SM 157a - Control of Breathing Flashcards
The PreBötC signals to the _________________, in order to generate [inspiration/expiration]
The PreBötC signals to the inspiratory bulbospinal neurons in the rostral ventral respiratory column** , in order to generate **inspiration
What is the difference between the Breur-Hering inspiratory terminating reflex and the Breur-Hering expieratory facilitating reflex?
They are two parts of the same reflex
- Inspiratory terminating reflex
- Activated when lung inflation is 3*VT
- Terminates current inspiration and initiates expiration
- Expiratory facilitating reflex
- Activated when lung inflation is prolonged
- Slows breathing
- Prolongs expiration
- Activates abdominal expiratory muscles
If the body’s response to increases in PaCO2 is to hyperventilate, why do patients with chronic respiratory insufficiency hypoventilate?
The body adapts to chronically elevated PaCO2
- Compensatory increases in arterial [HCO3-] lead to increased [HCO3-] in the brain
- This resets medullary (central) chemoreceptors, leading to decreased respiratory drive
- The body basicallly becomes more okay with chronic high levels of PaCO2
The parafacial respiratory group signals to the _________________, in order to generate [inspiration/expiration]
The parfacial respiratory group signals to the expiratory bulbospinal neurons in the caudal ventral respiratory column** , in order to generate **expiration
A sigh or augmented breath is a reflex caused by activation of the ____________ pulmonary stretch receptors
A sigh or augmented breath is a reflex caused by activation of the rapidly adapting pulmonary stretch receptors
Peripheral chemoreceptors begin to really respond to hypoxemia when PaO2 decreases below _____ mmHg
Peripheral chemoreceptors begin to really respond to hypoxemia when PaO2 decreases below 60 mmHg
What stimulus activates the slowly adapting pulmonary stretch receptors?
What is their response?
The slowly adapting pulmonary stretch receptors are activated by lung inflation or bronchoconstriction
They will continue rapid firing as long as inflation is maintained
They function to terminate the current inspiration and initiate expiration
Which pathophysiologic stimulus will most strongly activate the body’s ventilatory response?
- Increased PaCO2
- Decreased pH
- Decreased PaO2
a. Increased PaCO2
What does the pre Bötzinger complex (preBötC) do?
Where is it located?
The preBötC is responsible for generating inspiratory breathing rhythm
It is located in the rostral ventral respiratory column (VRC), which is located in the ventrolateral medulla
Describe the ventilatory response to increased PaCO2
Increased PaCO2 causes…
-
Central and peripheral chemoreceptor activation
- Central chemoreceptors have the strongest response
-
Increase alveolar ventilation by increasing minute ventilation (V̇E)
- There is a linear increase in V̇E as PaCO2 increases
- Steeper slope = more sensitive chemoreceptor
Most of the response to short-term decreases in pHa can be attributed to which receptors?
Peripheral chemoreceptors
Describe the body’s compensatory response to chronically elevated PaCO2
Chronically elevated PaCO2 causes…
- Compensatory increase in arterial [HCO3-] over days
- Due to increase in kidney retention of HCO3-
- Eventually, the brain [HCO3-] will increase
- This resets medullary (central) chemoreceptors
- Increased [HCO3-] in the brain decreases respiratory drive
- CO2 sensitivity is reduced
- The slope of the V̇E/PaCO2 curve decreases
- This resets medullary (central) chemoreceptors
Describe the central chemoreceptor response to lactic acidosis
The central chemoreceptors are not very good at responding to changes in pH; H+ ions don’t typically cross the blood-brain barrier
However, the central chemoreceptors are very responsive to high PaCO2 - they trigger a ventilatory response
Activation of c-fibers + rapidly adapting receptors results in a [cough/sneeze]
Activation of c-fibers + rapidly adapting receptors results in a cough
Why is V̇A/Q̇ higher in the apical regions of the lung than the basal regions (in an upright person)?
The apex of the lung has a lower compliance (-> lower V̇) and lower blood flow (Q̇) than the base.
However, the decreased compliance, and therefore decreased V̇, is less than the decrease in blood flow.
This means that V̇A/Q̇ will be higher in the apex of the lung than the base, if a person is sitting upright
Where are the slowly adapting pulmonary stretch receptors located?
Airway smooth muscle
Which pontomedullary cardiorespiratory cell group contains teh central pattern generator for expiration?
The parafacial respiratory group