Lecture 5C Flashcards
Breathing is an involuntary process? What parts of the brainstem controls it
Yes. The medulla and pons ultimately control breathing
What three groups of neurons or brainstem centers regulate breathing
Medullary Respiratory Center
Apneustic Center
Pneumotaxic Center
What two groups are found within the Medullary Respiratory Center?
Dorsal Respiratory group (DRG)
Ventral Respiratory group (VRG)
What is the DRG responsible for?
Primarily responsible for inspiration and generates the basic rhythm for breathing
What two cranial nerves give input to the DRG and what kind of information does each give?
CN X –> peripheral chemoreceptors and mechanoreceptors
CN IX–> Peripheral chemoreceptors
Output from the DRG travels how and where?
Via the phrenic nerve to the diaphragm and external intercostals
What is VRG responsible for?
Primarily responsible for expiration
When is the VRG active?
When expiration becomes an active process, Like during exercise. It is not active during normal, quiet breathing when expiration is passive
What muscles contract when DRG is active?
Diaphragm and External intercostals actively contract. Normal INSPIRATION
Where is the Apneustic Center located in the brainstem?
In the lower pons
What is the role of Apneustic Center?
Stimulates inspiration, producing deep and prolonged inspiratory gasps (apneusis), followed by occasional brief exhalations
Explain the mode by which the Apneustic center functions
Stimulations of these neurons apparently excites the inspiratory center in the medulla, prolonging the period of action potentials in the phrenic nerve, and thereby prolonging the contraction of the diaphragm
Where is the Pneumotaxic center located?
In the upper pons
What is the role of Pneumotaxic center?
- Inhibits inspiration and limits the burst of action potentials in the phrenic nerve
- Does this by limiting the size of the Tidal volume
Does the Cerebral cortex have a role in Breath?
Yes it can temporarily override the brainstem centers. For example, a person can voluntarily hyperventilate.
What happens to the pressures in hyperventilation?
Decrease in PaCO2, which causes arterial pH to increase. Hyperventilation is self-limiting because the decrease in PaCO2 will produce unconsciousness and person will revert to a normal breathing pattern
Can a person hypoventilate?
Yes but it is difficult. This causes a decrease in PaO2 and an increase in PaCO2 both of which are strong drives for ventilation.
Where are the central chemoreceptors found?
Bilaterally in the ventrolateral medulla
Where are the peripheral chemoreceptors found?
In the aortic arch and carotid arteries
Which chemical influencing respiration is the most potent and most closely controlled
CO2
What is the normal arterial Pco2
40 mmHg with a +- 3 mmHg
A decrease in pH of the CSF produces what?
Increase in breathing rate (hyperventilation)
Does H+ cross the BBB?
Not as well as CO2 does
Why does Co2 diffuse from arterial blood into the CSF?
it is lipid-soluble and readily crosses the BBB
