Respiratory Physiology - Control of ventilation - chemoreceptors Flashcards
What type of muscle control breathing?
Voluntary skeletal muscles
Wha nerve innervates the diaphragm for breathing?
Phrenic nerve
What nerve inner ages the external intercostal muscles during inspiration?
Intercostal nerves
What are the brain stem respiratory centres?
Resides within the defined centres located in the pons and medulla
What happens if you sever the phrenic nerve above C3?
Breathing ceases
What do the respiratory centres set?
Intrinsic control of breathing
Basal rhythm
What modulates the rhythm of the respiratory system?
- Emotion (via lambic system)
- Voluntary override (via higher centres in brain)
- Mechanic-sensory input from the thorax (e.g. stretch reflex/ threshold reached)
- Chemical compost of the blood (PCO2, PO2 and pH detected by chemoreceptors)
What is the limbic system?
the part of the brain involved in our behavioural and emotional responses,
What are the 2 major groups of neurones in the respiratory system?
DRG (dorado respiratory group)
VRG (ventral respiratory group)
What does the VAR INNERVATE?
Tongue
Pharynx
Larynx
Expiratory muscles
What does the DGR innervate?
Inspiration muscles
How does the DRG innervate muscles?
Via phrenic and intercostal nerves
What input most significantly affects the VRG and DRG?
Chemoreceptors
What are the 2 types of chemoreceptors?
Central
Peripheral
Where are the central chemoreceptors?
Medulla
Where are the peripheral chemoreceptors?
Carotid and aortic bodies
What allows for a smooth, low and controlled expiration?
Basal tone in expiratory muscles
VGR
What do the central chemoreceptors respond to?
Hydrogen ions
What do the H+ that the central chemoreceptors come from?
CO2
Reflect PCO2 level
Are we sensitive to the change in H+ in cerebral spinal fluid?
Yes
What do the H+ ions reflect ?
The PCO2 in systemic arterial blood
What do the peripheral chemoreceptors directly respond to?
PO2 and plasma [H+]
Less so to PCO2
What chemoreceptor is the primary ventilators drive?
Central
What is the chemoreceptor is the secondary ventilators drive?
Peripheral
Where are the H+ found which are detected by central chemoreceptors?
CSF
Cerebral spinal fluid which surround the brain
How is the car regulated?
Blood brain Barrier
How do the central chemoreceptors responds to changes in [H+]?
Increase rate and depth of breathing
What happens when there is an increase in [H+]?
Reflex stimulation
What drives the increase in [H+]?
Increase in PCO2 of systemic arterial blood supplying the brain
What is it called when there is an increase in PCO2 in the systemic blood?
Hypercapnea
What is hypercapnea?
Increase in PCO2in systemic arterial blood
What does CO2 and H2O (plasma) form?
Carbonic acid
H2CO3
What does carbonic acid dissociate to?
H+ and HCO3-
Can central chemoreceptors respond to H+ in plasma?
No
Only car
What causes reflex inhibition?
A decrease in arterial PCO2 (reduces CSF ([H+]) (hyperventilation)
Long deep breaths
How does the brain maintain a stability composition of the CSF?
Not allow ions to cross
What can and cannot travel from the arteries into the CSF?
CO2 can move in
H+ cannot
What happens when CO2 crosses the blood brain barrier?
Dissociation and H+ formed as byproduct
Once the CO2 dissociates and forms h+ in the CSF, what detects it?
Central chemoreceptors
What is the effect of H+ stimulating central chemoreceptors?
Stimulate respiratory control centre and increase ventilation
Reduces the pco2 of CO2
Need more oxygen, H+ reflects higher PCO2
Why do we want to regulate the levels of CO2 in the blood?
CO can be produced and that is toxic
High affinity for haemoglobn and reduce the amount of O2 that can bind
Are we sensitive to small changes in co2?
Yes
Small changes in CO2 mean large changes in ventilation to help get rid of the CO2 and reduce toxic CO
