Control of Breathing Flashcards
Spontaneous respiration is produced by what?
Rhythmic discharge or motor neurons that innervate the respiratory muscles
How are the pons regulated (through what changes)?
Alterations in PO2, PCO2, and H+ [c]
nonchemical influences
Where are the autonomic breathing centers of the brain? Where do these places send impulses to?
Pons and medulla, send impulses to respiratory motor neurons
Where are the voluntary breathing centers of the brain? Where do these send signals to?
Cerebral cortex sends signals to the respiratory motor neurons in the spinal cords
How are the motor neurons to the expiratory muscles and inspiratory muscle regulated?
The motor neurons to the expiratory muscles are inhibited when those supplying the inspiratory muscles are active, and v.v.
Changes in PCO2, PO2, and pH directly stimulate what area?
The peripheral chemoreceptors
What is the most important chemoreceptors for respiration?
arterial PCO2 receptors
How does arterial PCO2 receptor firing change relative to ventilation?
Inversely
Which has a stronger effect on respiration: pH changes or pCO2 changes?
PCO2 changes
Can peripheral receptors for PO2 act indepently of PCO2 receptors?
Yes
What is the most sensitive range of PO2 in mmHg (the steepest pat of the graph)?
60-30 mmHg
How does H+ exert its effects on the stimulatory center?
Increased PCO2
Why doesn’t H+ directly affect the chemoreceptors in the brain?
Cannot pass the BBB very well
Where are the peripheral chemoreceptors located? What are they mainly stimulated by?
Aortic arch
Carotid bodies
Mainly PO2 changes
The sensory bodies in the aortic arch and the carotid bodies respond mainly to what chemical change?
PO2
The chemosensitive areas of the CNS are sensitive to what?
PCO2 and [H+]
What are the three areas of the CNS that sense PCO2 and H+?
Rostral area
Intermediate area
Caudal area
What are the two nerves that transmit the signals from the peripheral chemoreceptors to the CNS?
CN X and IX
Where do the vagus and CN IX send their signals to in the CNS (i.e what is the integration center in the brain for chemoreceptors)?
NTS
What are the pre-Botzinger complexes responsible for? Where are these located?
The rhythmic respiration
On either side of the medulla
After the peripheral chemoreceptors sense changes in PCO2, PO2, or pH, what happens? Where/through what nerves are signals sent?
Signals sent to the NTS via CN X and IX
What is the integrating center of the brain for chemoreceptor signals? What happens after signals are sent to this?
NTS
Relays signal to the central pattern generator
What are the central chemoreceptors stimulated by? What effect does this cause?
PCO2, sends signals to the central pattern generator
Where do signals that are sent to the pattern generator go?
Spinal cord, to the muscles of respiration
Where does the higher CNS system overtake the autonomic respiratory center?
At the spinal cord
What part of the breathing innervation pathway do the central and peripheral respiratory receptors have in common?
Central pattern generator
Which nerves in the spinal cord are utilized to send respiratory signals?
CN VII, IX, X, XI, XII
Through what chemoreceptors do PO2 and pH exert their effects?
Peripheral only
How do the rates of stimulation compare between the central and peripheral chemoreceptors?
The stimulation by way of the peripheral chemoreceptors occurs as much as five times as rapidly as central stimulation
True or false: changes in arterial H+ directly act on
central chemoreceptors
False-
Rather, in the chemosensitive
area, CO2 diffuse in through the blood brain barrier and is
converted locally to H+ via formation and dissociation of
carbonic acid
True or false: O2 does not have a direct effect on the respiratory center
True
True or false: the carotid bodies measure the arterial blood directly in the carotid artery
False - Each of the chemoreceptor bodies receives its own special blood supply through a minute artery
directly from the adjacent arterial trunk
How do the carotid bodies only receive arterial/oxygenated blood?
blood flow through these bodies is extreme, 20
times the weight of the bodies themselves each minute. Therefore, the percentage of O2 removed
from the flowing blood is virtually zero.
The respiratory center is located bilaterally in the medulla oblongata and pons of the
brain stem. It is divided into four major collections of neurons. What are their names?
- The pre-Bötzinger complex
- The dorsal
respiratory group - The ventral respiratory group
- The pneumotaxic respiratory group.
What is the function of the NTS?
Relay and integrate signals from the peripheral chemoreceptors to the respiratory centers of the brain
What is the function of the Pre-Bötzinger Complex?
produce rhythmic discharges
What is the function of the dorsal respiratory group?
sends out repetitive bursts of inspiratory
neuronal action potentials (inspiratory ramp
signals
- main role in controlling inspiration
What is the function of the pneumotaxic center/
controls the “switch-off” point of the
inspiratory ramp thereby controlling rate & depth of breathing
What is the function of the ventral respiratory group?
Contributes to both inspiration and expiration – especially important in providing the powerful expiratory signals to the abdominal muscles during very heavy expiration.
totally inactive during normal quiet respiration
Normally, the ventral respiratory group is totally inactive. What activates it?
When the respiratory drive for increased pulmonary ventilation becomes greater than normal,
respiratory signals spill over into the VRG (DRG VRG)
What is the “pacemaker” of respiration?
The Pre-Bötzinger Complex
Which part of the brain controls that inspiratory ramp signal?
The DRG (dorsal respiratory group)
Which part of the brain sends signals to the DRG to “switch off” the ramp signal produced by the DRG?
the pneumotaxic center
Which part of the brain is usually inactive, but becomes activated when signals spill over from the DRG, and acts to provide additional signals to the abdominal muscles?
VRG (ventral respiratory group)
What is the relationship between ventilation and oxygen consumption during exercise?
Both increase in a linear fashion
What causes the increase in breathing during exercise?
The brain, not the autonomic breathing centers
Where are irritant receptors located in the body?
Epithelium of the trachea, bronchi, and bronchioles
What are the “J receptors”? What area do they face? Activation of these produces what?
Sensory nerve endings in the alveolar walls that face the interstitium, and are sensitive to edema.
These gives the SOB sensation
What is the effect on brain edema on the respiratory center? What is the treatment for this?
Depressed or inactivated
Hypertonic solutions can relieve this effect quickly
What reflex are the stretch receptors in the bronchi and bronchioles responsible for? What is this reflex?
The Hering-Breuer inflation reflex
Activation of receptors leads to “switch off” of the DRG to stop further inspiration
When is the Hering-Breuer inflation reflex activated?
When Vt >3x normal
What is Kussmaul’s breathing? When is it seen?
Rapid, deep and labored breathing, seen in acidosis
What is Cheyne-Stokes breathing? When is it seen?
Intermittent periods of apnea, followed by slowly increased Vt, then decreased Vt until back to apnea
This is seen in stroke, encephalopathies, heart failure
What is Biot’s breathing? When is it seen?
Groups of quick, shallow inspirations, followed by regular or irregular period of apnea
Seen in medullary trauma, stroke
