EXAM III: 5C Regulation of Respiration Flashcards
What is the role of the Brainstem is breathing?
- Breathing is an involuntary process that is controlled bny the medulla and pons.
- The frequency of normal involuntary breathing is regulated by 3 groups of neurons or brainstem centers
How is volume of air inspired and expired controlled?
- Tightly controlled both with respect to frequency of breaths and to tidal volume
- Breathing is regulated so lungs can maintain the Pa O2 and Pa CO2 within their normal ranges, even under widely varying conditions such as exercise.
What are the 3 neurons or brainstem centers that regulate breathing?
1) Medullary respiratory center
2) apneustic center
3) pneumotaxis center
In the Medullary Respiratory (Rhythmicity ) center what is primarily responsible for inspiration and generates the basic rhythm for breathing?
Dorsal Respiratory Group (DRG)
What 2 brainstem centers are located in the Pons?
- Pneumotaxic center
2. Apneustic center
What is the difference between DRG and VRG and where are they located?
DRG–> in the MEDULLA, to inspiratory muscles (Diaphragm and external intercostals)
VRG–> in the MEDULLA, to expiratory muscles (internal intercostal and others)
What is role of CN X in DRG?
Inputs information from peripheral chemoreceptors and mechanorecepts (e.g ling stretch receptors, irritant receptors, J receptors and joint & muscle receptors)
What is role of CN IX in DRG?
- Inputs information from peripheral chemoreceptors
- Output from the DRG travels via the phrenic nerve to the diaphragm & external intercostals
What is the role of VRG? when is it activated?
- Responsible for expiration
- Not active during normal, quite breathing, when expiration is passive
- Is activated (during exercise) when expiration becomes an active process
When happens when the Dorsal Respiratory group is ACTIVE ?
2 seconds–> Diaphragm & external intercostals actively contract–>normal inspiration
When happens when the Dorsal Respiratory group is INACTIVE ?
3 seconds–>Diaphragm & external intercostals relax followed by elastic recoil of the lungs–>Normal expiration
Where is the Apneustic center located? When is it stimulated?
- Located in the lower Pons
- Stimulates inspiration, producing deep & prolonged inspiratory gasps (apneusis) followed by occasional brief exhalations
-Stimulation of these neurons excites inspiratory center in medulla, and prolonging the contraction of the diaphragm.
Where is the Pneumotaxic center located and what does it inhibit ?
- Located in the upper pons
- inhibits inspiration and limits the burst of APs in the phrenic nerve
- limits the size of the TV
What is the Role of the Cerebral Cortex?
Commands of cerebral cortex can temporally override the brainstem centers
Example: person can voluntarily hold breath(increase CO2 and decrease O2) or hyperventilate (decrease CO2 and increase O2)
Where are the central chemoreceptors and peripheral chemoreceptors located?
- Central chemoreceptors located bilateral in the ventrolateral medulla.
- Peripheral chemoreceptors are in the aortic arch & carotid arteries
How is pH, PCo2, and pH affected in the central chemoreceptors and peripheral chemoreceptors ?
In Central: pH is DECREASED and PCO2 increased
In Peripheral: PO2 ( if < 60 mm Hg) is decreased, PCO2 is increased, and pH is DECREASED
What is the most potent and most closely controlled chemicals influencing respiration?
What is the Normal arterial number for this chemical?
CO2
-Normally arterial PCo2 is 40 mmHg and maintained within +- 3 mmHg
What are the central chemoreceptors of the medulla sensitive to?
-Sensitive to the pH of the CSF–>decreased in pH i=of the CSF produces an increase in breathing rate (hyperventilation)
-H+ does not cross BBB like CO2 does.
-CO2 diffuses from arterial blood into CSF b/c it is lipid-soluble.
-In the CSF, CO2 combines w/ H2O to produce H+ &
\HCO3—>resulting H+ acts directly on the central chemoreceptors
What does an increase in PCo2 and H+ stimulate?
Breathing and decreased PCo2 & H+ inhibit breathing –>The reyslting hyperventilation or hypoventilation then returns the arterial PCO2 toward normal
What is the influence of PO2?
- The peripheral chemoreceptors are sensitive to arterial O2
- Under normal conditions , the effect of declining PO2 on ventilation is slight & mostly limited to enhancing the sensory of peripheral receptors to increased PCO2.
How does a decreased arterial PO2 affect the peripheral chemoreceptors ?
It stimulates the perip chemoreceptors and increases breathing rate–>PO2 MUST DECREASE to <60 mmHg before breathing is stumulated
-When its less than 60, breathing rate is sensitive to PO2
How does a increased arterial PO2 affect the peripheral chemoreceptors ?
Stimulates peripheral chemoreceptors and increases breathing rate.
***However the response of the peripheral chemoreceptors to CO2 is less important then the response of the central chemoreceptors to CO2 (or H+)
How does a increased arterial H+ affect the peripheral chemoreceptors ?
Stimulates them directly, independent of changes in PCO2.
How is arterial P CO2 affected with people who retain CO2 because of emphysema and chronic bronchitis?
Arterial P Co2 is chronically elevated and as a result chemoreceptors adapt to this chemical stimulus.
