L39: Control Of Breathing

Question 1

What are the 4 components that control breathing?

Answer 1

1) chemoreceptors for O2 and CO2
2) Mechanoreceptors in the lungs and joints
3) Control centers in the brain (medulla and pons)
4) Respiratory muscles regulated by brain stem receptors

Question 2

Voluntary control of breathing can be exerted via the **.

Answer 2

Cerebral cortex when breath holding or voluntary hyperventilation

Question 3

What is the ventral respiratory group?

Answer 3

-Composed of inspiratory and expiratory neurons that are inactive during normal quiet breathing , but active when demands for ventilation are increased

Question 4

What are the expiratory muscles that the ventral respiratory group stimulate?

Answer 4

Abdominals and intercostal

Question 5

What is the dorsal respiratory group (DRG)?

Answer 5

Primarily inspiratory neurons that terminate on inspiratory muscles . When they stop firing, inspiratory muscles relax and passive expiration occurs.

Question 6

What generates respiratory rhythm?

Answer 6

The pre-botzinger complex located in the upper part of the ventrolateral medulla.

Question 7

What drives the firing rate of the inspiratory neurons in the DRG?

Answer 7

The pre-botxinger complex (PBC)

-Input from peripheral chemoreceptors

Question 8

What can depress the activity of the PBC?

Answer 8

Drugs such as propofol and opioids

Question 9

Where is the pneumotaxic center and what does it do?

Answer 9

• In the upper pons
• Turns off inspiration by limiting the burst of action potentials in the phrenic nerve. Limited the size of tidal volume and regulates respiratory rate.

Question 10

What is apneusis?

Answer 10

An abnormal breathing pattern; prolonged inspiration followed by brief expiratory movement

Question 11

How does Apneusis happen?

Answer 11

Stimulation of the apneustic center neurons -> excites the inspiratory center in the medulla -> prolonged inspiration

• Prolonged APs in the phrenic nerve result in prolonged diaphragm contraction.
• Ketamine and TBI can cause this.

Question 12

What does hyperventilation mean for PaCO2 and arterial pH?

Answer 12

Decrease in PaCO2 causing arterial pH to rise.

**this is self limiting because dramatic decrease in PaCO2 causes syncope and reversion back to normal breathing

Question 13

What is the effect of hypoventilation of PO2?

Answer 13

PaO2 is decreased and PaCO2 is increased, both of which are strong drivers for ventilation.

Question 14

What do central chemoreceptors primarily sense?

Answer 14

CO2 levels- Goal is PaCO2=40

CO2 can cross BBB where it converted to H+ and HCO3+ resulting in decreased pH and chemoreceptors will HTN signal for hyperventilation

Question 15

What happens to breathing rate when pH of CSF is decreased?

Answer 15

Breathing rate is increased.

Question 16

What happens to breathing rate when the pH of the CSF is increased?

Answer 16

The breathing rate is decreased

Question 17

When is the CO2/ventilation curve shifted to the right (more CO2 is present)?

Answer 17

-during sleep, alcohol, narcotics, and anesthetics because the reticular activating system gets shut off. Ventilation does not change.

Question 18

What are the most important regulators for breathing control?

Answer 18

Central chemoreceptors

Question 19

What do peripheral chemoreceptors primarily sense?

Answer 19

O2 levels

Question 20

Where are peripheral chemoreceptors located?

Answer 20

Carotid and aortic bodies

Question 21

What do peripheral chemoreceptors do if PaO2 is <60mmHg?

Answer 21

They increase the breathing rate.

Question 22

What do peripheral chemoreceptors do when there is an increase in PaCO2?

Answer 22

Increase breathing rate, though PCs job in this is less important than its detection by central chemoreceptors

Question 23

What do peripheral chemoreceptors do when there is a decrease in arterial pH?

Answer 23

Mediated only by the PCs in the carotid bodies, but increase breathing rate.

Question 24

What kind of receptor are lung stretch receptors, where are they located, what are they activated by, and what does their activation result in?

Answer 24

• Mechanoreceptors
• Located in airway smooth muscle
• activated by distention of lungs and airway
• results in decreased breathing rate by prolonging expiration time

Question 25

What reflex prevents lung overinflation?

Answer 25

Hearing-Breuer reflex

Question 26

What kind of receptor are joint and muscle receptors, where are they located, what are they activated by, and what does their activation result in?

Answer 26

• Mechanoreceptors
• Located in joints and and muscles
• Activated by limb movement
• Results in increased breathing rate, these are important in early ventilator response to exercise

Question 27

Where are irritant receptors located, what are they activated by, and what does their activation result in?

Answer 27

• located between epithelial cells liming the airways
• Activated by noxious chemicals, dust, pollen
• results in increased breathing rate and constriction of bronchial smooth muscle

Question 28

Where are juxtacapillary receptors located, what are they activated by, and what does their activation result in?

Answer 28

• Alveolar walls
• Engorgement of pulmonary capillaries with blood
• results in increased breathing rate

Question 29

What is brief apnea?

Answer 29

• Occurs in 1/3 of normal individuals
• Episodes are less than 10 seconds
• Occurs in the lighter stages of sleep
• No effect on PaO2 and PaCO2 (because episodes are less than 10 seconds)

Question 30

What are the two types of prolonged apnea?

Answer 30

Central sleep apnea and Obstrucive sleep apnea

Question 31

What is obstructive sleep apnea?

Answer 31

• Most common apnea
• Occurs when upper airway closes during inspiration
• hundreds of episodes nightly associated with brief periods of self arousal.
• Has pleural pressure oscillations
• Most common cause is obesity

Question 32

What causes the periods of self arousal during obstructive sleep apnea?

Answer 32

Stimulation of peripheral and central chemoreceptors detecting arterial hypoxia and arterial hypercapnia (Decreased PaO2 and increased PaCO2)

Question 33

What is central sleep apnea?

Answer 33

-occurs when there is decreased ventilatory drive to the respiratory motor neurons and no respiratory effort is made (characterized by no pleural pressure oscillations)