Respiratory System Flashcards
Why study neural respiratory control?
- respiratory neurons generate a most important rhythm pivotal for oxygen supply for energy utilization (apnea and fentanyl crisis)
- treatment of respiratory-related disease (sleep apnea. SIDS, AOP, CCHS)
- model for structure-function relation of neural networks (respiratory networks remain active in vitro –> easy to study)
What is an easy way to measure inspiratory rhythm?
EMG electrodes attached to genioglossus mm in TONGUE
Why do we record EMG activity from the genioglossus muscle to assess inspiratory rhythm?
- genioglossus mm CONTRACTS during inspiration to maintain/keep upper airways (pharynx) open
- genioglossus mm innervated by CN XII hypoglassal nerve
Which cranial nerve is associated with inspiratory rhythm?
CN XII hypoglossal nerve
What are the 3 major medullary respiratory groups?
- pontine (PRG)
- dorsal (DRG)
- ventral (VRG)
Which respiratory group contains inspiratory neurons?
PRG, DRG, VRG
Which respiratory group contains ONLY inspiratory neurons?
DRG
Which respiratory group contains expiratory neurons?
PRG, VRG
Which respiratory group contains both expiratory and inspiratory neurons?
PRG and VRG
Which respiratory group contains ONLY expiratory neurons?
none
In which brains structures of the PRG, DRG, and VRG found?
- PRG in DORSAL pons
- DRG in DORSOMEDIAL medulla
- VRG in VENTRAL medulla
What is the reference point for the location of respiratory neurons?
obex (opening of the 4th ventricle)
Which respiratory group’s neurons belong to the NTS?
DRG
Which respiratory group is important for sensory integration of respiratory activity?
PRG and DRG
Which respiratory group is important for generating the primary rhythm?
VRG
What is the most important respiratory muscle?
diaphragm
Contraction of the diaphragm causes a/an ______________ in the volume of the ribcage. (increase/decrease)
This induces the _____________ phase of breathing. (inhalation/exhalation)
increase; inhalation
TRUE or FALSE: during normal breathing, exhalation is caused by contraction of the diaphragm.
FALSE: exhalation occurs PASSIVELY
What is exhalation mediated by in normal breathing?
recoil force of the tendons attached to the respiratory muscles (PASSIVE)
Which muscles are activated during active expiration?
abdominal muscles: rectus abdominus, external oblique, internal oblique, transverse dominus
Which muscles are activated during normal expiration?
internal intercostals
Which muscles are activated during inspiration?
external intercostals
Which respiratory group drives the respiratory muscles?
VRG
Which nerve innervates the diaphragm?
phrenic nerve
What are the 3 phases of respiratory rhythm?
- inspiratory (I)
- pot-inspiratory (PI)
- active expiratory (E2)
Which nerve is active during inspiratory rhythm? expiratory rhythm?
- inspiratory = phrenic nerve
- expiratory = intercostal nerve
TRUE or FALSE: activation of the phrenic nerve stops abruptly after the inspiratory phase.
FALSE: activation increases during inspiratory phase and slowly declines during post-inspiratory phase
TRUE or FALSE: the phrenic nerve becomes silent during the E2 phase
TRUE
Which level of the spinal cord innervates the phrenic nerve? Which muscle does this nerve innervate?
- C3-C6
- diaphragm mm
Which level of the spinal cord innervates the thoracic to intercostal nerve? Which muscle does this nerve innervate?
- T1-T2
- intercostal mm ( internal for expiratory)
In a diagram, demonstrate the activity of the phrenic nerve vs the intercostal nerve during the 3 respiratory rhythm phases.
slide 4
Which substance blocks GABAa receptors? glycine receptors?
- bicuculline blocks GABAa
- strychnine blocks glycine receptors
Respiratory neurons in newborns already show IPSPs that cause hyperpolarization. What does this indicate?
respiratory network is ALREADY MATURE AT BIRTH, unlike hippocampal and cortical neural networks in which GABA and glycine evoke spontaneous rhythmic DEPOLARIZATIONS
Within the VRG, what area is critical for rhythm generation in respiration?
pre-Botzinger complex
TRUE or FALSE: the pre-botc is very thin
TRUE
what kind of respiratory rhythm does the pre-BotC generate?
inspiratory
TRUE or FALSE: preBotC neurons excite expiratory neurons and inhibit inspiratory neurons during the expiratory phase.
FALSE: excite inspiratory neurons, inhibit expiratory neurons during inspiratory phase
TRUE or FALSE: mainly inspiratory neurons are found in the pre BotC
TRUE
Which cranial nerve is related to inspiratory activity?
CN XII (hypoglossal)
(hint: record activity of genioglossus muscle shows)
Inspiratory active pre-BotC neurons show rhythmic cytosolic Ca2+ ____________ (rises/falls) due to their rhythmic rhythmic ____________ (depolarizations/hyperpolarizations).
rises; depolarizations
How does the addition of TRH affect Ca2+ enhanced inspiration in sighing?
Ca2+ rises are very regular and uniform, showing only eupnea-like inspiratory events
What does a eupnea-like vs inspiratory sigh look like in terms of Ca2+ rises?
- eupnia: small amplitude
- sigh: large amplitude
What is eupnea?
normal inspiration
TRUE or FALSE: rhythm generation depends on mutual inhibition
FALSE: rhythm generation does NOT depend on mutual inhibition
How are we able to determine that the inspiratory rhythm does not depend on GABAa and glycine receptors?
when strychnine and bicuculline are administered in VRG neurons, inspiratory bursting is not inhibited
Describe the emerging network model of pre-botC rhythm generation.
- post-burst hyperpolarization: synapses silent (end of PI)
- recovery: endogenous activity resumes (some rhythmogenic neurons activate)
- recurrent excitation: positive feedback (rhythmogenic neurons stimulate their neighbours)
- burst: synaptic excitation evokes intrinsic currents
(cycle back to 1)
TRUE or FALSE: inspiratory neurons are dependent on GABAergic neurons
FALSE: dependent on glutamatergic neurons
What are the 2 respiratory centers that make up the dual respiratory center in mammals? Which one is inspiratory/excitatory?
- preBotC = inspiratory
- RTN (retroptrapezoid nucleus)/pFRG (parafacial respiratory group) = expiratory
Why is the expiratory center often named RTN/pFRG?
pFRG area fully overlaps with RTN area which contains chemosensitive respiratory and non-respiratory neurons
during which phase is pFRG active?
post-inspiratory phase
TRUE or FALSE: opioids block inspiratory but not expiratory rhythm.
TRUE
How does fentanyl affect abdominal muscle activity vs inspiratory-related airflow?
- abdominals: regular pre-inspiratory bursting
- airflow: slowed down
which substance kills pre-BotC neurons that express NK1 subtype of substance P receptors? How does it affect breathing? When does it affect breathing?
- saponin (SAP)
- depresses inspiration during REM sleep
TRUE or FALSE: NK1 receptor-expressing pre-BotC neurons are important for rhythm generation.
TRUE
