Control of lung function Flashcards
What areas in the medulla oblongata control lung function?
Dorsal respiratory group
Ventral respiratory group
What is the dorsal respiratory group?
Known as inspiratory centre (DIVE)
Situated dorsally in medulla
Function is to set rate of breathing
Receives sensory info from various parts of body which it processes to ensure correct breathing rate is reached
Generates inspiration by activating inspiratory muscles
What is the ventral respiratory group?
Known as expiratory centre (DIVE)
Situated ventrally in medulla
Function is to generate expiration however is inactive during quiet breathing
If breathing rate is increased it will be involved in activating expiratory muscles of respiration initiating forced expiration
Passive recoil of lungs is usually sufficient to ensure breathing out takes place
What areas in the pons control lung function?
Apneustic centre
Pneumotaxic centre
What is the apneustic centre?
Situated inferiorly in pons
Function is to stimulate activity in dorsal respiratory group
Contributes secondary to breathing in
Inhibited by ventral respiratory group and pulmonary afferents
What is the pneumotaxic centre?
Situated superiorly in pons
Known as respiratory off switch
Function is to regulate depth and frequency of breathing
What is the relationship between nuclei in the brainstem?
Dorsal and ventral group work antagonistically
Ventral group inhibits apneustic centre
Pneumotaxic centre inhibits dorsal group
Pneumotaxic and apneustic centre work antagonistically
As you breath in, apneustic group generates increasing freq. of APs. This stimulates dorsal respiratory group to continue stimulating inspiratory muscles
Once the threshold is reached, the pneumotaxic centre takes over- it shuts down inspiration and initiates expiration
How are respiratory muscles innervated?
Respiratory centre in brain generates APs which supply motor nerve innervation to inspiratory and expiratory musculature
Spinal nerves C3, C4, C5 colas to form phrenic nerve- provides motor invention to the diaphragm
During inspiration, diaphragm contracts (pulls down) which reduces intrathoracic pressure making air flow in the lungs
External intercostals are inspiratory muscles
Internal intercostals contribute to forced expiration
What happens to CO2 in blood?
Breathing is important to excrete CO2
CO2 is a weak acid and reacts with water to form carbonic acid which dissociates to H+ and bicarbonate
An increase in H+ ions in blood leads to acidaemia which makes blood more acidic
pH is important for protein structure
What is the impact of CO2 on the brain?
If CO2 is high, pH will decrease
The brain can’t directly lower pH because of the presence of the blood brain barrier
The blood brain barrier is continuous capillaries that border CSF- have tight junctions and glial cells which act as support structures and make them waterproof
Although H+ ions can’t penetrate the barrier, CO2 can cross into CSF and undergo reactions with water to produce carbonic acid which dissociates into H+.
H+ can enter medulla and interact with afferent fibres causing signal to be carried to dorsal respiratory group .
What happens when theres a drop in pH?
A drop in pH is detected by chemoreceptive neurones in medulla
They go on to send info to dorsal respiratory group
What is the role of peripheral chemoreceptors?
They’re found in carotid bodies within the aortic arch and aortic bodies in aortic arch
Carotid body chemoreceptors are innervated by glossopharyngeal nerve
Aortic body chemoreceptors are innervated by vagus nerve
These chemoreceptors detect changes in partial pressure of oxygen, CO2 and changes pH of arterial blood
What are irritant receptors?
Nerve endings which are embedded between epithelial cells in upper airways
Capable of identifying inhaled foreign objects like water
Initiate cough reflex- involves cleansing of epiglottis whilst simultaneously contracting expiratory muscles forcefully
Generates very positive interthoracic pressure which is stabilised by rapid ejection of air
What are stretch receptors?
Found on medium to small airways
If lungs are fully inflated, receptors initiate Hering- Breuer reflex- prevents hyperinflation of lungs
Once activated, reflex results in inhibition of apneustic centre and dorsal respiratory group via vagus nerve- this results in initiation of expiration
What are J receptors?
Aka. pulmonary c. fibres
Detect accumulation of fluid in interstitial space in alveoli (oedema)
In response to stimulation there is increased inspiration
Found next to capillary cells of alveoli
