Respiration III Flashcards
“BODY” implies ________.
chemoreceptor.
The carotid body is composed of both type I cells (______ cells) and type II cells (_____-_____ ________ _____).
type I - glomus cells
type II - glial-like ensheathing cells
Type I and type II cells are derived from the same origin as neurons. Note, however, that type I cells have no ______ or ______.
dendrites or axons.
Which nerve carries afferent information away from the carotid body and baroreceptors at the carotid sinus? This nerve is a branch of the _______________ nerve.
Carotid sinus nerve. It is a branch of the glossopharyngeal nerve.
The afferents of both carotid bodies and aortic bodies terminate at the ____. This is where integration of the afferent information occurs.
NTS.
In response to hypoxia, type I cells cause an increase in afferent activity leaving the glossopharyngeal nerve (cranial nerve ____). Outline the process by which this occurs.
CN IX.
- low PaO2 “somehow” results in an increased membrane potential of the type I cell
- This causes voltage gated Ca2+ channels to open, allowing Ca2+ into the type I cell
- This stimulates the release of ATP from the cell via exocytosis of vesicles containing it.
- ATP binds to P2X (purinergic) receptors on CN IX.
- Na+ and Ca2+ enter CNIX (P2X receptors are non-selective cation channels)
- Nerve membrane potential is increased and more likely to fire AP.
In response to hypercapnia, type I cells cause an increase in afferent activity leaving the glossopharyngeal nerve (cranial nerve __). Outline the process by which this occurs.
- Intracellular Ca2+ increases
- ATP release from type I cells
- glossopharyngeal nerve activity increases
What functional changes occur to respiration when peripheral chemoreceptors are activated during hypoxia?
- increase in tidal volume
- increase in respiratory frequency
- increase in sympathetic activity (increase in heart rate, slight increase in blood pressure).
Outline the projections from peripheral chemoreceptors that ultimately lead to an increase in respiration during HYPOXIA.
Peripheral chemoreceptors —> NTS —> VRG —> phrenic motor neurons —> respiration increases.
Outline the projections from peripheral chemoreceptors that ultimately lead to an increase in sympathetic activity during HYPOXIA.
Peripheral chemoreceptors —> NTS —> RVLM (rostral ventral lateral medulla) —> IML (intermediate lateral cell column in spinal cord - sympathetic neurons) —> sympathetic activity increases.
P2X receptors are _______.
P2Y receptors are _______.
P2X - ionotropic
P2Y - gpcrs
What area do the central chemoreceptors we looked at in the lecture affect?
The RTN (retrotrapezoid nucleus).
Where, more precisely, is the RTN?
On the very ventral surface of the medulla (right at the base of the brainstem).
Where does the RTN project to in order to increase 1) respiration and 2) sympathetic activity.
1) NTS, VRG
2) RVLM
Outline the process by which central chemoreceptors (VMS astrocytes) increase the activity of RTN neurons during HYPERCAPNIA.
- CO2 is a small, lipid-soluble molecule so it passes readily into the CSF
- CO2 + H20 = HCO3- + H+ This means that H+ concentration in CSF increases (pH is lowered)
- increase in H+ conc. in CSF results in closure of inward rectifying K+ channels
- this causes an increase of K+ within the astrocyte and therefore an increase in membrane potential
- this causes Ca2+ channels to open
- Ca2+ rushes into astrocyte
- ATP is released into the CSF
- ATP binds to P2Y receptors on RTN neurons
- activity of RTN neurons increases
Outline the 2 processes by which H+ ions can directly increase the activity of RTN neurons.
1)
- increase of H+ in CSF activates gpcr on RTN neuron
- this causes closure of K+ leak channel (and thus an increase in membrane potential)
- RTN neuron more excitable
2)
- increase of H+ in CSF causes closure of TASK-2 K+ channel on RTN neuron
- therefore more K+ inside cell and increase in membrane potential
- RTN neuron more excitable
What functional changes occur as a result of central chemoreceptor activation during HYPERCAPNIA?
- increase in tidal volume
- recruition of abdominal muscle activity during late expiration (evokes ACTIVE expiration).
Peripheral chemoreceptors cause an _______ in respiration and an ________ in sympathetic activity during hypoxia.
increase in respiration, increase in sympathetic activity.
Stimulation of the RTN causes an _______ in respiration and an _________ in sympathetic activity during hypercapnia.
increase in respiration, increase in sympathetic activity.
What happens to respiration during exercise?
1:1 coupling (also called locomotor-respiratory coupling). System tightly couples breathing to exercise being performed.
Which of the 3 phases of breathing is modulated in order for 1:1 coupling to occur? How is it modulated?
Post-inspiratory phase is shortened.
What stimulus causes a reset in respiratory rhythm?
Afferent feedback from contracting muscles.
Somatosensory afferents from muscles project to which two areas?
- NTS (important for baroreceptor resetting during exercise)
- Pons
Blocking the Pons during exercise causes a return to regular respiratory rhythm (no longer coupled with somatic stimulation). What does this mean?
Respiratory resetting is mediated by the Pontine respiratory group.
