PHYS: Control of Breathing

Question 1

Where is the central respiratory control center located?

Answer 1

Medulla

Question 2

The central respiratory control center is made up of synaptic connections among what three entities?

Answer 2

1) PreBotzinger complex
2) Ventral respiratory group
3) Dorsal respiratory group

Question 3

Which of the portions of the central respiratory control center is responsible for rhythm generation?

Answer 3

TRICK QUESTION!

Though the PreBotzinger complex is the main entity responsible for rhythm generation, the VRG and DRG also may have a rhythm of their own.

Question 4

What is the main role of the ventral respiratory group?

Answer 4

output to motor neurons

Question 5

What is the main role of the dorsal respiratory group?

Answer 5

receives peripheral inputs and modulates the VRG

Question 6

What are the two collections of cells in the pons that affect the activities of the medullary center?

Answer 6

1) Apneustic center (lower pons)

2) Pneumotaxic center (upper pons)

Question 7

What does the apneustic center of the pons do, and how does it do it?

Answer 7

Prolongs inspiration via affecting the excitability of medullary respiratory control nerve circuits

Question 8

What does the pneumotaxic center of the pons do, and how does it do it?

Answer 8

regulates respiratory rate (change the length of inspiration) by inhibiting the medullary inspiratory neurons

Question 9

What is the Hering Breur Reflex?

Answer 9

Negative feedback mechanism where inflation of the lungs inhibits inspiration

Question 10

How does the Hering Breur Reflex input into the respiratory control center?

Answer 10

via vagal fibers from pulmonary stretch receptors

Question 11

List the two baroreceptors that influence the respiratory control center?

Answer 11

carotid sinus

aortic baroreceptors

Question 12

How do baroreceptors work?

Answer 12

decreases in blood pressure increase ventilation

Question 13

What is the gamma-efferent input (muscle spindle system)?

Answer 13

signal to suspend inspiration and start expiration due to changes in lung compliance and airway resistance (ex. when your snorkel fills with water, you immediately blow out)

Question 14

What do irritant airway receptors do?

Answer 14

they cough in response to irritants (vagus nerve)

Question 15

What do juxtacapillary (J) receptors cause? Why?

Answer 15

The cause shallow, rapid breathing due to increased restriction to ventilation

Question 16

What controls conscious (voluntary) breathing?

Answer 16

cerebral cortex

Question 17

What do central chemoreceptors respond to (predominant minute to minute alveolar ventilation regulator)?

Answer 17

PaCO2 (pH changes of CHF)

Question 18

The partial pressure of carbon dioxide in arteries can be calculated by what equation?

Answer 18

production of CO2/alveolar ventilation

Question 19

Which has a more variable pH: Extracellular fluid in the brain or capillary blood?

Answer 19

capillary blood

Question 20

How does CO2 alter the pH of the brain?

Answer 20

1) it diffuses across the BBB
2) it undergoes the reaction into H+ and bicarbonate
3) H+ ions stimulate H+ sensitive neurons
4) these chemotaxic neurons tell the respiratory control center to increase inspiration (blow off CO2, increase pH)

Question 21

How does the bicarbonate leave the brain (eventually–when it is resetting)?

Answer 21

Bicarbonate-Cl-exchanger

Question 22

What happens to CO2 if you have severe ventilatory difficulty?

Answer 22

PaCO2 will increase, decreasing the pH of the medulla and increasing the respiratory drive

Question 23

How does the CSF pH reset in the brain?

Answer 23

after a while of increased respiratory drive, the bicarbonate in the brain will cross across the BBB which increases the brain pH and will inhibit the respiratory drive. Overall, the PaCO2 will stay increased and the pH of the CSF will be more acidic than body pH

Question 24

How do the carotid bodies work?

Answer 24

they signal Oxygen decreases, and their O2 sensitive potassium channels will be inhibited (depolarizing the cell, increasing cell excitability, and stimulating the glossopharyngeal nerves)–> increase respirations

Question 25

Do carotid bodies respond to O2 content of the blood or arterial partial pressure?

Answer 25

arterial partial pressure of oxygen

Question 26

Why is it a bad idea to give a hypoxic person 100% oxygen if they have been hypoxic/unconscious for a while (drug overdose)?

Answer 26

Their central chemoreceptors have reset, but are not responding, so the only thing keeping their respirations going are the peripheral chemoreceptors (which sense oxygen decreases). If you suddenly give them 100% oxygen, they will stop breathing!

Question 27

What is the Kussmaul respiration?

Answer 27

decreased insulin leads to increased fat breakdown and increased plasma fatty acids, so the body compensates by deep, rapid breathing to “blow off CO2” and return the pH from acidic to normal