Phys - Control of breathing Flashcards
Where does involuntary control of breathing happen in brain?
Pons and medulla (brainstem)
Three brainstem neuron groups involved in breathing
- Medullary respiratory center
- Apneustic center (pons)
- Pneumotaxic center (pons)
Two divisions of medullary respiratory center and their functions
- Inspiratory center - controls rate of breathing by setting frequency
- Expiratory center - usually a passive process so really only active during exercise
How do chemoreceptors relay info to inspiratory center?
CN 9 and 10
How does inspiratory center relay motor output to diaphragm?
Phrenic N
What does the apneustic center do?
Prolong inspiration by exciting inspiratory center
What does pneumotaxic center do?
Regulates respiratory rate; inhibits inspiratory center so decrease rate
Describe how breathing rate is set by inspiratory center.
Rhythm-generating neurons have short bursts of AP that suddenly stop; corresponds with diaphragmatic contraction followed by quiescence
Three central inputs to medulla
- Cerebrum
- Apneustic center
- Pneumotaxic center
5 peripheral inputs to medulla
- Pulmonary stretch receptors
- Baroreceptors
- Gamma receptors
- Respiratory muscles
- Carotid and aortic bodies (chemoreceptors)
What do gamma receptors do?
They’re in muscle and sense PO2 to determine whether muscle moved
Normal PO2
95
Normal PCO2
40
Normal pH
7.4
Two divisions of chemoreceptors
Central and peripheral
Goal of central chemoreceptors
Short-term regulation of arterial gases by responding to changes in PaCO2
BBB is impermeable to ____ and permeable to ____
HCO3- and H+
CO2
If BBB is impermeable to H+, how do H+-sensitive chemoreceptors sense a change in pH?
CO2 diffuses into CSF and forms H+ and HCO3-
Reduced pH sensed by central chemoreceptors has what effect on respiratory rate?
Increase (blow off more CO2)
What does the HCO3- formed in the CSF do?
Diffuses across BBB via an unknown transporter to whichever side has a lower pH
Receptors in aortic body vs. carotid body
Aortic = O2 and CO2 only Carotid = O2, CO2, and H+
How do peripheral chemoreceptors send info to medulla?
CN 9 and 10
When do O2 chemoreceptors stimulate medulla?
At PaO2<60 mmHg
remember this is when O2-Hb curve becomes steep
What role do CO2 chemoreceptors play?
Not as important as central H+ chemoreceptors or peripheral O2 chemoreceptors