SM_157a: Control of Breathing Flashcards
Brain creates _______ and modifies that rhythm
Brain creates basic breathing rhythm and modifies that rhythm
(adjusts output to variety of muscles)
The motor pattern for breathing is generated by a _______
The motor pattern for breathing is generated by a central pattern generator
What is a central pattern generator?
A neuronal circuit within the CNS that can produce a patterned motor behavior such as breathing, locomotion, vocalization, or chewing without requiring phasic sensory feedback
Phasic sensory feedback may modify the motor output but is not essential for generting the basic motor pattern
What are the two large important regions in respiratory neuroanatomy?
- Ventral respiratory column
- Retrotrapezoid column
What is the function of the ventral respiratory column?
Generating a respiratory rhythm
What is the pre-Bötzinger complex?
Inspiratory rhythm generator
Where is the pre-Bötzinger complex found?
In ventral respiratory column, caudal to facial nucleus in ventral medulla
What is the retrotrapezoid nucleus?
Central chemoreceptor
Where is the retrotrapezoid nucleus found?
Ventral to facial nucleus, very near ventral surface of medulla
What are the basic sensory feedback mechanisms for breathing?
- Pulmonary mechanoreceptors
- Chemoreceptors
What are the types of pulmonary mechanoreceptors?
- Slowly adapting pulmonary stretch receptors (PSR or SAR)
- Rapidly adapting (irritant) pulmonary stretch receptors (RAR)
- C-fibers
What are the types of chemoreceptors?
- Peripheral chemoreceptors
- Central chemoreceptors
Where are the peripheral chemoreceptors located?
- Carotid bodies
- Aortic bodies
Where are the central chemoreceptors located?
Retrotrapezoid nucleus (potentially other places in CNS as well)
Compare slowly adapting pulmonary stretch receptors to rapidly adapting pulmonary stretch receptors
- Slowly adapting receptors adapt slowly and easily to respiratory lung inflation
- Rapidly adapting receptors require higher lung inflation to be activated and adapt firing rate even if a high lung inflation is maintained
Where are slowly adapting pulmonary stretch receptors located?
Smooth muscle of trachea and bronchi
What is the size and myelination status of slowly adapting pulmonary stretch receptors?
Large, myelinated fibers
What activates slowly adapting pulmonary stretch receptors?
- Lung inflation
- Bronchoconstriction
What does activation of slowly adapting pulmonary stretch receptors cause?
- Breuer-Hering reflex: facilitates expiration, terminates inspiration if VT is elevated (e.g. exercise), prolongs expiration (slows breathing)
- Abdominal (expiratory) muscle activation: airway obstruction -> increased FRC -> slowly adapting pulmonary stretch receptor activation -> decreased f and increased activation of expiratory muscles
- Bronchodilation: negative feedback loop
What is the effect of the Breuer-Hering reflex?
- Facilitates expiration
- Terminates inspiration if VT is elevated (e.g. exercise)
- Prolongs expiration (slows breathing)
(caused by activation of slowly adapting pulmonary stretch receptors)
What is the effect of abdominal (expiratory) muscle activation after activation of slowly adapting pulmonary stretch receptors?
Airway obstruction -> increased FRC -> slowly adapting pulmonary stretch receptor activation -> decreased f and increased activation of expiratory muscles
Bronchodilation after activation of slowly adapting pulmonary stretch receptors is a _______ feedback loop
Bronchodilation after activation of slowly adapting pulmonary stretch receptors is a negative feedback loop
What stimulates rapidly adapting pulmonary stretch receptors?
- Inhaled irritants
- Rapid large inflation
- Lung deflation
Where are rapidly adapting pulmonary stretch receptors located?
In airways from the nasopharynx to the bronchi
Compare the size of rapidly adapting pulmonary stretch receptors to that of slowly adapting pulmonary stretch receptors
Rapidly adapting pulmonary stretch receptors have somewhat smaller myelinated fibers than slowly adapting pulmonary stretch receptors
How does activation of rapidly adapting pulmonary stretch receptors facilitate inspiration?
- Increased inspiratory effort (e.g. augmented breath/sigh)
- Bronchoconstriction (may contribute to bronchoconstriction triggered by histamine in asthma)
- Facilitate/produce cough/sneeze
Peripheral chemoreceptors are stimulated by _______, _______, and _______
Peripheral chemoreceptors are stimulated by decreased PaO2, increased PaCO2, and decreased pH
_______ rather than _______ appears to provide the primary stimulus for peripheral chemoreceptors
PaO2 rather than arterial O2 content appears to provide the primary stimulus for peripheral chemoreceptors
Anemia stimulates _______ more strongly than _______
Anemia stimulates aortic bodies more strongly than carotid bodies
PaO2 < ___mmHg (i.e. SaO2 < ____%) stimulates peripheral chemoreceptors
PaO2 < 60 mmHg (i.e. SaO2 < 90%) stimulates peripheral chemoreceptors
Central chemoreceptors are found ________, specifically the _______
Central chemoreceptors are found on/near ventrolateral surface of medulla, specifically the retrotrapezoid nucleus (rostral end of the ventral respiratory column in ventrolateral medulla)
Central chemoreceptors are responsive to _____ and _____ but not _____
Central chemoreceptors are responsive to increase PaCO2 or decreased pH but NOT changes in PO2
Ventilation can ____ with a ____ mmHg increase in PaCO2
Ventilation can double with a 2 mmHg increase in PaCO2
Hypoxia augments the ventilatory response to ______
Hypoxia augments the ventilatory response to hypercapnia
Hypercapnia or acidosis augments the ventilatory response to _____
Hypercapnia or acidosis augments the ventilatory response to hypoxia
____ is the most potent physiologic stimulus of breathing
CO2 is the most potent physiologic stimulus of breathing
Describe the dependence of ventilatory responses on PCO2
As alveolar PO2 increases, total ventilation increases less for a given increase in alveolar PCO2
Describe the dependence of ventilatory responses on PO2
As alveolar PCO2 decreases, ventilation decreases less for a given increase in alveolar PO2
