The Neural Control of Breathing Flashcards
In quiet breathing what muscles are used?
The diaphragm and external intercostal muscles.
What are accessory muscles?
Muscles with other roles that can help in ventilation. For inhalation, these are the sternocleidomastoid and scalene muscles. For exhalation, these are the abdominals.
Where does neural innervation of muscles for breathing start?
In the medulla in the upper motor neurones. These UMN’s project down to the lower motor neurones in the spinal cord.
Which nerve innervates the diaphragm and where does it arise from?
Which nerve region innervates the intercostal muscles?
Phrenic and C3, C4, C5
T1-T12
What are the 2 groups in the respiratory pattern generator? What are they involved in? Where do they originate?
- The Ventral respiratory group - involved in finishing inspiration and expiration - found in medulla oblongata.
- The Dorsal respiratory group - involved in initiating inspiration - found in the medulla oblongata.
How do we breathe?
Nucleus 1 in the DRG tells UMN’s to fire to cause inspiratory LMN’s to fire and initiate inspiration. It also signals nucleus 3, which signals up to the VRG and stimulates the UMN’s here to cause the expiratory LMN’s to fire and allow exhalation to occur after the inspiration that just occurred. There is communication between nucleus 5 and 7 in the VRG and 7 projects down to nucleus 1 to inhale again. There is also inhibition from stretch receptors via the vagus nerve which tells nucleus 1 that the lungs are full and to stop firing.
In what 2 ways can you increase ventilation?
- Increase tidal volume by increasing muscle fibres.
2. You can increase the frequency that you breathe by increased alternation of the RPG - which increases rate.
What is cortical override?
Control of breathing by cortical neurones completely bypass the medulla and go to the LMN’s telling the diaphragm and intercostals to contract. This is conscious control of breathing and overrides our automatic control.
What is congenital central hypoventilation syndrome?
Sufferers have to be awake to sleep as the RPG doesn’t work properly so the patient must rely on cortical override to breathe and must be ventilated when asleep.
What is obstructive sleep apnoea (OSA)?
When there is an obstruction in the upper airway which is usually caused by relaxation of the genioglossus (main muscle of the tongue).
What are the risk factors of OSA?
Alcohol - muscle relaxation Obesity - fat reduces airway diameter Neuromuscular disease - poor control of muscles Strokes - stress MI - stress
What is central sleep apnoea?
Lack of central control of breathing. Could be seen in neonates due to poorly developed CNS. Could be seen in adults due to stroke or drugs that damage respiratory control areas.
What are peripheral chemoreceptors? Where are they found?
Receptors that respond to high PaCO2, low PaO2 and acidaemia. These are found in the carotid body and are linked to the glossopharyngeal nerve IX.
