Respiratory System, Lecture 2

Question 1

Pre-Botzinger Complex

Answer 1

“pacemaker”
- equivalent of “SA node” (initiating a signal to give breathing)
- in medullary respiratory center on top of ventral respiratory group and to the right of dorsal respiratory group

Question 2

Dorsal Respiratory Group (DRG

Answer 2

inspiratory neurons (active/inactive)
- with these basic normal, quiet breathing
- cluster of inspiratory neurons - can be turned on and off (pacemaker giving signal)
- by turning it on and off we get our basic breathing cycle (expiration and inhalation) -> critical
- in medullary respiratory center by its one on the left, lower to the pre-botzinger complex
* morphine, barbiturates, fentanyl and heroin can suppress DRG inspiratory neurons (overdose deaths as breathing stops -> inhibit the signal that would be the typical cycle
(diagram)

Question 3

Dorsal Respiratory Group and Ventral Respiratory Group

Answer 3

dorsal respiratory group (DRG) - inspiratory neurons (active/inactive)
- can alter active/inactive to get increase in ventilation, but at a certain breathing insufficient
also in MRC - ventral respiratory group
- recruited for more forceful breathing to support increases in DRG:
‣ inspiratory and expiratory neurons of VRG recruited by DRG (both)
‣ activate accessory muscles (inspiratory and expiratory)
* hit certain intensity where on/off cycle is not enough so we recruit the ventral respiratory group (more forceful breathing)
(DIAGRAM)

Question 4

Pontine Respiratory Group (respiratory center)

Answer 4

• in pons
• provide input to DRG (signal)
• influence especially seen during activities like exercising and speaking
  exactly how it works?
• likely effects active/inactive timing in DRG

Question 5

Proprioceptors and Slow Adapting Mechanoreceptors

Answer 5

• in joints and muscles
• respond to changes in body movement (rest to maximum exercise)
• function: match ventilation to movement needs; input to DRG and likely involved in when to recruit VRG

slow adapting mechanoreceptors
- in smooth muscle surrouding airways
- contribute to Hering-Breuer reflex by responding to changes in lung volume and ending inspiration by DRG (active to inactive) if lung volume gets too large
- protective function: prevents overexpansion damaging lung tissues

Question 6

Chemoreceptors, Peripheral Chemoreceptors & Central Chemoreceptors

Answer 6

chemoreceptors:
- send input to DRG about chemical changes

peripheral chemoreceptors:
- in carotid sinus and aortic arch (same locations as arterial baroreceptors)
- respond to changes in arterial blood (Po2, non-CO2 acids, Pco2)

central chemoreceptors:
- in medulla oblongata
- respond to changes in brain extracellular fluid (Pco2) that surrounds the brain
- responding to chemical changes, just not in the blood
- monitor CO2 level

Question 7

Higher Brain Centers and Apnea

Answer 7

higher brain centers:
- input to DRG from above brainstem (mainly cerebrum and/or cerebellum)
examples
“conditioned”
- programmed patterns of breathing developed over time
apnea
- voluntarily stopped breathing
- limited ability to over ride involuntary breathing
◦ decrease oxygen to critical level: unconsciousness, involuntary breathing should resume
◦ increase CO2 to critical level: involuntary breathing starts (get ride of CO2 when expiring so when not breathing it begins accumulating)