Respiratory System Lecture 2

Question 1

What is included in the Medullary Respiratory Center (MRC)? (3)

Answer 1

1. Pre-Bötzinger complex
   - “pacemaker” sending signal to DRG to initiate breathing pattern
2. Dorsal respiratory group (DRG)
   - inspiratory neurons
3. Ventral respiratory group (VRG)
   - inspiratory and expiratory neurons

Question 2

How do the DRG inspiratory neurons work?

Answer 2

DRG inspiratory neurons:
* Cycling between active and inactive.
* Gives resting breathing (if 5 seconds: breathing frequency = 12 bpm or breathes per minute; typical resting breathing frequency 6 – 16 bpm)

Question 3

What occurs when the DRG Inspiratory neurons are active?

Answer 3

• 2 seconds
• diaphragm/external intercostal contract
• resting inspiration

Question 4

What occurs when the DRG Inspiratory neurons are inactive?

Answer 4

• 3 seconds
• diaphragm/external intercostal recoil
• resting expiration

Question 5

What drugs can suppress DRG inspiratory
neurons?

Answer 5

Morphine, barbiturates, fentanyl, and heroin can suppress DRG inspiratory neurons

overdose deaths often involve breathing stopping)

Question 6

How is inspiration/expiration affected when the Internal Neurons of the DRG are ACTIVE?
(3 different pathways)

Answer 6

The diaphragm and external intercostals have a stronger contraction which leads to more forceful inspiration

They can be activated along with the Inspiratory Neurons of the VRG to contract the inspiratory accessory muscles to create a more forceful Inspiration

They can also be activated along with the Expiratory Neurons of the VRG to contract the accessory muscles of expiration and cause a more forceful Expiration

Question 7

How is inspiration/expiration affected when the Internal Neurons of the DRG are INACTIVE? (1 pathway)

Answer 7

the diaphragm and external intercostals have a stronger recoil and cause a more forceful expiration.

Question 8

When is the ventral respiratory group recruited?

Answer 8

At a certain breathing, we need to also recruit ventral respiratory group (VRG).

Provides active/inactive cycling of inspiratory/expiratory neurons to accessory muscles of inspiration and expiration

Question 9

What is the Pontine respiratory group?
How does it work?

Answer 9

Pontine respiratory group
- In pons.
- Provides input to DRG.

Exactly how it works?
- Influence especially seen during activities like swimming and speaking.
- Likely effects switch between active and inactive in DRG

Question 10

What are Mechanoreceptors?
What are the 2* Types?

Answer 10

Mechanoreceptors –
detect mechanical changes.
- Proprioceptors
- Slow adapting

Question 11

What are proprioceptors?

Answer 11

• In joints and muscles.
• Respond to changes in body movement (rest to exercise).
• Function: match ventilation to movement needs; input to DRG and likely involved in when to recruit VRG for more forceful breathing

Question 12

What are Slow Adapting Mechanoreceptors?

Answer 12

• In smooth muscle surrounding airways.
• Contribute to Hering-Breuer reflex – end inspiration by switching DRG from active to inactive if lung volume gets too large.
• Protective function: prevents overexpansion damaging lung tissues.

Question 13

What are Chemoreceptors?
What are the 2* Types?

Answer 13

Chemoreceptors – detect chemical changes.
- Peripheral chemoreceptors:
- Central chemoreceptors:

Question 14

What are Peripheral Chemoreceptors?

Answer 14

• In carotid sinus and aortic arch (same locations as arterial baroreceptors).
• detect changes in blood oxygen, carbon dioxide, and pH levels to regulate respiration and maintain homeostasis.

Question 15

What are Central chemoreceptors?

Answer 15

• In medulla oblongata.
• Respond to changes in brain extracellular fluid.
• monitor changes in cerebrospinal fluid pH and indirectly control respiration by regulating the levels of carbon dioxide in the bloodstream.

Question 16

How is the cycling of DRG Neurons affected by Increased Activity? (NON-CO2) (5)

Answer 16

As Activity Increases,
Non-CO2 acids like lactate increase,
which increases the [H+] concentration
The Firing of Peripheral Chemoreceptors Increases,

Results in an Increased Cycle of the Active/Inactive DRG Inspiratory Neurons and an increase in Ventilation.

Question 17

How is the cycling of DRG Neurons affected by Increased Activity? (CO2) (5)

Answer 17

As Activity Increases,
Brain Extracellular and Arterial P-CO2 Increase
Brain Extracellular and Arterial [H+] increase
The Firing of Central AND Peripheral Chemoreceptors Increases,

Results in an Increased Cycle of the Active/Inactive DRG Inspiratory Neurons

Question 18

How is the cycling of DRG Neurons affected by High-Altitude? (3)

Answer 18

When Altitude increases,
Arterial PO2 decreases,
The Firing of Peripheral Chemoreceptors Increases,

Results in an Increased Cycle of the Active/Inactive DRG Inspiratory Neurons

Question 19

What is the Hering-Breuer reflex?

Answer 19

tells you to end inspiration when it gets too large

Question 20

What is Apnea?

Answer 20

Apnea – voluntarily stopping breathing.

Have a limited ability to over ride involuntary breathing

Apnea is a temporary cessation of breathing, particularly during sleep, characterized by the absence of airflow in and out of the lungs.

Question 21

Critical levels:

Answer 21

• Decrease arterial oxygen enough – unconsciousness and involuntary breathing should resume.
• Increase arterial CO2 enough – involuntary breathing starts.