Exam 3: Control Of Respiration Flashcards
What is neurogenesis?
The growth and development of nervous tissue
neurogenesis of respiratory drive is largely where?
The brain medulla but influenced by other areas and some peripheral factors
neurons of the brain send impulses down the spinal cord to where?
Lower motor neurons which innervate the muscles
What consists of neuron “pools” mostly in the
upper medulla oblongata, with some additional neurons in the
pons?
Respiratory control center
What neuronal grouping receives information from chemoreceptors, baroreceptors and lung stretch receptors?
Dorsal respiratory group
Where do afferent/sensory signals from vagus and glossopharyngeal enter the respiratory control center?
Dorsal respiratory group
What is the main driver of respiratory control?
Dorsal respiratory group
Where is the dorsal respiratory group located?
Tractus solitarius
The dorsal respiratory group contains what kind of neurons?
Inspiratory neurons
Ventral Respiratory Group contains what kind of neurons?
Inspiratory and expiratory
Where is the pneumotaxic center located?
In the upper pons, within the nucleus parabrachialis
What neuronal grouping of the respiratory control center is wired into the inspiratory neurons of the ventral and dorsal respiratory groups?
Pneumotaxic center
Where is the chemosensitive area located?
At the ventral surface of the medulla
Neurons of what respiratory control center grouping are responsive to chemistry of CSF?
Chemosensitive are
What neuronal grouping of the respiratory control center is wired into the inspiratory neurons of the dorsal respiratory groups?
Chemosensitive area
the many inspiratory neurons of the
dorsal respiratory group display rhythm signals called what?
inspiratory ramp signal
The inspiratory neurons of the dorsal respiratory group primarily send signals where?
The diaphragm
NOTE: normal, restful breathing almost entirely an inspiratory/diaphragmatic
phenomenon (with expiration a passive recoil process)
An increase in inspiratory ramp signal would result in what?
Increased contraction of the diaphragm
the pontine pneumotaxic center inhibits the inspiratory neurons (mostly of dorsal respiratory
group) in order to affect breathing how?
limit the depth of breathing
Increased pneumotaxic action will results in what?
Short inspiration (i.e. rapid breathing)
Decreased pneumotaxic action will results in what?
Lengthened inspiration as seen in restful breathing
The magnitude of the ramp signal can be modified/increased by the action of what medullary neuronal grouping?
Ventral respiratory group
How does the ventral respiratory group increase ramp signal to make breathing more powerful?
It has both inspiratory and expiratory neurons that recruit muscles of the ribcage to assist in inspiration and expiration
How does the ventilation cycle get voluntarily overridden by “higher center” of the brain?
by way of corticospinal and corticobulbar tracts directly to lower
motor neurons of thoracic musculature, bypassing respiratory control center
How does the ventilation cycle get modified by pulmonary stretch (i.e. volume) receptors in the smooth muscle of airway?
pulmonary stretch receptors in the airways (smooth muscle)
send signals up the vagi (CN X) into the dorsal respiratory group to decrease activity of inspiratory neurons
What is the Hering Breuer reflex?
is a reflex triggered to prevent over-inflation of the lung. Pulmonary stretch receptors present in the smooth muscle of the airways respond to excessive stretching of the lung during large inspirations
What is the main control input from central and peripheral receptors?
central chemoreceptor in the form of the “chemosensitive area”
on the ventral surface of the medulla
What is the primary purpose of the central chemoreceptor in the form of the “chemosensitive area”
on the ventral surface of the medulla?
to regulate the
amount of O2 and CO2 in the body
The chemosensitive area on the ventral surface of the medulla is particularly sensitive to what?
H+ (↓ pH, and indirectly to ↑ CO2)
Why is the chemosensitive area on the ventral surface of the medulla INDIRECTLY sensitive to carbon dioxide?
Because it is sensitive to H+ which is derived from the carbonic acid reaction that converts carbon dioxide and water to carbonic acid and ultimately dissociates to bicarbonate and H+
What is tachypnea?
Increased ventilation depth and rate
What do the central chemoreceptors in the form of the “chemosensitive area”
on the ventral surface of the medulla stimulate?
The dorsal respiratory group to increased ventilation rate and depth
Why do small changes in the partial pressure of carbon dioxide cause significant changes in pH that affect the neurons of the central chemoreceptors?
because there is no hemoglobin or conventional buffers in the CSF to stabilize the acidity
What are the three features of the carbon dioxide - ventilation relationship?
1) partial pressure of CO2 level dramatically affects
ventilation rate
2) even with high O2 levels, CO2 is the
prime determinant
3) as partial pressure of O2 falls, the reaction to the partial pressure of CO2 is even greater
What are the peripheral chemoreceptors?
Aortic and carotid bodies
What are peripheral chemoreceptors most sensitive to?
O2 (much less to H+ and CO2 as seen in central chemoreceptors)
The peripheral chemoreceptors in the form of the aortic and carotid bodies (chemoreceptors) sample arterial blood and being firing when?
arterial partial pressure of O2 starts falling below 100 mmHg (and dramatically so below ~ 60 mmHg)
What do peripheral chemoreceptor in the form of the aortic and carotid bodies stimulate?
these sensors stimulate the dorsal respiratory group
Stimulation of the dorsal respiratory group by peripheral chemoreceptor in the form of the aortic and carotid
bodies will result in what?
Increased ventilation rate and depth
What limits the depth of breathing by inhibiting inspiratory neurons?
Pneumotaxic center
Increased pneumotaxic action results in
Short inspiration (rapid breathing)
Decreased pneumotaxic action (no inhibition) leads to
Lengthened inspiration (restful breathing)
Resting inspiratory neurons and increased ramp signal coincide with
Phrenic output and contraction of diaphragm and external intercostals
Expiratory neurons and DEcreased ramp signal coincide with
Contraction of internal intercostal
What neurons bypass respiratory control center?
Corticospinal and corticobulbar tracts
