10- Ventilatory Control and the Chemoreflexes Flashcards

1
Q

What are the 3 components of the respiratory control system?

A

controller: neurons in the brainstem that send signals to the respiratory muscles

effector: components of the system that carry out gas exchange processes

sensor elements: provide feedback and excitatory input

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2
Q

What is the purpose of the rhythm generator?

A
  • rhythm generating neurons (intrinsic oscillator) provide the “trigger” or signal that initiates the respiratory cycle
  • then rhyhtm generator is thought to tactivate pattern generating neurons whih provide for the proper sequential activation of respiratory pump and airway motorneurons
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3
Q

What happens when you injure the rhythm generator?

A

abrupt injury leads to destruction. but there is a lot of plasticity so gradual injury is ok!

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4
Q

WHat is the sequence of influences that lead to breathing?

A

Rhythm generator (timing)

pattern formation ( shaping)

pre-motor neurons (integration)

Motor neurons (motor output)

sequence of rhythm generation, to pattern formation (or shaping), to an integrating mechanism, and finally to motorneurons that acitvate the respiratory muscles

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5
Q

What are the sensors?

A

carotid body (made up of gloma cells)

aortic body

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6
Q

What is the hypoxic ventilatory chemo reflex? Start with decreased inspired PO2…..

A

decreased inspired Po2

decreased alveolar Po2

decreased arterial Po2

Peripheral chemoreceptors (inrease firing)

Respiratory muscles (increase contractions)

Ventilation increases

Return of alveolar and rterial PO2 toward normal

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7
Q

Ventilation changes in parallel with _________________

A

changes in carotid chemoreceptor activity

increased carotid chemoreceptor activity leads to increased ventilation›

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8
Q

WHere are the CO2/H chemoreceptors located?

A
  • identified at multiple sites in the brainstem
  • hypothesized to determine physiologic functions in addition to breathing
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9
Q

What are the 4 sites of respiratory chemoreceptors? Which is likely the most important?

A

Pre-Botzner complex

Retrotrapezoidal nucleus (most important)

lateral parapyramidal area

nucelus tractus solitarius

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10
Q

What is the hypercapnic ventilatory chemoreflex?

A

increased arterial CO2 leads to increased H centrally and peripherally

this leads to increased peripheral and central chemoreceptor firing

increased firing of medullary neurons

increased firing of neurons to diaphragm and inspiratory intercostals

DIaphragm and inspiratory intercostals increase contraactions

increased ventilation

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11
Q

What happens when you cooling (inhibit) the RTN chemoreceptors in an awake animal vs asleep animal? What is the significance of this?

A

Anesthetized: stop breathing

Awake: decrease breathing

the significance is that this implies that the RTN has a significant influence on breathign regulation. Howver it also proves it is not the only influence and that arousal is very important!

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12
Q

What are 4 neuromodulators that are active when your awake and what happens to their elvels when you are in non-REM sleep? What about REM sleep?

A

Raphe Nucleus

Locus coerulus

LDT. PPT nuclei

FTG

When you sleep the levels go down and you hypoventilate

When you are in REM FTG and LDT/PPT nuclei increase

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13
Q

What are the 3 excitatory stimuli that sustain activity and rhtyhm and pattern generating neurons?

A

Carotid chemoreceptor

state dependent neuromodulation

retrotrapezoid nucelus

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14
Q

The control system consist of what 3 parts?

A

controller (within brainstem)

effectors (lungs and respiratory muscles)

feedback (chemo and mechanoreceptors)

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15
Q

Basic components of the controller are the ____ and _________ generators which determine _____ and ___________-

A

basic components of the controller are the rhythm and pattern generators which determine breathing frequency and coordinated activity of respiratory muscle respectively

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16
Q

carotid chemoreceptors are activated by _______ and _____ while brainstem receptors are activated by _____

A

Carotid chemoreceptors are activated by low PaO2 and elevated PaCO2

brainstem receptors are activated by high PCO2

17
Q

What are the 2 primary roles of chemoreceptors?

A
  • inform the brainstem controllers of whether the control system is meeting the needs of gas exchange
  • to provide tonic input that maintains optimal levels of excitability of the respiratory rhythm and pattern generators
18
Q

What is critical to maintaining the excitability of the respiratory rhtyhm and pattern generators?

A

the balance of excitatory and inhibitory neuromodulators are critical to maintaining the excitability of the respiratory rhythm and pattern generators