PHYS: Control of Breathing Flashcards
Where is the central respiratory control center located?
Medulla
The central respiratory control center is made up of synaptic connections among what three entities?
1) PreBotzinger complex
2) Ventral respiratory group
3) Dorsal respiratory group
Which of the portions of the central respiratory control center is responsible for rhythm generation?
TRICK QUESTION!
Though the PreBotzinger complex is the main entity responsible for rhythm generation, the VRG and DRG also may have a rhythm of their own.
What is the main role of the ventral respiratory group?
output to motor neurons
What is the main role of the dorsal respiratory group?
receives peripheral inputs and modulates the VRG
What are the two collections of cells in the pons that affect the activities of the medullary center?
1) Apneustic center (lower pons)
2) Pneumotaxic center (upper pons)
What does the apneustic center of the pons do, and how does it do it?
Prolongs inspiration via affecting the excitability of medullary respiratory control nerve circuits
What does the pneumotaxic center of the pons do, and how does it do it?
regulates respiratory rate (change the length of inspiration) by inhibiting the medullary inspiratory neurons
What is the Hering Breur Reflex?
Negative feedback mechanism where inflation of the lungs inhibits inspiration
How does the Hering Breur Reflex input into the respiratory control center?
via vagal fibers from pulmonary stretch receptors
List the two baroreceptors that influence the respiratory control center?
carotid sinus
aortic baroreceptors
How do baroreceptors work?
decreases in blood pressure increase ventilation
What is the gamma-efferent input (muscle spindle system)?
signal to suspend inspiration and start expiration due to changes in lung compliance and airway resistance (ex. when your snorkel fills with water, you immediately blow out)
What do irritant airway receptors do?
they cough in response to irritants (vagus nerve)
What do juxtacapillary (J) receptors cause? Why?
The cause shallow, rapid breathing due to increased restriction to ventilation
What controls conscious (voluntary) breathing?
cerebral cortex
What do central chemoreceptors respond to (predominant minute to minute alveolar ventilation regulator)?
PaCO2 (pH changes of CHF)
The partial pressure of carbon dioxide in arteries can be calculated by what equation?
production of CO2/alveolar ventilation
Which has a more variable pH: Extracellular fluid in the brain or capillary blood?
capillary blood
How does CO2 alter the pH of the brain?
1) it diffuses across the BBB
2) it undergoes the reaction into H+ and bicarbonate
3) H+ ions stimulate H+ sensitive neurons
4) these chemotaxic neurons tell the respiratory control center to increase inspiration (blow off CO2, increase pH)
How does the bicarbonate leave the brain (eventually–when it is resetting)?
Bicarbonate-Cl-exchanger
What happens to CO2 if you have severe ventilatory difficulty?
PaCO2 will increase, decreasing the pH of the medulla and increasing the respiratory drive
How does the CSF pH reset in the brain?
after a while of increased respiratory drive, the bicarbonate in the brain will cross across the BBB which increases the brain pH and will inhibit the respiratory drive. Overall, the PaCO2 will stay increased and the pH of the CSF will be more acidic than body pH
How do the carotid bodies work?
they signal Oxygen decreases, and their O2 sensitive potassium channels will be inhibited (depolarizing the cell, increasing cell excitability, and stimulating the glossopharyngeal nerves)–> increase respirations
Do carotid bodies respond to O2 content of the blood or arterial partial pressure?
arterial partial pressure of oxygen
Why is it a bad idea to give a hypoxic person 100% oxygen if they have been hypoxic/unconscious for a while (drug overdose)?
Their central chemoreceptors have reset, but are not responding, so the only thing keeping their respirations going are the peripheral chemoreceptors (which sense oxygen decreases). If you suddenly give them 100% oxygen, they will stop breathing!
What is the Kussmaul respiration?
decreased insulin leads to increased fat breakdown and increased plasma fatty acids, so the body compensates by deep, rapid breathing to “blow off CO2” and return the pH from acidic to normal
