Control of Breathing Flashcards
What system controls the contraction-relaxation of the diaphragm and intercostals
central nervous system - they are striated and have no intrinsic or tonic activity
Are respiratory pump muscles automatic or autonomic?
automatic - breathing occurs without interruption up to a point
Where is breathing rhythm generated?
the brainstem
What breathing region is located in the nucleus of the solitary tract? (NTS)
the dorsal respiratory group (DRG) - dorsomedial medulla, caudally to mid-rostral
Which breathing apparatus is a continuous column in the ventrolateral medulla?
the ventral respiratory column
What group contains both the parabrachial complex, the Kolliker Fuse nucleus, and is in the rostral dorsolateral pons?
pontine respiratory group
Where are the neurons responsible for breathing rhythm GENERATION?
the VRC - pre Botzinger complex
What neurons MIGHT be responsible for expiratory rhythms?
the parafacial respiratory group (pFRG)
From the preBotC and pFRG, whre does the activity get relayed most immediately?
pre motor neurons
Slowly adapting pulmonary stretch receptors are in what 3 classes of sensors?
pulmonary mechanoreceptors
What are the 3 sub types of pulmonary mechanoreceptors?
slowly adapting stretch
rapidly adapting (irritant)
c fibers
What effect do arterial baroreceptors have on ventilation?
inhibitory
Where are slowly adapting pulmonary stretch receptors located?
airway smooth muscle
how are slowly adapting pulmonary stretch receptors activated?
lung inflation or bronchoconstriction
When is PSR input to the brainstem sufficiently strong to terminate ongoing inspiration and initiate expiration? What is this reflex called?
When lung inflation is 3x normal tidal volume (i.e. during exercise).
Breuer Hering inspiratory terminating reflex
If lung inflation is maintained into the expiratory period due to obstruction, what happens to experation length and muscle activation? What is this called?
expiration is prolonged, decreasing RR, and muscles are activated
Breuer Hering expiratory facilitating reflex
Rapidly adapting pulmonary stretch receptors (RAR) also go by what name?
irritant
Where are RAR located?
between airway epithelial cells in trachea and larger bronchi
RAR activation facilitates what part of breath?
inspiration (i.e. sigh or augmented breath)
What 3 things other than inspiration do RAR most likely contribute to?
- cough reflex
- mucus production
- bronchoconstriction
In the epipharynx, what does RAR activation initiate?
the aspiratory reflex
What do C fibers sense?
accumulation of edema and inhaled irritants
Where are C fibers? Are they myelinated?
close to the alveoli
unmyelinated
What breathing patterns and sensations are C fibers involved in?
rapid shallow breathing patterns of pulmonary disease
dyspnea
What typically triggers coughing?
irritating stimulus in or below oropharynx
What typically triggers sneezing?
irritation above oropharynx
Where is sneezing stimulated?
Sneezing is stimulated via receptors in the mucous membrane of nose with axons in branches of the trigeminal nerve.
Where is coughing generated?
Coughing is generally attributed to activation of c-fibers with a permissive role from rapidly adapting receptors.
What are carotid and aortic bodies?
peripheral chemoreceptors stimulated by decreasing PaO2, increasing PaCO@ and decreasing pHa
When do peripheral chemoreceptors respond to hypoxemia?
when PaO2 is below 60 mmHg, very rapidly below 50 mmHg due to Hb-O2 dissociation curve
What is an important subset of central chemoreceptors?
retrotrapezoid nucleus in the medulla
Which receptors respond most strongly to changes in PaO2? PaCO2?
peripheral = 02 central = CO@
Why are central chemoreceptors not receptive to changes in pH?
H+ doesn’t cross the BBB
Activation of which chemoreceptors is responsible for the changes in alveolar ventilation with increasing CO2?
central chemoreceptors (70%)
What occurs with chronic changes to PaCO2?
arterial increase in bicarb
slow central response to this which resets medullary chemoreceptors and decreases respiratory drive
What happens to CO2 sensitivity in chronic changes to PaCO2?
it is reduced (slope of alveolar ventilation v. PaCO2)
What is Cheyne-stokes breathing?
decreased central chemoreceptor sensitivity causes decreased CO and a delay in responding to changes in PACo2
i.e. apnea
What is congenital central hypoventilation syndrome?
CCHS is a potentially life-threatening genetic disorder characterized by hypoventilation especially during sleep due to an impaired ventilatory response to PCO2 and PO2. Additionally, the disease is often associated with functional impairments of the autonomic nervous system and tumors of neural crest derivatives
What is the defining mutation of CCHS?
polyalanine expansion in Phox2b geen
What does the polyalanine mutation in CCHS cause in the central chemoreceptors?
absence of retrotrapezoid neurons causes a loss in normal respiratory drive from chemoreceptors
What is Rett syndrome
a developmental disorder of the CNS that is caused by mutations in Xlinked Mecp2
Rett syndrome is X linked, is it more common in boys or girls?
girls!
