have a reflex control of ventilation converge?

Answer 25

Medulla Oblongata

Question 26

How are the signals from the carotid and aortic chemoreceptors transferred to the medulla?

Answer 26

Afferent sensory neurons

Question 27

What neurones are activated by the medulla to cause inspiration and expiration?

Answer 27

Somatic motor neurons

Question 28

What structures are innervated by somatic inspiratory neurones?

Answer 28

• Diaphragm - External intercostals - Scalene and sternocleidomastoid

Question 29

What structures are innervated by the somatic expiratory nerves?

Answer 29

• Internal intercostals - Abdominal muscles

Question 30

STUDY THIS DIAGRAM

Answer 30

Question 31

What other part of the brain has descending neural pathways that allow voluntary breathing control?

Answer 31

Central Cortex

Question 32

What drugs depress the respiratory centre?

Answer 32

• Barbiturates
• Opioids

Question 33

What happens to respiration after swallowing?

Answer 33

• Initial breath out to move particles from airway at epiglottis
• Ventilation is inhibited