PSL301: Respiratory 5 Flashcards
Neural regulation of breathing
Ondine’s curse is also known as…
congenital central hypoventilation syndrome
what is Ondine’s curse?
breathe normally during the day, but can’t breathe at night (attached to ventilator)
What controls respiratory muscles?
spinal motor neurons
What controls the diaphragm
Phrenic motoneurons / phrenic nerve
Where are phrenic motoneurons found?
cervical spinal cord segments C3, C4, C5
phrenic nerve is made up of…
phrenic motoneuron axons
What controls the intercostal muscles?
motoneurons for intercostal nerves
where are the motoneurons for intercostal nerves found?
Thoracic spinal cord segments T1 to T12
List the segments of the spinal cord from top to bottom
cervical
thoracic
lumber
sacral
the rhythmic activity of respiratory motor neurons are mainly controlled by…
premotor neurons in the medulla
What is the relationship between inspiration/expiration and phrenic nerve activity?
- rapid positive feedback loop for phrenic nerves (more and more active neurons)
- this increasing activity leads to inspiration
- activity suddenly stops = expiration
- no nerve activity during expiration
Why is there no phrenic nerve activity during expiration?
expiration is a passive process under normal conditions
DRG
dorsal respiratory group
VRG
ventral respiratory group
NTS
nucleus tractus solitarius
PRG
pontine respiratory group
Higher brain centers that control breathing connects to… (and where is it located?)
limbic system –> PRG in the pons
How does higher brain centers influence breathing?
sending axons to the different reasons in the medulla (which then sends motor neurons to the respiratory muscles)
Where is DRG located?
in the NTS
PRG sends info to the…
- NTS
- VRG
NTS sends info to the…
- inspiratory muscles
- PRG (feedback)
NTS is located in the…
medulla
What is located on the NTS?
medullary chmoreceptors
NTS houses…
DRG
VRG sends info to the…
expiratory, inspiratory, pharynx, larynx, tongue muscles
NTS receives input from…
sensory input from CN IX, X
- mechanical & chemosensory information about stretch of the lungs
What 2 things in the NTS and VRG sends info to each other?
DRG pre-Botzinger complex
respiratory neurons display
mutual inhibition (inspiratory inhibits expiratory and vice versa)
Which neurons are fired during inspiration?
- I INC
- I DEC
- I CON
Which neurons are fired during expiration?
- E INC
- E DEC
What does the I INC mean?
During inspiration, neuron firing rate increases
What does I CON mean?
During inspiration, neuron firing rate is constant
What does E DEC mean?
During expiration, neuron firing rate decreases
____ produces respiratory rhythm
rhythm generating neurons in the pre-Botzinger complex
where are the pattern generating neurons mainly located?
VRG
____ controls the pattern of activation in the pre-motor neurons
pattern generating neurons
What does rhythm generating neurons do?
produces respiratory rhythm (pacemaker activity)
Where are rhythm generating neurons located?
pre-Botzinger complex
What does pattern generating neurons do?
controls the pattern of activation in the pre-motor neurons
Function: afferent relay neurons
- integrate peripheral afferent inputs
- distribute info to rhythm and pattern generating neurons
Where are afferent relay neurons mostly located?
DRG
Function: cranial motoneruons
activate muscles of airway & bronchiolar smooth muscle
Location: cranial motoneurons
nucleus ambiguus (part of VRG)
muscles of the airway include…
- larynx
- pharynx
Function: pre-motor neurons
activate respiratory motoneurons in the spinal cord
What are the respiratory motoneurons?
- phrenic
- intercostal
Where are pre-motor neurons located?
VRG
DRG
respiratory neurons in the pons receive sensory info from…
DRG
What does respiratory neurons influence?
initiation & termination of inspiration
function: pontine respiratory group
provide tonic input to medulla –> coordinate smooth respiratory rhythm
What happens during forced breathing?
- some neurons in medulla becomes activated
- activation of accessory muscles for inspiration
- activation of internal intercostals & abs for expiration
example of accessory muscle activated during forced breathing
sternocleidomastoids
example of when forced breathing occurs
exercise
Respiratory generating neurons can…
1) function as network that oscillates: connected together synaptically
2) be pacemaker cells
3) both
What happens during initial phase of hypoxia?
- augmentation of breathing rate
- sigh
What happens during late phase of hypoxia?
- depression of breathing rate
- gasping
Difference of respiratory pattern in whole animal vs. medulla slice as observed from the pre-Botzinger complex
medulla slice is…
- fictive eupnea
- fictive sigh
- fictive gasping
rhythmic breathing is controlled by…
medulla & pons
rhythmic breathing can be affected by
- voluntary control from motor cortex
- chemoreceptors
- reflexes
- posture
- startling events
- emotions
- exercise
- pain
reflexes that affect breathing
sneezing, coughing
how does posture affect breathing?
affects intercostal & abdominal muscles
does pain increase or decrease breathing?
increase
Which 2 factors that affect rhythmic breathing goes through reticular formation?
