10 - Ventilatory Control and the Chemoreflexes

Question 1

What are the 3 components of the respiratory control system?

Answer 1

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

Question 2

What is the purpose of the rhythm generator?

Answer 2

• 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

Question 3

What happens when you injure the rhythm generator?

Answer 3

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

Question 4

WHat is the sequence of influences that lead to breathing?

Answer 4

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

Question 5

What are the sensors?

Answer 5

carotid body (made up of gloma cells)

aortic body

Question 6

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

Answer 6

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

Question 7

Ventilation changes in parallel with _________________

Answer 7

changes in carotid chemoreceptor activity

increased carotid chemoreceptor activity leads to increased ventilation›

Question 8

WHere are the CO2/H chemoreceptors located?

Answer 8

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

Question 9

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

Answer 9

Pre-Botzner complex

Retrotrapezoidal nucleus (most important)

lateral parapyramidal area

nucelus tractus solitarius

Question 10

What is the hypercapnic ventilatory chemoreflex?

Answer 10

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

Question 11

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

Answer 11

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!

Question 12

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?

Answer 12

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

Question 13

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

Answer 13

Carotid chemoreceptor

state dependent neuromodulation

retrotrapezoid nucelus

Question 14

The control system consist of what 3 parts?

Answer 14

controller (within brainstem)

effectors (lungs and respiratory muscles)

feedback (chemo and mechanoreceptors)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Carotid chemoreceptors are activated by low PaO2 and elevated PaCO2

brainstem receptors are activated by high PCO2

Question 17

What are the 2 primary roles of chemoreceptors?

Answer 17

• 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

Question 18

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

Answer 18

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