32 Control of Breathing

Question 1

What 3 substances are synergistic in stimulating respiration?

Answer 1

Hypercapnia, hypoxia, acidemia

Question 2

What substance is most significant in control of respiration?

Answer 2

CO2 (thru central chemoreceptors)

Question 3

T/F pH, pCO2, PO2 levels physiologically adjust during exercise?

Answer 3

False. They are held constant.

Question 4

T/F Speech and swallowing present a real problem for respiratory control.

Answer 4

False.They are handled perfectly.

Question 5

What nerve transmits the Central Pattern Generator’s (CPG) signal?

Answer 5

Spinal motor neurons

Question 6

Where are the nuclei located of the spinal motor neurons that transmit the CPG signal?

Answer 6

C3-5

-“keeps the diaphragm alive”

Question 7

At what level is the CPG located?

Answer 7

Medulla

Question 8

If you lesioned the medulla mid-sagittally, what would happen to breathing?

Answer 8

CPG signal would continue to be generated independently on each side

Question 9

Pontomedullary transection would do what to breathing?

Answer 9

Nothing

Question 10

Spinomedullary transection would do what to breathing?

Answer 10

Tongue would keep moving for breath but you would not breathe.

Question 11

Where is the cell body for External intercostal muscles?

Answer 11

-Thoracic ventral horn (so think if you lesioned all thoracid levels, “chest” inspiration would be difficult, but diaphragm inspiration would continue)

Question 12

Where is the cell body for diaphragm?

Answer 12

-Ventral horn C3-5

Question 13

What are the secondary musceles of inspiration?

Answer 13

-Larynx & pharynx (nuc. ambiguus), tongue, sternocleidomastoid, trapezius, nares

Question 14

Internal intercostals have what function?

Answer 14

Expiration

Question 15

Where are the nuclei located for secondary muscles of expiration?

Answer 15

• Int. intercostal:thoracic ventral horn

- abdominal: lumbar ventral horn

Question 16

What is eupnea?

Answer 16

Resting/mild exercising breath pattern

Question 17

T/F expiratory muscles are active during mild exercise?

Answer 17

False (but yes for intense exercise)

Question 18

Dorsal Respiratory Group and Ventral Respiratory Group each have what function?

Answer 18

• DRG: Integrates chemoreceptor,stretch, airway, and irritant sensory input (via CN IX & X). Closely associate w/ Nuc. Tractus Solitarius. Has pre-motor & internurons but no motor neurons.
• VRG: the Do-er. Motor nuerons for both inspire and expire. Its sensory info comes from the DRG.

Question 19

Where is the CPG maybe located?

Answer 19

• Maybe Pre-Botzinger complex (in rostral VRG).
• Or location changes throughout the day.
• Or it is “emergent” from a network.

Question 20

The pons has what two respiratory neuron groups?

Answer 20

• Apneustic center
• Pneumotaxic center
• (These modulate respiratory activity)

Question 21

T/F Peripheral chemoreceptors under normal circumstances help keep O2 levels normal.

Answer 21

False. Emergency only.

Question 22

Where are peripheral chemoreceptors located?

Answer 22

Carotid and aortic bodies.

Question 23

What 3 things are important to the function of peripheral chemoreceptors?

Answer 23

• Close to lung (rapidly detect changes)
• Highly vascular (similar chemo concentration to systemic blood)
• Both sympa and parasympa input. (therefore autonomic input affects their response)

Question 24

What are carotid body cells called?

Answer 24

glomus (chemosensitive) cells and sustentacular cells (supportive)

Question 25

What is the mechanism of peripheral chemoreceptor activation?

Answer 25

• Down O2, or up CO2/acid
• Inhibit K+ channels
• Depolarize
• Ca++ channels open
• Neurotransmitter releases

Question 26

How do changes in CO2/acid affect glomus cells?

Answer 26

• Mostly make them more sensitive to O2 levels

- Activate them a bit

Question 27

-T/F CO2 readily crosses the Blood Brain Barrier (BBB) from blood into brain?

Answer 27

True

Question 28

T/F chemoreceptors respond to CO2 and acid in the same way?

Answer 28

False. It responds less to “other” acids than it does to physiological acidity from CO2.

Question 29

Active transport of HCO3 from blood into CSF would have what effect on central chemoreceptors?

Answer 29

-They would normalize at a new baseline (occurs in chronic hypercapnia. The kidney also increases serum HCO3 during chronic hypercapnia, reducing drive to breathe and normalizing pH)

Question 30

What is a medical condition wherin chronic hypercapnia would occur?

Answer 30

COPD

Question 31

Where are central chemoreceptors located? What is their neurotransmitter?

Answer 31

• Distributed thru medulla. (especially raphe and ventrolateral medulla)
• Serotonin (SIDS cause maybe?)

Question 32

If central chemoreceptors are in medulla, what are the serotonergic cells in midbrain doing to them??

Answer 32

-Mediating arousal response to CO2

Question 33

How much of CO2 response is due to central chemoreceptors?

Answer 33

80-90% (the peripheral chemoreceptors are faster to sense/respond to CO2 changes. The “First Line.”)

Question 34

Pulmonary stretch receptors in muscle layer are fast-adapting or slow?

Answer 34

Slow. (they tell how inflated the lung is)

Question 35

Pulmonary stretch receptors adjacent to airway epithelium are fast-adapting or slow?

Answer 35

Fast. (the tell us irritants are present) So, smoke a cigarette and you will quickly adapt and not notice how terrible it is.

Question 36

What do C-fiber receptors in the lung interstitium and alveolar walls do?

Answer 36

• React to chem/mech. stimuli to produce…
• Bronchoconstriction, secretion of mucus, rapid shallow breathing. Stop your inhaled oreo cookie from getting into deeper lung areas.

Question 37

During wakefulness, (aside from CPG), what provides a tonic drive to breathe?

Answer 37

Reticular activating system

Question 38

What can the limbic system do to breathing?

Answer 38

Produce sudden sharp inspiration

Question 39

What are the two kinds of sleep apnea?

Answer 39

• Obstructive (airway dilator activity drops)

- Central (depress response to CO2 & depressed reticular activating system)

Question 40

What happens to a neuromuscular disease patient who goes to sleep?

Answer 40

Gas exchange worsens. also occurs in lung disease.

Question 41

What will happen to pleural pressure during obstructive sleep apnea?

Answer 41

Get stronger and stronger

Question 42

What amount of increase does exercise have on the following things? A)O2 consumption B)cardiac output C)minute ventilation D) oxygen extraction

Answer 42

A)15x
B)5x
C)10x
D)3x

Question 43

T/F Breathing control is achieved solely by central and peripheral chemoreceptors?

Answer 43

False. Also ergoreceptors, proprioreceptors, collateral input. These provide ANTICIPATORY input.