Respiratory V Control of Respiration Flashcards
what is the ultimate goal of respiration
to maintain proper concentrations of O2, CO2 and H+ in the tissues
what brain tracts act in respiratory system
corticospinal tract act on muscles of breathing and ventrolateral tract
what do chemoreceptors respond to
only H+
what do peripheral chemoreceptors respond to
H+ , O2 and CO2
what are the only receptors that sense O2
peripheral receptors
what do excess CO2 and H+ do to respiratory centers
activates them to increase alveolar ventilation
what does decreased O2 do to alveolar ventilation
increases it
how does decreased O2 impact central respiratory centers
indirectly by acting on peripheral chemoreceptors that relay the signal to the central respiratory center
what are the 2 basic controls of breathing
-voluntary: corticospinal tract
- automatic: ventrolateral tract
describe the corticospinal tract
involves descending input form the thalamus and cerebral cortex, can bypass the respiratory control centers in pons and medulla
when is the corticospinal tract activated
during talking, sneezing, singing, swallowing, coughing, defecation, anxiety, fear
what is the ventrolateral tract sensitive to
-primarily controlled by changes in PCO2
- less sensitive to PO2 and H+
where are the receptors for the ventrolateral tract control located
pulmonary mechanical receptors
where is the ventrolateral tract located
activated by respiratory centers in the pons and medulla such as DRG and VRG
what two areas in the brainstem control respiration
-medullary respiratory centers
-pontine respiratory group
what makes up the medullary respiratory centers
-dorsal respiratory group (DRG)
- ventral respiratory group (VRG)
what make sup the pontine respiratory group
-pneumotaxic center
-apneustic center
where is the DRG located
in the nucleus of the tractus solitarius (NLS)
is the DRG involved in inspiration or expiration
inspiration
what neurons does the DRG receive afferent input from and what specific types of neurons are they
CN 9 (a peripheral chemoreceptor) and 10 (peripheral chemoreceptor and mechanoreceptor)
what type of stimulus does the DRG supply to what?
excitatory inspiratory stimuli to phrenic motor neurons
what does the DRG mainly do
set the basic rhythm for breathing by setting the frequency of inspiration - central pattern generator
describe the signal pattern sent by the DRG
signal begins weakly, increases steadily for 2 seconds, then will abruptly cease for ~3 seconds before resuming the cycle of 12-20 breaths for minute
what types of receptors does the DRG contain and what do they do when activated
-opiate receptors
- when activated inhibit respiration and decrease sensitivity to changes in PCO2
where is the VRG located
nucleus ambiguus and nuclues retroambiguus
is the VRG involved in inspiration or expiration
mostly expiration
are the neurons in the VRG active during normal breathing
no
when are neurons in the VRG activated
when forceful expiration is required
what does the VRG control motor neurons for
- expiratory muscles such as abdominals and internal intercostals
- accessory inspiratory muscles
- group of neurons in the pre-botzinger complex that have respiratory pacemaker control
what are the pontine respiratory centers
-pneumotaxic center
- apneustic center
what does the pneumotaxic center do when activated
shortens the time of inspiration
what is the relationship between the pneumotaxic center and the apneustic center
they are antagonists of each other
what does the apneustic center do when activated
causes excitation of the DRG which results in prolonged inspiration with brief periods of expiration
what is the summary of brainstem control of breathing
-afferent information regulates the activity of the medullary inspiratory center (DRG) via central and peripheral chemoreceptors and mechanoreceptors (lung stretch and muscle/joint receptors)
what are the respiratory reflexes that are sensitive to mechanical stimuli and what are the functions of each
- hering-breuer reflex (achieve optimal rate and depth)
- irritant receptors (protective)
- J receptors (Function unclear)
- joint and muscle proprioceptors
describe how the herin-breuer reflex works, what causes it, and the result
- stretch receptors in bronchi and bronchioles are activated when the lungs over stretch.
