Respiration III Flashcards

1
Q

“BODY” implies ________.

A

chemoreceptor.

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2
Q

The carotid body is composed of both type I cells (______ cells) and type II cells (_____-_____ ________ _____).

A

type I - glomus cells

type II - glial-like ensheathing cells

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3
Q

Type I and type II cells are derived from the same origin as neurons. Note, however, that type I cells have no ______ or ______.

A

dendrites or axons.

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4
Q

Which nerve carries afferent information away from the carotid body and baroreceptors at the carotid sinus? This nerve is a branch of the _______________ nerve.

A

Carotid sinus nerve. It is a branch of the glossopharyngeal nerve.

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5
Q

The afferents of both carotid bodies and aortic bodies terminate at the ____. This is where integration of the afferent information occurs.

A

NTS.

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6
Q

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.

A

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.
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7
Q

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.

A
  • Intracellular Ca2+ increases
  • ATP release from type I cells
  • glossopharyngeal nerve activity increases
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8
Q

What functional changes occur to respiration when peripheral chemoreceptors are activated during hypoxia?

A
  • increase in tidal volume
  • increase in respiratory frequency
  • increase in sympathetic activity (increase in heart rate, slight increase in blood pressure).
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9
Q

Outline the projections from peripheral chemoreceptors that ultimately lead to an increase in respiration during HYPOXIA.

A

Peripheral chemoreceptors —> NTS —> VRG —> phrenic motor neurons —> respiration increases.

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10
Q

Outline the projections from peripheral chemoreceptors that ultimately lead to an increase in sympathetic activity during HYPOXIA.

A

Peripheral chemoreceptors —> NTS —> RVLM (rostral ventral lateral medulla) —> IML (intermediate lateral cell column in spinal cord - sympathetic neurons) —> sympathetic activity increases.

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11
Q

P2X receptors are _______.

P2Y receptors are _______.

A

P2X - ionotropic

P2Y - gpcrs

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12
Q

What area do the central chemoreceptors we looked at in the lecture affect?

A

The RTN (retrotrapezoid nucleus).

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13
Q

Where, more precisely, is the RTN?

A

On the very ventral surface of the medulla (right at the base of the brainstem).

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14
Q

Where does the RTN project to in order to increase 1) respiration and 2) sympathetic activity.

A

1) NTS, VRG

2) RVLM

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15
Q

Outline the process by which central chemoreceptors (VMS astrocytes) increase the activity of RTN neurons during HYPERCAPNIA.

A
  • 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
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16
Q

Outline the 2 processes by which H+ ions can directly increase the activity of RTN neurons.

A

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

17
Q

What functional changes occur as a result of central chemoreceptor activation during HYPERCAPNIA?

A
  • increase in tidal volume

- recruition of abdominal muscle activity during late expiration (evokes ACTIVE expiration).

18
Q

Peripheral chemoreceptors cause an _______ in respiration and an ________ in sympathetic activity during hypoxia.

A

increase in respiration, increase in sympathetic activity.

19
Q

Stimulation of the RTN causes an _______ in respiration and an _________ in sympathetic activity during hypercapnia.

A

increase in respiration, increase in sympathetic activity.

20
Q

What happens to respiration during exercise?

A

1:1 coupling (also called locomotor-respiratory coupling). System tightly couples breathing to exercise being performed.

21
Q

Which of the 3 phases of breathing is modulated in order for 1:1 coupling to occur? How is it modulated?

A

Post-inspiratory phase is shortened.

22
Q

What stimulus causes a reset in respiratory rhythm?

A

Afferent feedback from contracting muscles.

23
Q

Somatosensory afferents from muscles project to which two areas?

A
  • NTS (important for baroreceptor resetting during exercise)

- Pons

24
Q

Blocking the Pons during exercise causes a return to regular respiratory rhythm (no longer coupled with somatic stimulation). What does this mean?

A

Respiratory resetting is mediated by the Pontine respiratory group.

25
Q

The Pons influences which neurons specifically?

A

Post-inspiratory neurons.