Control of Breathing Flashcards
Why is breathing a unique behaviour?
- It is continuous from birth to death
- It occurs spontaneously - does not need conscious thought unless there is a problem
What is breathing modulated by?
Reflexes - coughing Volitional control - Breath hold Vocalisation - singing Emotional events - crying - Physiological challenges - Sleep, exercise
What must neural control of breathing do?
- Establish autonomic rhythm: breathing happens without conscious thought
- Respond to metabolic demands
- Respond to mechanical changes: change in posture
- Range of episodic non-ventilatory behaviours: speaking, sniffling, eating
What is Eupnea?
Normal rhythmic breathing
What is Dyspnea?
- Being short of breath
- Unpleasant conscious awareness of difficulty breathing
What are respiratory related neurons?
- Array of interconnected neurons
- Fire more action potentials during the respiratory cycle
What are central pattern generators?
- Brainstem (medulla oblongata)
- Independently generate respiratory rhythm
What are respiratory motor neurons?
- Innervate respiratory muscles
- Axons via the phrenic nerve innervate the diaphragm
What does the frequency of respiratory central pattern generators change?
- The strength of drive from central and peripheral receptors
- Change in both depth and frequency of ventilation
What do chemoreceptors provide feedback on in the respiratory system (to the brain)?
On the PO2, PCO2 and pH
What do mechanoreceptors provide feedback on in the respiratory system (to the brain)?
Mechanical status of the lungs, chest wall and airways
What does neural signals sent to respiratory muscles do?
They produce rhythmic breathing movements e.g. diaphragm and intercostals
What does neural signals sent to upper airway muscles do?
e. g. laryngeal, pharyngeal and tongue
- Produce reflexes to keep airways patent (clear, prevent obstruction) e.g. cough, gag, sneeze
What are chemoreceptors?
Sensory receptors that detect chemical changes in the surrounding environment
- In the respiratory system chemoreceptors detect changes in PO2, PCO2 and pH of the blood
- decreases in O2 - hypoxia
- decreases in CO2 - hypercapnia
What are peripheral chemoreceptors?
- Small, highly vascularised bodies in the region of the aortic arch and carotid sinuses
- Information is sent via the glossopharyngeal and vagus nerve to the nucleus in the brain stem (NTS)
What is the name of the nucleus in the brainstem?
Nucleus Tractus Solitarius
What do peripheral chemoreceptors respond to?
Decreases in Po2 - hypoxia
- Reduction in arterial PO2
- Peripheral chemoreceptors stimulated
- Neural signals sent from carotid and aortic bodies to NTS in the brainstem
- Ventilation increases to restore PO2 levels