Respiratory control Flashcards
what two variables of breathing does the brain (thru phrenic nerve and medullary center) control?
frequency and tidal volume
(Vt) VE= f*Vt
determines timing (f)—> determines depth (VT)—-> to motorneurons
is phrenic firing during inspiration or expiration?
inspiration
what is the site in the medulla that tell lungs when to breath? (generating first part of timing/frequency of respiratory rhythm)?
pre-botzinger complex
*fires more at beginning of respiration
what is the bart of medulla that controls length of inspiration (second part of timing/frequency of respiratory rhytm)?
PRG
what happens when there is a lesion in the PRG?
lose ability to turn off inspiration without help from vagus nerve—> apneusis (stuck in inspration)
what part of medulla sends sensory info to lungs to generate its breathing pattern (how fast/deep/etc)?
DRG (responsible for 95% of phrenic motor input)
what part of medulla gives a smaller motor input to phrenic nerve and inspiratory muscles to control breathing pattern?
what part sends input to the upper airway and muscles of expiration?
rostral VRG
caudal VRG
what is the appearance of inspiration in:
apenuesis?
of apnea?
apneuisis: maintained inspiration
apnea: no inspiration (absence of effort)
what are the results of:
apneusis?
apnea?
apneusis: pontine damage
apnea: medulla or spinal cord damage
what are the effects of:
apeursis?
apnea?
apneusis: slight delay, but then increase in CO2, decrease O2, death if not treated
apnea: increase in CO2, decrease O2, death if not supported
what are chemoreceptors in respiratory system?
what do they respond to?
why are they so important?
neurons that increase firing rate in response to
- increse CO2
- increase O2
- increase H
these condtions normally decrease activity in respiratory neurons (decrease during hypoxia or hypercapnia)–> decrease ventilation and gas exchange–> exacerbates problem–>
chemoreceptors stop this from happening by activating respiratory centers and increasing respiration–> keeping us alive!!
what is chemosensitvity?
ability of certain chemicals to change discharge rate of sensitive neurons
what are the two set of respiratory chemoreceptors, where are they located, and what are they sensitve to?
- central
- ventral surface of medulla
- directly to pH of CSF and indirectly to CO2 in blood/plasma
- peripheral
- aortic arch and (more importantly) carotid body
- decrease in O2, increase in CO2, increase in H+
*carotid body also sensitive to dopamine
how do the central chemoreceptors respond indirectly to CO2 in the blood?
CO2 crosses BBB–>
mixes with H2O—>
forms H2CO3 via carbonic anhydrase—>
rapidly breaks down to form H and CO3—>
H then stimulates chemoreceptors
**must happen this way because H+ cannot cross BBB
what drives us to breathe?
stimulation of central chemoreceptors by H+
how do peripheral chemoreceptors differ from central chemoreceptors?
- more sensitive to O2
- increased frequency of afferents from carotid body/aortic arch
- increased Vt
- quicker than central
- stimulated also by O2, CO2, pH BUT it is directly for both (plus it responds more to O2)
what influence does peripheral chemoreceptors have?
acute changes in blood gases
what conditions do central chemoreceptors respond to?
what are the effects of?
hypercapnia (slower than peripheral)
increase in respiratory rate, depth of breath
what do peripheral chemoreceptors respond to?
what is there effect?
hypercapnia, hypoxia, acidosis
increase in respiratory rate and depth in breath
where are slow-adapting pulmonary stretch receptors located?
sensitive to?
where do fibers travel?
what is their effect?
airways
stretch of airways (directly proportional to lung volume)
travel to brain in Vagus nerve
inhibit inspiration and prolong expiration
what can bypass medullary centers and send input directly to muscels of respiration?
cortex!
help control breathing when holding your breath and talking
who are the slow-adapting pulmonary stretch receptors important for controlling respiration in?
infants- because babies dont use lungs in utero (every breath)
adults who are exercising (so not every breath)
**not crucial in controlling Vt in adults at rest
where are rapidly-adapting pulmonary stretch receptors located?
sensitive to?
fibers travel where?
their effect?
airways
irritation, foreign bodies in airways, stretch
to brain in vagus
cough
where are the J (juxtacapillary) receptors located?
sensitive to?
fibers travel where?
effects?
near blood vessels of alveoli
pulmonary edema
to brain in vagus
cough, tachypnea
what are the J receptors and the rapidly adapting pulmonary stretch receptors main roles?
protecting the gas exchange surfaces by overriding the normal respiratory control systems (obviously not with every breath)
very important for survival!
