Neural Control Of Breathing Flashcards
Why do you need to modulate the rate of ventilation?
Efficiency
If you expel too much CO2, alkylysis is caused
How are the right balances in blood gases maintained?
By maintaining pressure gradients between alveoli and blood
Why does the O2 demand increase in exercise?
Increased ATP production, and increased consumption of O2
Ventilation=
Tidal volume x respiratory rate
Why does just hyperventilating not have much effect on O2 delivery?
Hb is 98% saturated at rest so hyperventilating won’t change that
What provides the contractile signal for the respiratory muscles?
Innervation from motor neurones that synapse from the descending spinal tract
What muscles are used in inspiration?
In quiet breathing: diaphragm
Increased/forced inspiration: external intercostals, pectorals, sternomastoid and scalene
What muscles are used in expiration?
In quiet breathing: elastic recoil
Increased/forced ventilation: elastic recoil, internal intercostals and abdominals
What is the breathing pattern generated by?
Neuronal systems within the brainstem
What things do the central pattern generator use to determine the rate and depth of breathing?
- cerebral cortex
- pain and emotional stimuli (hypothalamus)
- peripheral chemoreceptors increase breathing
- central chemoreceptors increase
- receptors in muscles and joints increase
- stretch receptors in lungs inhibit
- irritant receptors inhibit
How do central chemoreceptors indirectly respond to changes in arterial pCO2?
They monitor arterial CO2 in the medulla
Why do central respiratory chemoreceptors not respond to changes in [H+]?
H+ doesnt cross the blood brain barrier
What are peripheral chemoreceptors activated by?
Decreased paO2 and increased paCO2
What do peripheral chemoreceptors do when activated?
Signal to respiratory centres in medulla to increase ventilation
Where are peripheral chemoreceptors found?
Carotid artery and aortic bodies
What happens when you fall asleep (relating to ventilation)?
- decreased metabolic rate (as less respiratory demands)
- postural changes alter the mechanics of breathing
- decreased SNS and increased PNS tone
- decreased heart rate, blood pressure and cardiac output
- decreased tidal volume, breathing frequency and minute volume
- decreased O2 and increased CO2 concs
What can cause ventilation disfunction (6)?
- trauma
- stroke
- drugs
- congenital central hypoventilation syndrome
- neonates
- altitude
How can trauma cause respiratory malfunction?
Damage to respiratory centres in the brain stem
How can a stroke cause respiratory malfunction?
Ischaemia-induced brainstem tissue injury
How can drugs (eg opioids) cause respiratory malfunction?
Suppression of neuronal activity
Why may neonates suffer from respiratory malfunction?
Incomplete development of respiratory centres prior to birth
How can altitude cause respiratory malfunction?
Control systems unable to cope with abnormal atmospheric environment (low O2 and CO2)
What is sleep apnoea?
Temporary stopping of breathing during sleep
What is the minimum and maximum length and regularity of sleep apnoea periods?
5-160 per hour
10-90 seconds
What are the health effects of sleep apnoea?
- Tiredness (poor sleep quality)
- CV complications (stress + increased SNS tone)
- obesity/diabetes (inflammation and metabolic disfunction)
What is cheyne-stokes respiration?
Oscillating apnoea and hyperapnoea (stopping breathing then hyperventilating)
What are the steps in cheyne-stokes respiration?
(It’s a circle but)
Hypercapnia/hypoxaemia -> compensatory hyperventilation -> hypercapnia+ alkalosis -> decreased respiratory drive -> compensatory hypoventilation -> (back to start)