- to activate this reflex tidal volume must increase more than 3 times
- result: stops further inspiration and decreases rate
where are irritant receptors located, what are they stimulated by and what is the result
- located between epithelial cells in conducting zone
- stimulated by noxious exogenous substances, endogenous agents, and mechanical stimulation
-result: rapid, shallow breathing, coughing, sneezing
where are J receptors located, what are they stimulated by and what is the result
- located in alveolar walls next to capillaries
- stimulated by alveolar inflammatory processes (pneumonia), pulmonary vascular congestion (CHF) and edema
- result: rapid, shallow breathing and a sensation of dyspnea
what are joint and muscle proprioceptors sensitive to and what is the result
- sensitive to change in position and muscle movements not metabolism
- result: increase activity of DRG to increase rate of breathing
what is the purpose of joint and muscle proprioceptors
-automatically adjusts to load imposed by decreased lung compliance or increased airway resistance (weighted blanket)
- stimulate ventilation by slapping skin, cold water etc
what receptors are most important for minute to minute breathing
central chemoreceptors
where are central chemoreceptors located and what do they do when activated
-located on ventral surface of medulla
- activation of these stimulate the DRG
what are central chemoreceptors sensitive to
pH of CSF or in other words H+
what is a drop in CSF pH is reflective of
a higher than normal amount of PCO2
what happens when CSF [H+] increases
increase in respiratory volume and rate
does arterial [H+] activate central chemoreceptors
no
what is the mechanism of central chemoreceptors
-CO2 is permeable to the blood brain barrier
- in the CSF, CO2 is converted to H+ and HCO3- via carbonic anhydrase
- the H+ produced in the CSF activates the central chemoreceptors which stimulates the DRG
is the effect of a change in CO2 potent acutely or chronically
acutely
when are central chemoreceptors most effective and why
within 1-2 days because during and after that time period the kidneys will have begun to compensate and reabsorb HCO3- and HCO3- has slowly diffused through the blood brain barrier and CSF barriers will buffer H+
what is a danger for patients with chronic respiratory problems
the kidney and buffer mechanisms compensate for the elevated PaCO2 and H+ so that they no longer stimulate the medullary respiratory centers
- then the peripheral chemoreceptors become critical for respiratory control
where are peripheral chemoreceptors located
in the aortic bodies and carotid bodies
what nerves are located in each body where the peripheral chemoreceptors are located
- glossopharyngeal from the carotid bodies
- vagus from the aortic bodies
what are peripheral chemoreceptors sensitive to in arterial blood
- low PaO2, high PaCO2 and low pH
what happens to alveolar ventilation at PaO2 less than 60 mmHG
LARGE increase in alveolar ventilation
wwhy do PaO2 levels have to fall below 60 mmHg to have an effect on respiratory function
very sharp drop in Hb saturation so decreased ability to transport O2 to the tissues
what do increases in PaCO2 do to aortic and carotid bodies
increase the rateof firing of both of them
which response is more powerful to changes in PaCO2: peripheral chemoreceptor or central
central
which response is faster to changes in PaCO2 and by how much: peripheral chemoreceptor or central
-peripheral chemoreceptor by 5 times
what does decreased arterial pH affect the rate of
increase the rate of carotid bodies
how does hypoxia affect the response to PaCO2
it enhances it
after what pressure does PaCO2 stimulate an increase in alveolar respiration
after 35mmHg
which affects alveolar ventilation more easily: pH or CO2
CO2
what does metabolic acidosis do to PaCO2 response
enhance it
what decreases response to PaCO2
sleep, opiods, narcotics, chronic obstruction, and deep anesthesia
what do most inhaled anesthetics cause and how
respiratory depression by inhibiting the DRG and abolish the response to hypoxemia and hypercarbia (increased CO2)
what is the effect of NO on respiratory rate
increases respiratory rate and decreases tidal volume so there is minimal change in minute ventilation and PaCO2 levels
what does NO do to hypoxic drive
decreases it
what does NO do to PVR
increases it and decreases perfusion
what does NO do to the NS
mild activator of SNS
breathing is _____ controlled during sleep
less rigorously
what percentage of men and women have obstructive sleep apnea
4% and 2% women
what percentage of people with obstructive sleep apnea are undiagnosed
85%
what happens during obstructive sleep apnea
-when asleep the tone of the throat and tonuge muscles that maintain the opening of the ororpharynx decreases
