Control of Ventilation Flashcards
What is Dyspnea
Sensation of shortness of breath
What do the Pons respiratory centres do
Influence and modify activity of the medullary centres to smooth out transitions between inspiration and expiration
What does the Apneustic centre of the pons respiratory centre do
Sends signal to the Dorsal Respiratory Group (DRG) in the medulla to delay the inspiratory cut off from the pneumotaxic centre and vagus, it excites the inspiratory centres
What does the Pneumotaxic centre of the pons respiratory centre do
Acts as “off switch” neurons for inspiration. Stimulation of this centre terminates inspiration earlier to reduce tidal volume and cause higher respiratory frequency
What is the Dorsal Respiratory Group (DRG) also known as
The inspiratory centre
Where is the DRG located
Located near the root of the cranial nerve IX (glossopharyngeal) in the dorsomedial medulla (ventrolateral nucleus)
What does the DRG do
Excites the inspiratory muscles includes the diaphragm, external intercostals and the Ventral Respiratory Group (VRG) neurons
What inputs does the DRG receive
Pretty much all peripheral afferents (chemo., mechanism., proprio.) via the vagus and glossopharyngeal nerves
Apneustic centre
What do the inspiratory neurons of the Ventral Respiratory Group (VRG) activate
Accessory muscles of inspiration and external intercostals
What do the expiratory neurons of the Ventral Respiratory Group (VRG) activate
Internal intercostals and abdominal muscles
When are the expiratory neurons of the VRG active
Only during exercise but not during normal breathing
Where are the DRG and VRG located
In the Medulla Oblongata
What factor is the main driving force for breathing
PaCO2
Why are chemoreceptors more sensitive to CO2 than O2
Oxygen content of the blood decreases more slowly due to the large reservoir of oxygen attached to haemoglobin
What is the role of chemoreceptors
They provide the input to modify the rate and depth of breathing to maintain arterial PaCO2 at 40mmHg
What are the 2 kinds of chemoreceptor
Central
Peripheral
What are central chemoreceptors responsive to and what do they use to carry out their role
- responsive to increased arterial PaCO2
- Act by way of CSF [H+]
What are peripheral chemoreceptors responsive to
- Decreased arterial PaO2
- Increased arterial PaCO2
- Increased [H+]
Where are the central chemoreceptors located
0.2mm below the anterolateral surfaces of the medulla, close to the origins of the glossopharyngeal and vagus nerve
If PaCO2 increases what happens to the ventilation
It increases
What do the central chemoreceptors respond to
pH of the CSF.
How is carbonic acid formed in the CSF
CO2 combines with water to form carbonic acid that dissociates to form Hydrogen ions and bicarbonate
What body structure receives more blood flow than any other organ
The peripheral chemoreceptors
2000ml/100g/min
Despite the very high metabolic rate of the peripheral chemoreceptors, what keeps the capillary PO2 and PCO2 close to arterial values
the mad blood flow
