Lung Physiology 4: Control of respiration Flashcards
Why is respiration required?
- Ensure haemoglobin is as close to full saturation with oxygen as possible
- Efficient use of energy resource
- Regulate PaCO2 carefully
What input signals and receptors enter the respiratory control centres (medulla and pons)
- Central chemoreceptors
- Voluntary control (cerebrum)
- Lung receptors
- Muscle proprioreceptors
- Peripheral chemoreceptors
Where do signals from the medulla and pons go?
Through spinal motor neurons to:
- Muscles of respiration
- Accessory muscles
- Diaphragm
What is the Pre-Botzinger complex?
pacemaker cells located in superior ventral respiratory group, acting as breathing rhythm generator.
What are the two centres in the pons controlling breathing?
Pneumotaxic and apneustic
What are the two main groups in the medulla oblongata that generates the basic pattern?
Dorsal respiratory group and ventral respiratory group
What does the dorsal respiratory group do?
- Predominantly active during inspiration
- inspiratory neurones that stimulate diaphragm and external intercostals
What does the ventral respiratory group do?
- Active in both inspiration and expiration
- centre for forced inspiration and expiration. Stimulates accessory muscles of ventilation and inhibits apneustic centre
What is the central pattern generator?
Neural network (interneurons)
Located within DRG/VRG
Start, stop and resetting of an integrator of background ventilatory drive
How is inspiration stimulated?
- Progressive increase in inspiratory muscle activation
- Lungs fill at a constant rate until tidal volume achieved
- End of inspiration, rapid decrease in excitation of the respiratory muscles
How is expiration stimulated?
Largely passive due to elastic recoil of thoracic wall
- First part of expiration; active slowing with some inspiratory muscle activity
- With increased demands, further muscle activity recruited
- Expiration can be become active also; with additional abdominal wall muscle activity
What are the two groups of chemoreceptors?
- Central (60% influence from PaCO2)
- Peripheral (40% influence from PaCO2)
What are chemoreceptors?
Tells your body to take a breath
What stimulates central chemoreceptors?
- H+ conc and gas arterial pressures in blood
- Brainstem (primary influence is PaCO2)
Where are central receptors located?
Central receptors at pontomedullary junction in brainstem, peripheral in bifurcation of carotid arteries (CNIX) and in aortic arch (CNX)
What do central and peripheral receptors respond to?
Central - CO2
Peripheral - O2
Where are peripheral chemoreceptors located?
- Carotid bodies and aortic bodies
What happens to peripheral chemoreceptors when exposed to hypoxia?
- Responsible for ventilatory response to hypoxia
- When exposed to hypoxia, type I cells release neurotransmitters that stimulate the cup-like endings of the carotid sinus nerve
What are the three types of lung receptors?
Stretch, Juxtapulmonary and irritant
- Combination of slow and fast adapting receptors
- Assist with lung volumes and responses to noxious inhaled agents
What are some features of the stretch lung receptors?
- Smooth muscle and they can sense lung volume, slowly adapting
What are some features of irritant lung receptors?
- larger conducting airways, rapidly adapting (cough, gasp), can stimulate long, deep breathing
What are some features of Juxtapulmonary receptors?
Pulmonary and bronchial C fibres and responds to irritants. Cause rapid and shallow breathing