Cheyne-stokes breathing is usually seen in which genetic condition?
Rett syndrome
Match the following pontomedullary cardiorespiratory cell groups with the descriptions that follow. a) parafacial respiratory group
b) preBötzinger complex
c) rostral ventral respiratory group d) caudal ventral respiratory group e) dorsal respiratory group
f) pontine respiratory group
g) retrotrapezoid nucleus
1) Contains the central pattern generator for inspiration.
2) Hypothesized to contain the central pattern generator for expiration.
3) Collection of respiratory neurons located in the nucleus of the solitary tract.
4) A site of central chemoreception
5) Important for the coordination of respiratory control with activity in other systems. 6) Principal site of inspiratory bulbospinal premotor neurons.
7) Principal site of expiratory bulbospinal premotor neurons.
1) b, 2) a, 3) e, 4) g, 5) f, 6) c, 7) d
Match the following sensory receptors to the reflex effects that follow. a) slowly adapting pulmonary stretch receptors (SARs).
b) rapidly adapting pulmonary stretch receptors (RARs).
c) bronchopulmonary C-fibers.
8) Breuer-Hering reflex termination of an ongoing inspiration 9) Sigh or augmented breath
10) Breuer-Hering reflex facilitation of expiration
11) Shallow rapid breathing
8) a, 9) b 10 a, 11) c
Given the fact that tubercle bacilli grow better at higher oxygen tensions, in what region of the lungs would you expect tuberculosis to begin? Why?
Tubercle bacilli will prefer the apices of the lung, since the partial pressure of O2 is highest there due to the normal distribution of V & Q in upright humans in a gravitational field. Which parts of the lungs of cows and bats (which hang upside down a lot) would you expect to find tubercle bacilli?
Why does inhomogeneity of ventilation and perfusion produce hypoxemia but not hypercapnia?
The relationship between gas content and partial pressure is relatively linear for CO2, so that if one region is relatively under ventilated, it can be compensated for by another region that is relatively over ventilated. However, for O2, the relationship between gas content and partial pressure is quite non-linear and arterial blood is on the flat portion (Hb is nearly saturated) of the Hb-O2 dissociation curve. This means that increasing the partial pressure of O2 (by increasing the ventilation) of the lung will only slightly increase the oxygen content. In contrast, a precipitous reduction in O2 content results from under ventilation due to the steep decrease in Hb-O2 binding at lower O2 pressures.
Why is VA/Q higher in the apical regions of the lung in an upright person than it is in the basal regions?
In the upright lung in a gravitational field, the apex of the lung has both a lower compliance (and hence lower ventilation) and lower blood flow than the base. Nevertheless, VA Q is higher in the apex because the decrease in compliance, and hence ventilation, is less than the decrease in blood flow
Of the following, which one is responsible for rapid shallow breathing?
SARs
RARs
C fibers
C fibers
Of the following which one is responsible for the Breuer Hering reflex facilitation of expiration?
SARs
RARs
C fibers
SARs
Of the following, which one is responsible for sigh’s or augmented breaths?
SARs
RARs
C fibers
RARs
Of the following, which one is responsible for the Breuer-Hering reflex termination of an ongoing inspiration?
SARs
RARs
C fibers
SARs
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Which one contains the central pattern generator for inspiration?
the prebotzinger complex
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Of these, which ones contains the central pattern generator for expiration?
parafacial respiratory group
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
of these, which one is a collection of respiratory neurons in the nucleus of the solitary tract?
dorsal respiratory group
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Of these, which one is a site of central chemoreception?
retrotrapezoid nucleus
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Of these, which one is important in coordinating respiratory control with other systems?
pontine respiratory group
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Of these which one is the primary site for inspiratory bulbospinal premotor neurons?
rostral ventral respiratory group
Parafacial respiratory group pre Botz complex rostral ventral respiratory group caudal ventral respiratory group dorsal respiratory group pontine respiratory group retrotrapezoid nucleus
Of these, which one is the principal site of expiratory bulbospinal premotor neurons?
caudal ventral respiratory group
How would you calculate VCO2 if the FeCO2 is 0.04, the Ve is 5.51, the PaCO2 is 40 mmHg, and the barometric pressure is 761 mm Hg? What about Va?
VCO2 = FeCO2 X Ve
VA = RTVCO2/PaCO2
