Neural control of Breathing Flashcards
How is the basic pattern of ventilation (i.e. how often and how deep to breath) determined?
The medulla and pons called the central pattern generator (CPG), sometimes also referred to as the “respiratory pattern generator” (RPG)
How is the behaviour of the CPG modulated?
By afferent inputs from various receptors and sensors within the body, which provide feedback regarding the necessary level of ventilation required to maintain healthy CO2, O2, and pH levels.
How is breathing also subject to voluntary control and affected by extreme emotional states?
Inputs from higher somatic and emotional centres also feed into the CPG,
Why can we not voluntarily asphyxiate ourselves by holding our breath?
As either the urge to breath caused by excess CO2 will be overpowering, or acute hypoxaemia will result in loss of consciousness (at which point involuntary breathing will begin).
What is the role of chemoreceptors in regulating respiration?
The central pattern generator receives inputs from central and peripheral chemoreceptors (specialised
receptors that detect levels of CO2, O2, and pH) and initiates compensatory changes in ventilation.
What do central respiratory chemoreceptors (CRC) located within the medulla do?
They indirectly monitor changes in PaCO2 by responding to changes in the pH of the cerebrospinal fluid (CSF). CO2 can pass through the blood-brain barrier, as it is not charged, in to the CSF where it will then react to produce carbonic acid and the resulting H+ activates CRCs.
Where are peripheral chemoreceptors found?
in carotid and aortic bodies
What do peripheral chemoreceptors detect and how are they activcated?
levels of O2, CO2 and pH within arterial blood.
They are activated by low PaO2, high PaCO2 and low pH
Other than signals from chemoreceptors and higher brain centres, what other inputs does the respiratory pattern generator (RPG) use?
Stretch receptors within the lungs that prevent damage due to over-inflation.
Irritant receptors within the airways that initiate cough.
What is sleep apnoea?
Periods of temporary (>10 seconds) cessation of breathing during sleep that can produce significant health defects in affected individuals.
Sleep apnoeas can be categorised as central, obstructive or mixed based on the pathological defect.
What is obstructive sleep apnoea?
caused by temporary blockade of upper respiratory tract e.g due to:
- increase pressure on neck due to increased, obesity-related, fat deposition.
- individual variation in facial structures, displacing the genioglossus (a muscle of the tongue) into the airway.
- fluid moving from the legs to the head and neck due to position during sleep swelling pharyngeal tissue.
What are the risk factors for obstructive sleep apnoea?
Obesity - increased fat deposition, greater pressure on upper respiratory structures
Alcohol/sedatives - general decrease in muscle tone
Smokers - irritation/inflammation of upper respiratory structures
What is central sleep apnoea?
caused by dysfunction in the central nervous system processes that initiate breathing, causing cessation of the automated breathing during sleep (either temporarily or permanently) as the pathways involved in initiating breathing can no longer function.
How can obstructive and central sleep apnoea be differentiated?
Through polysomnography “a type of sleep study”
OSA - increases diaphragmatic effort
CSA - failure of the diaphragm to respond to apnoea (temporary cessation of the CNS-respiratory muscle pathway)
