PSC1002/L18 Control of Respiration Flashcards
Where is the respiratory control centre?
Medulla and pons (brainstem)
What is the role of the medulla with regards to respiration?
Generates automatic rhythmic breathing pattern
What are the 2 groups of neurones in the medulla?
Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)
Activation of which neurones generates automatic rhythmic breathing?
DRG
Where is the apneustic centre and what is its function? (2)
Dorsally in pons
Promotes inspiration by stimulating inspiratory neurones in medulla
Where is the pneumotaxic centre and what is its function? (3)
Upper part of pons
Antagonists and dominates apneustic centre
Inhibits inspiration & allows for smooth breathing
Where are peripheral chemoreceptors located? (2)
Aortic bodies on aortic arch
Carotid bodies in bifurcation of internal and external carotid artery
Via which nerves do peripheral chemoreceptors transmit information?
Aortic - vagus nerve
Carotid - glossopharyngeal nerve
What do peripheral chemoreceptors sample in blood? (3)
O2
CO2
H+
Describe the signalling pathway within the carotid body. (7)
Low PO2
K+ channels close
Cell depolarises
VG Ca2+ channels open
Ca2+ enter cell
Exocytosis of DA vesicles
AP in sensory neurone
How does PCO2 affect respiratory rate?
Increase PCO2 = increase respiratory rate
Describe indirect sensing of PCOs by central chemoreceptors. (2)
Increased PCO2 in CSF generates H+
H+ stimulates chemoreceptor
What response occurs from increased PCO2/H+ in blood?
Hyperventilation
Describe how hyperventilation results in respiratory alkalosis. (5)
More CO2 expired
Blood CO2 decreases
Carbonic acid released fewer H+
[H+] decreases
Blood pH increases
What is metabolic acidosis?
Acidosis resulting from an increase in non-CO2 derived acid
E.g., lactic acid produced during exercise
Why does metabolic acidosis not stimulate central chemoreceptors?
H+ ions can’t penetrate blood brain barrier
Describe the body’s response to metabolic acidosis. (3)
Increased respiration
Increased excretion of CO2
Reduces acid load in blood
Describe the Hering Breuer Reflex. (2)
Prevents over-inflation of lung
Activation of stretch receptors in lung SM cessate inspiration
What is the role of irritant receptors? (4)
Stimulated by mechanical stimuli, inhaled dusts etc.
Rapid adaptation when continuously stimulated
Impulses via myelinated fibres in vagus
Rapid shallow breaths and cough reflex
How is cough initiated by irritant receptors? (7)
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
What is the role of proprioception in respiration?
Anticipates increased requirement for oxygen/removal of CO2 exercise requires
