Control of Respiration Flashcards
Describe central chemoreceptors
Location - medulla oblongata in brainstem
Sensitive - PaCO2 blood (arterial)
When change are detected receptors send impulses to the respiratory centres in the brainstem which initiate change
Increase PaCO2 = increase ventilation - more CO2 exhaled
Decrease PaCO2 = decrease ventilation - CO2 retained in the lungs
What % do central chemoreceptors have on influence of PaCO2
60%
What % do peripheral chemoreceptors have on influence of PaCO2
40%
Describe peripheral chemoreceptors
Location - medulla and pons
Function - responsible for all ventilatory responses to hypoxia (reduced PaO2)
Low levels of oxygen will try adapting to influence pAO2 - main determinant PiO2 which can be hard to change
Describe the route of peripheral chemoreceptors to detect change
Low levels of oxygen detected
Afferent impulses travel via the glossopharyngeal and vagus nerve
Increase respiratory rate and tidal volume
Blood flow directed towards the kidneys and brain
Increase cardiac output
What organs are more sensitive to hypoxia
Kidneys and brain
What are central chemoreceptors sensitive to
PaCO2
What are peripheral chemoreceptors sensitive to
PaO2
Describe mechano-receptors - lung receptors
3 types of lung receptors
- Stretch - sense lung volume, slowly adapting
- J - juxta pulmonary capillary
- Irritant - rapid adapting e.g. cough, gasp
Assist with lung volumes and responses to noxious inhaled agents
Afferent - Vagus Nerve
Combination of slow and fast adapting
Describe mechano-receptors airway
Location
- nose, nasopharynx and larynx
chemo and mechano receptors - pharynx
Appear to be activated in swallowing
Respiratory activity stops when swallowing to protect against the risk of aspiration of food or liquid
What are the chemical receptors for control of respiration
Central chemoreceptors
Peripheral chemoreceptors
Describe involuntary control of respiration
Diaphragm and intercostal muscles - stimulated by group of neurones in pons and medulla
Send impulses to primary respiratory muscles via phrenic and intercostal nerves - stimulate contraction
What are the three main neurones involved in respiration
Ventral respiratory group
Dorsal respiratory group
Pontine respiratory group
What does the ventral respiratory group control
Active in both inspiration and expiration
What does the dorsal respiratory group control
Active during inspiration
What does the pontine respiratory group control
Rate and pattern of breathing
What happens when the neurones involved in involuntary control of respiration stop firing
Inspiratory muscles relax and expiration occurs
Describe voluntary control of respiration
Motor cortex in cerebrum - receives inputs from limbic system and hypothalamus
Thought to be sent from the spinal cord from the motor cortex - passed to respiratory muscles
What are the areas of control in the brainstem
Medulla oblongata and pons
What is the role of the pons in control of respiration
Pneumotaix and apneustic centres
What is the role of the medulla in control of respiration
Phasic discharge of action potentials
Dorsal respiratory group
Ventral respiratory group
Describe the general pattern generator
Located in DRG/VRG
Start, stop and resetting of integrator of background and ventilatory drive
What does PRG (pons) do
Inhibition
What does VRG and DRG do (medulla)
Stimulation
What is respiratory drive
Intensity of output by respiratory centres and determines the effort of respiratory muscles
What causes a lack/loss of respiratory drive
Type 2 respiratory failure - lack
Loss - e.g. opioids
When does alveoli recruitment occur
As a consequence of exercise
More capillaries can be recruited - ones which are not opened up can open up during exercise
Where is the respiratory control centre located
Neurones within the pons and medulla
