Control of Ventilation Flashcards
What muscles does ventilation require use of?
Skeletal muscles of inspiration (external intercostals and diaphragm)
What is the nerve that innervates the diaphragm?
Phrenic
What nerves innervate the intercostal muscles during inspiration?
Intercostal nerves
Where are the respiratory centres?
- Pons - Medulla
If you severe the spinal chord above C3-5 what happens?
Breathing stops
What 2 conditions do the respiratory centres work in?
- Set an automatic breathing rhythm - Adjust breathing rhythm in response to stimulus
How do the respiratory centres keep an automatic breathing rhythm?
- Constant regular AP’s in the dorsal respiratory group
What 4 things regulate the respiratory system (think about times when your breathing rate increases?)
- Emotion (limbic system) - Voluntary override - Mechanosensory (exercise, stretch reflex) - Chemical composition (PCO2 etc.)
What receptors detect a change in the chemical composition of the blood?
Chemoreceptors
What is the VRG?
Ventral Respiratory Group
What is the DRG?
Dorsal Respiratory Group
What does the VRG control?
- Tongue - Pharynx - Larynx - Expiratory muscles
What does the DRG control?
- Inspiratory muscles
Where are central chemoreceptors found?
Medulla
What do central chemoreceptors respond to and how do they respond?
- H+ in the CSF - Primary ventilatory drive (increase in ventilation
Where are peripheral chemoreceptors?
- Carotid - Aorta
What do peripheral chemoreceptors respond to?
- Plasma H+ - Plasma PCO2 and PO2 (not as much)
What is the reaction of peripheral chemoreceptors?
Secondary ventilatory drive
What does H+ directly show if it is raised?
PCO2 is also high
What is raised PCO2 called?
Hypercapnea
How are central chemoreceptors able to detect PCO2?
- CO2 can cross blood brain barrier - Dissociates into H+ and HCO3 - H+ detected by chemoreceptor
When do peripheral chemoreceptors cause a reflex stimulation of ventilation?
- When blood PO2 is very low - A rise in H+ conc
If acidosis occurs, what will happen to ventilation through chemoreceptors?
Ventilation increases
If alkalosis occurs, what will happen to ventilation?
Will be reduced
Where do all pathways that have a reflex control of ventilation converge?
Medulla Oblongata
How are the signals from the carotid and aortic chemoreceptors transferred to the medulla?
Afferent sensory neurons
What neurones are activated by the medulla to cause inspiration and expiration?
Somatic motor neurons
What structures are innervated by somatic inspiratory neurones?
- Diaphragm - External intercostals - Scalene and sternocleidomastoid
What structures are innervated by the somatic expiratory nerves?
- Internal intercostals - Abdominal muscles
STUDY THIS DIAGRAM
What other part of the brain has descending neural pathways that allow voluntary breathing control?
Central Cortex
What drugs depress the respiratory centre?
- Barbiturates
- Opioids
What happens to respiration after swallowing?
- Initial breath out to move particles from airway at epiglottis
- Ventilation is inhibited
