Control Of Ventilation Flashcards
what does the control of ventilation refer to?
the physiological control of air getting into and out of the lungs
what are three characteristics of ventilatory control?
-is involuntary yet requires sensory input from the brain which controls innervation of skeletal muscles required during inspiration (diaphragm & external intercostals) through alpha motor neurone innervation
diaphragm - phrenic nerve
external intercostals- intercostal nerves
-external intercostals not necessarily required for breathing but diaphragm is - cannot breathe without it
if the spinal cord is severed at any point higher than C3-5 (phrenic nerve roots), breathing will cease
-ventilatory control resides in ill defined respiratory centres in the pons and medulla in the brainstem
what are 2 functions of respiratory centres?
- can regulate rhythm of breathing through smooth and rapid bursts of APs in DRG
- can alter rhythm according to stimuli
what are the 2 main respiratory centres?
Dorsal Respiratory Group
Ventral Respiratory Group
in what ways can respiratory centres have their rhythm modulated?
- Emotion –> via the limbic system
- Higher brain centres –> higher centres such as the cerebral cortex can override the normal respiratory centres
- Mechano-sensory input from thorax –> i.e. stretch reflex which stops lungs from expanding too much
- Chemical component of blood –> this is the MOST SIGNIFICANT way - detected by chemoreceptors
what are the 2 main types of chemoreceptors?
central and peripheral
where are central chemoreceptors found, what do they respond to and how significant are they?
- medulla
- respond to changes in CSF H+
- primary ventilatory drive
where are peripheral chemoreceptors found, what do they respond to, and how significant are they?
- carotid and aortic bodies
- repsond to changes in plasma H+ and PaO2
- secondary ventilatory drive
where are aortic bodies found?
on the aortic arch - they are the more sensitive of the two
where are carotid bodies found?
in the carotid arteries, where they split into internal & external
how do central chemoreceptors respond to an increase in H+ ?
when arterial PCO2 increases, co2 diffuses into the CSF in the brain and dissociates into bicarbonate and hydrogen ions. The central chemoreceptors detect this increase in hydrogen ions and feed back via the respiratory centres to increase ventilation.
how do peripheral chemoreceptors respond to a decrease in plasma pH (H+ increases)- acidosis?
ventilation will be stimulated
how do peripheral chemoreceptors respond to an increase in plasma pH (H+ falls)- alkalosis?
ventilation will be inhibited
what are 2 drugs which affect respiratory centres?
barbiturates and opioids- depress respiratory centres
how does NO affect respiratory rate?
NO blunts peripheral chemoreceptor response to falling PaO2 - can be problematic in people with chronic lung disease on hypoxic drive who solely rely on peripheral (oxygen) chemoreceptors.
