PSC1002/L18 Control of Respiration

Question 1

Where is the respiratory control centre?

Answer 1

Medulla and pons (brainstem)

Question 2

What is the role of the medulla with regards to respiration?

Answer 2

Generates automatic rhythmic breathing pattern

Question 3

What are the 2 groups of neurones in the medulla?

Answer 3

Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)

Question 4

Activation of which neurones generates automatic rhythmic breathing?

Answer 4

DRG

Question 5

Where is the apneustic centre and what is its function? (2)

Answer 5

Dorsally in pons
Promotes inspiration by stimulating inspiratory neurones in medulla

Question 6

Where is the pneumotaxic centre and what is its function? (3)

Answer 6

Upper part of pons
Antagonists and dominates apneustic centre
Inhibits inspiration & allows for smooth breathing

Question 7

Where are peripheral chemoreceptors located? (2)

Answer 7

Aortic bodies on aortic arch
Carotid bodies in bifurcation of internal and external carotid artery

Question 8

Via which nerves do peripheral chemoreceptors transmit information?

Answer 8

Aortic - vagus nerve
Carotid - glossopharyngeal nerve

Question 9

What do peripheral chemoreceptors sample in blood? (3)

Answer 9

O2
CO2
H+

Question 10

Describe the signalling pathway within the carotid body. (7)

Answer 10

Low PO2
K+ channels close
Cell depolarises
VG Ca2+ channels open
Ca2+ enter cell
Exocytosis of DA vesicles
AP in sensory neurone

Question 11

How does PCO2 affect respiratory rate?

Answer 11

Increase PCO2 = increase respiratory rate

Question 12

Describe indirect sensing of PCOs by central chemoreceptors. (2)

Answer 12

Increased PCO2 in CSF generates H+
H+ stimulates chemoreceptor

Question 13

What response occurs from increased PCO2/H+ in blood?

Answer 13

Hyperventilation

Question 14

Describe how hyperventilation results in respiratory alkalosis. (5)

Answer 14

More CO2 expired
Blood CO2 decreases
Carbonic acid released fewer H+
[H+] decreases
Blood pH increases

Question 15

What is metabolic acidosis?

Answer 15

Acidosis resulting from an increase in non-CO2 derived acid
E.g., lactic acid produced during exercise

Question 16

Why does metabolic acidosis not stimulate central chemoreceptors?

Answer 16

H+ ions can’t penetrate blood brain barrier

Question 17

Describe the body’s response to metabolic acidosis. (3)

Answer 17

Increased respiration
Increased excretion of CO2
Reduces acid load in blood

Question 18

Describe the Hering Breuer Reflex. (2)

Answer 18

Prevents over-inflation of lung
Activation of stretch receptors in lung SM cessate inspiration

Question 19

What is the role of irritant receptors? (4)

Answer 19

Stimulated by mechanical stimuli, inhaled dusts etc.
Rapid adaptation when continuously stimulated
Impulses via myelinated fibres in vagus
Rapid shallow breaths and cough reflex

Question 20

How is cough initiated by irritant receptors? (7)

Answer 20

Impulse via vagus and superior laryngeal nerves to medulla activated
Diaphragm and external intercostal muscles contract
Pressure in pleural cavity decreases
Glottis and larynx close
Abdominal and other muscles contract at high speed
Glottis and larynx open
Air released at high speed
Bronchi and non-cartilaginous trachea collapes
Air forced through narrow openings clearing any irritants

Question 21

What is the role of proprioception in respiration?

Answer 21

Anticipates increased requirement for oxygen/removal of CO2 exercise requires