Ch 41 Regulation of respiration Flashcards
What is the function of the dorsal respiratory group?
In the nucleus tractus solaris, the termination of the Vagus and glossopharyngeal nerves.
Controls inspiration and resp rhythm.
What is meant by this statement? “The inspiratory signal is a ramp signal”
The signal for inspiration to the diaphragm starts out weak and increases in strength for 2 seconds, then ceases abruptly.
This allows the lungs to steadily fill, not inspire as sudden gasps!
What qualities of the inspiratory ramp are controlled?
- Rate of increase of the ramp signal (usually utilized only in heavy respiration)
- The limiting point at which the ramp suddenly ceases (used in normal respiration)
Where is the pneumotaxic center and what is its function?
Where: nucleus parabrachialis
Function: Controls the switch-off of the inspiratory ramp to control duration of the lung-filling phase. Inhibitory to the dorsal resp group
Can also increase the rate of breathing, secondarily.
Where is the ventral respiratory group and what are its functions?
Where: Anterior and lateral to the dorsal resp group
What: mostly inactive during normal breathing. When resp drive increases, signals spill over to this group and …
-A few neurons stimulated = inspiration
-Other neurons stimulated = expiration control
Basically, extra oomph
What is the Hering-Breuer Inflation Reflex?
Stretch receptors in the muscular walls of bronchi and bronchioles send signals via the Vagus to the Dorsal resp group when the lungs are overstretched.
Action: Signals from these stretch receptors shut off inspiration to protect lung tissue
Which ions have direct effects on the respiratory centers?
H+ and CO2 in the blood acti directly on the resp center. Oxygen has an indirect effect by action on PERIPHERAL chemoreceptors
Where are the peripheral chemoreceptors? What cranial nerves are associated with each set of receptors?
Carotid and aortic bodies.
Carotid: bilaterally in the bifurcation of the common carotids. Goes to glossopharyngeal
Aortic bodies: along the arch of the aorta. Goes to the vagus
Where is the chemosensitive area?
Just beneath the ventral surface of the medulla
How does blood CO2 indirectly but strongly affect the thermosensitive area?
Increased blood CO2 = increased CSF and interstitial fluid CO2.
CO2 reacts with water there to form H+, which strongly stimulates the resp chemosensitive area
Why is the effect of blood CO2 on controlling respiratory drive only potent acutely, but weak in a chronic state?
- Kidneys readjust blood H+ toward normal by increasing blood bicarbonate
- ***Bicarbonate ions diffuse through the blood-brain and blood-CSF barriers to combine with H+ and bring it back to normal
In what range of CO2 does CO2 exert powerful effects on alveolar ventilation?
In the normal range of blood PCO2, it has a strong effect. But a weak effect with blood pH is actually within normal range
What excites the peripheral chemoreceptors?
Decreased arterial oxygen, increased CO2 and H+
How is the response to peripheral chemoreceptors sensing increased CO2 or H+ different from when the central chemoreceptors perceive it?
Central: more marked response, more power effect on the receptors
Peripheral: 5x as rapid of a response
Briefly, how does altitude acclimatization occur?
In 2-3 days, the resp center of the brain loses a lot of sensitivity to CO2, so resp system switches for trying to constantly blow off CO2, to trying to increase alveolar ventilation and increase oxygen supply via ventilation
What is the basic mechanism of Cheynes-Stokes breathing?
- Overbreathing leads to too much CO2 getting blown off from pulmonary blood and blood O2 is increased
- It takes several seconds for the altered pulmonary blood to reach the brain and signal a change in respiration
- By this time, the overbreathing has gone on longer
- Brain resp center is excessively depressed
- Opposite cycle begins, so CO2 increases and O2 drops.
Occurs when: severe cardiac failure, brain damage causing increased negative feedback gain
How does brain edema affect respiration?
Trauma makes tissue swell from edema, compresses blood vessels, and therefore blocks the “highways” carrying “signals” that would control respiration
How does cyanide poisoning impair oxygen usage?
Cytochrome oxidase is blocked completely, so tissues are unable to use oxygen at all
How does Vitamin B deficiency lead to oxygen deprivation?
‘Beriberi’ : several steps in O2 utilization are blocked and formation of CO2 is compromised
In which type of hypoxia would oxygen therapy be marginally but still beneficial?
If caused by anemia, abnormal hemoglobin transport of O2, circulatory deficiency, or physiologic shunt, O2 is less valuable but could still be the difference between life and death
In what type of hypoxia is oxygen therapy of little use?
Inadequate tissue use of oxygen
At what concentration of hemoglobin does blood appear cyanotic?
When arterial blood contains less than 5 grams of Hb per 100ml blood. This is why anemics don’t appear cyanotic