- emotions –> limbic system
- sensory stimuli (pain, startling events)
3 efferent motor pathways of breathing. Which are the main pathways?
1) brainstem –> spinal phrenic motoneurons –> phrenic nerve –> diaphragm
2) primary motor cortex –> spinal phrenic motoneurons –> phrenic nerve –> diaphragm
3) premotor cortex –> spinal phrenic motoneurons –> phrenic nerve –> diaphragm
(1) and (2) are main
peripheral chemoreceptors are affected by…
pO2 and [H+]
- more sensitive when there is low O2
- respond to high H+
receptors in the respiratory system
- central chemoreceptors
- peripheral chemoreceptors
- airway & lung receptors
location: central chemoreceptors
medulla
location: peripheral chemoreceptors
carotid artery & aorta
central chemoreceptors are affected by…
[H+]
- respond to high H+
peripheral chemoreceptors send signals via the ___ nerve to ____
glossopharyngeal nerve
medullary respiratory neurons
airway & lung receptors send signals via the ___ nerve to ____
vagus
medullary respiratory neurons
central chemoreceptors send info to…
medullary respiratory neurons
medullary respiratory neurons sends signals to the upper airway muscles via the ___ nerve
vagus
medullary respiratory neurons send signals to…
- spinal respiratory motoneurons
- upper airway muscles
- airway smooth muscle
pathway from medullary respiratory neurons to pulmonary ventilation
- medullary respiratory neurons
- spinal respiratory motoneruons
- respiratory muscles
- pulmonary ventilation
feedback of respiratory muscles
- muscle receptors
2. spinal respiratory motoneurons
pO2 and [H+] levels are affected by…
pulmonary ventilation
airway & lung receptors receive signals from…
pulmonary ventilation
what are the types of airway & lung receptors?
- stretch receptors (mechanoreceptors)
- irritant receptors (C-fiber endings)
stretched out lungs signal…
the end of inspiration
stretch receptors are composed of…
- slow adapting receptors
- rapidly adapting receptors
irritant receptors responds to…
some irritant in the airway
location: stretch receptors
trachea to bronchioles
stretch receptors send signals via the …
vagus nerve
Hering–Breuer reflex
reflex triggered to prevent over-inflation of the lungs
stretch receptors activate the ____ reflex
Hering-Breuer
How does the stretch receptors activate the Hering-Breuer reflex?
stretch receptors present in the smooth muscle of the airways respond to excessive stretching of the lung during large inspirations –> send signal to medulla –> inhibits inspiration signals
the Hering-Breuer reflex is more common in…
animals
main function of stretch receptors in humans
1) control breathing pattern (TV & rate)
2) dyspnoea
define: dyspnoea
- breathing discomfort
- difference between what the control system wants and what is actually achieved
- chemoreceptor signals wanted
- stretch receptor signals achieved
location: irritant receptors
throughout the airway
irritant receptors trigger…
- breathing & bronchioconstriction
- several reflexes
what are the reflexes initiated by irritant receptors?
- sneeze
- aspiration
- cough
- sighs
which receptor causes the sneeze reflex?
nasal
which receptor causes the aspiration reflex?
epipharyngeal
which receptor causes the cough reflex?
- laryngeal
- tracheal
which receptor causes the sigh reflex?
- juxtapulmonary capillary (J-receptors)
which nerve sends the sneeze signal to the medulla?
trigeminal nerve
which nerve sends the aspiration signal to the medulla?
glossopharyngeal
which nerve sends the cough signal to the medulla?
vagus
which nerve sends the sigh signal to the medulla?
vagus
What causes congenital central hypoventilation syndrome?
PHOXb2 gene: codes for TF that doesn’t work as well as normal one
what is found in mutant genotype for congenital central hypoventilation syndrome
increased number of Ala
Function of Phoxb2
needed for development of autonomic neurons
people with congenital central hypoventilation syndrome have problems with…
- breathing when sleeping
- ANS
What happens in congenital central hypoventilation syndrome?
- alveolar hypoventilation during sleep & wake
- bad respiratory control
- less / no response to hypercabia & hypoxemia
- ANS dysregulation
Where is PHOX2B gene expressed?
- pFRG parafacial respiratory group (pFRG)
- retrotrapezoid nucleus (RTN)
In addition for the site of PHOX2B action, pFRG and RTN are the site of…
- have central chemoreceptors
- receives info from peripheral chemoreceptors
what is used as a treatment for congenital central hypoventilation syndrome?
Phrenic nerve pacemaker
what does the phrenic nerve pacemaker do?
stimulate phrenic nerve to bypass all the happenings in the brain
signal causes diaphragm to contract
