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Flashcards in Control of Respiration Deck (24):
1

In diffusion diseases (e.g. interstitial disease), what is the change in...

PaO2?

SaO2?

PaCO2?

A-a gradient?

PaO2 goes down

SaO2 goes down

PaCO2 stays the same

A-a gradient increases

2

In V/Q mismatch diseases (e.g. moderate COPD), what is the change in...

PaO2?

SaO2?

PaCO2?

A-a gradient?

PaO2 goes down

SaO2 goes down

PaCO2 stays the same

A-a gradient increases

3

In diseases with shunts (e.g. pneumonia), what is the change in...

PaO2?

SaO2?

PaCO2?

A-a gradient?

PaO2 goes down

SaO2 goes down

PaCO2 stays the same

A-a gradient increases

4

In low [Hb], what is the change in...

PaO2?

SaO2?

PaCO2?

A-a gradient?

PaO2 stays the same

SaO2 stays the same

PaCO2 stays the same

A-a stays the same

5

In CO poisoning, what is the change in...

PaO2?

SaO2?

PaCO2?

A-a gradient?

PaO2 stays the same

SaO2 decreases

PaCO2 stays the same

A-a stays the same

6

Where is the respiratory center in the brain?

Medulla

7

The medulla, the respiratory center of the brain, controls motor neurons that control respiratory muscles. Which two parameters can be changed by this control?

1. Tidal volume

2. Breathing rate

8

Where are peripheral chemoreceptors located?

Carotid bodies (on type 1, or glomus cells)

They are located in the carotid artery.

9

Peripheral chemoreceptors increase ventilation in response to what 3 signals?

1. Low arterial O(relatively insensitive until PaO2 is less than 55 torr)

2. High arterial PCO2 (very fast acting, within seconds)

3. High arterial [H+] (also fast acting; they are the only mediator of response to metabolic acid base insults)

10

Which peripheral chemoreceptor type mediates an increase in ventilation in response to metabolic acid-base insults?

The high arterial [H+] receptors

11

True or False: The peripheral chemoreceptors that detect low arterial O2 linearly regulate PaO2 vs. ventilation rate.

False. The regulation is depicted as a curve that is quite flat until it reaches about 55 torr. PaO2 levels that fall under 55 torr trigger the greatest responses in the peripheral chemoreceptors to increase ventilation rate.

12

Where are central chemoreceptors located?

Located on the ventral surface of the medulla

13

What do central chemoreceptors detect and how do they do it?

The central chemoreceptors are on the ventral surface of the medulla and they detect H+ levels. However, between the central chemoreceptors and the capillaries is the blood-brain barrier which is impermeable/poorly permeable to charged species. This makes it so the central chemoreceptors can't detect the H+ in the capillaries. Instead, the capillaries have CO2 that freely diffuses across the blood-brain barrier into the cerebral spinal fluid. There is carbonic anhydrase enzyme in the cerebral spinal fluid which turns H2O and CO2 into H2CO3 which turns into H+ and HCO3-. It's these free H+ that result from this reaction that the central chemoreceptors detect. Through binding to protons in the CSF, the central chemoreceptors can sense the arterial CO2.

14

How quickly do central chemoreceptors react to changes in CO2?

Response is quite slow (takes minutes). This is because it takes time for CO2 to cross the blood brain barrier and for the bicarbonate buffer system reaction to occur.

15

True or False: The peripheral chemoreceptors are the most important day-to-day regulators of ventilation.

FALSE. The most important day-to-day regulators of ventilation are the central chemoreceptors.

16

Do central or peripheral chemoreceptors mediate the majority of the ventilatory response to high PCO2 under long-term conditions?

Central

17

If you're climbing Mt. Everest, which receptor-type primarily mediates the increase in ventilation?

A. Peripheral O2 receptors

B. Peripheral CO2 receptors

C. Peripheral proton receptors

D. Central proton receptors/CO2 sensors

Peripheral O2 receptors

18

During ketoacidosis, which receptor-type primarily mediates the increase in ventilation?

A. Peripheral O2 receptors

B. Peripheral CO2 receptors

C. Peripheral proton receptors

D. Central proton receptors/CO2 sensors

Peripheral proton receptors

19

If you're climbing stairs, which receptor-type primarily mediates the increase in ventilation?

A. Peripheral O2 receptors

B. Peripheral CO2 receptors

C. Peripheral proton receptors

D. Central proton receptors/CO2 sensors

Peripheral CO2 receptors

20

If you have bronchitis, which receptor-type primarily mediates the increase in ventilation?

A. Peripheral O2 receptors

B. Peripheral CO2 receptors

C. Peripheral proton receptors

D. Central proton receptors/CO2 sensors

Central proton receptors/CO2 sensors

21

In a patient with obstructive disease (e.g. bronchitis), what 3 elements in blood could potentially mediate a compensatory increase in ventilation? Which one of these 3 is actually mediating the compensatory increase?

1. Central chemoreceptors sensing arterial CO2

2. H+ peripheral chemoreceptors

3. O2 peripheral chemoreceptors

In patients with bronchitis, the central chemoreceptors sensing arterial CO2 are the main mediator for increase in ventilation. While having a high arterial CO2 would cause an increase of H+ (due to  forward reaction of H2O + CO2 to HCO3- + H+), the H+ role in mediating the compensation is limited because it participates in the buffering in blood. The O2 peripheral chemoreceptors don't do much until PO2 drops under 55 torr

22

What are the 2 main inputs into the medulla that control respiration/ventilation? How about 5 minor inputs?

1. Peripheral chemoreceptors

2. Central chemoreceptors

3. cortex (purposefully)

4. limbic system (emotions)

5. pons

6. pulmonary irritant receptors

7. pulmonary stretch receptors

23

While the main response to high altitude is the activation of the peripheral O2 receptors to increase ventilation, explain how the other mediators respond.

A lower PIO2 will result in a lower PaO2 which will activate the peripheral O2 receptors to increase ventilation.

The increase of ventilation will increase the PaO2 but will also decrease the PaCO2. This decrease in PaCO2 will decrease the PCO2 in the CSF which decrease the H+ in the CSF which causes a decrease in ventilation. The balance of these two pathways result in a state of respiratory alkalosis (low blood PCO2 and high blood pH).

The compensation for respiratory alkalosis takes place over 2-3 days as the kidney decreases bicarbonate reabsorption (more bicarbonate being eliminated in urine). The bicarbonate decrease in the blood will cause a bicarbonate decrease in the CSF which results in more free H+ to interact with the central chemoreceptors to increase ventilation.

These things are in balance to compensate for high altitude but is never enough to reach normal PaO2 levels. This is why PaO2 in Denver is 80-85 (about 10 torr lower than at sea-level).

24

Does ventilation increase linearly with exercise?

No, it increases at a shallow slope when the ventilation increase is only triggered by a buildup of CO2 and increases at a steeper slope when the ventilation increase is also being triggered by a buildup of H+

 

 

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