Central Control Of Respiration Flashcards
What is respiration rhythm
Respiration is automatic and rhythmic
There is a degree of conscious control
What is the central pattern generator
Pacemaker neurones in the medulla oblongata
Central pattern generator is a network of communicating pathways which work to produce an appropriate respiratory rate and depth based on need
What innervates muscles of inspiration
Neurones of the dorsal respiratory group stimulate motor neurones innervating muscles of inspiration
What is the Hering Breuer reflex
Stretch receptors in the lung send impulses to the pons to switch off the stimulation and prevent overinflation of the lungs
Expiration can then occur and is generally mainly passive due to elastic recoil
For active expiration neurones in ventral respiratory group send impulses to expiratory muscles
What do the carotid and aortic bodies do and how are they innervated
Monitor PaO2, PaCO2 and arterial H+ very high blood supply
Carotid bodies innervated by cranial nerve IX aortic bodies innervated by CN X
Increase AP generation when PO2 drops - signals respiratory centre to increase ventilation
Where are the central chemoreceptors found and what do they do
Exact location uncertain
Monitor PaCO2 only
CO2 crosses the blood brain barrier and CA acts to generate HCO3- and H+
The chemoreceptors detect this H+
What is the more important factor governing respiration under normal circumstances
PaCO2 detected by chemoreceptors
PaO2 is less sensitive as HB saturation nearly 100% until PaO2 drops below 70mmHg
What results = acidosis or alkalosis
Decrease in ECF pH acidosis = less than 7.35
Increase in ECF pH alkalosis = more than 7.45
What are the three mechanisms to achieve acid:base balance
Buffering = first line
Lungs = second line
Kidneys = third line
Tiny alterations are constantly being balanced
Defects can not be completely restored by these methods
Where does H+ come from
H+ is produced from the dissociation of acids - carbonic acid from CO2 and H2O and non-volatile acids from nutrient metabolism
CO2 is there for a potential acid
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
What is respiratory acidosis and metabolic acidosis
Respiratory acidosis - accumulation of H+ due to a build up of CO2
Metabolic acidosis - accumulation of H+ due to a build up of fixed acids e.g. H2PO4
What does a buffer system do
A system which can bind or donate H+
Usually an acid also proteins and ammonia
Obey the Law of Mass action
What is a good buffer and which is the most important
A weak acid dissociates incompletely in water most of H+ stays bound H2CO3 is a weak acid and HCO3- is a strong base
The carbonic acid system is most important to buffer changes for pH other than those of respiratory origin
