Control of breathing

Question 1

What are the 4 components to the control system in the brain that maintains breathing?

Answer 1

1. Chemoreceptors for O2 and CO2
2. Mechanoreceptors in the lung and joints
3. control centers for breathing in the brain stem
4. Respiratory muscles

Question 2

What are the control centers for breathing in the brain stem?

Answer 2

Medulla and pons

Question 3

Voluntary control of respiration can be exerted by commands from the…

Answer 3

cerebral cortex, which can temporarily override the brain stem

Question 4

The frequency of normal, involuntary breathing is controlled by three groups of neurons or “brains stem centers”. What are they?

Answer 4

1. Medullary respiratory center
2. Apneustic center
3. pneumotaxic center

Question 5

The medullary respiratory center is located in the reticular formation and is composed of two groups of neurons that are distinguished by their anatomic location. These are?

Answer 5

The inspiratory center - the dorsal respiratory group

The expiratory center - the ventral respiratory group

Question 6

Which center in the medullary respiratory center sets the basic rythym?

Answer 6

The inspiratory center, bu setting the frequency of inspiration.

Question 7

How does the inspiratory center recieve stimulus?

Answer 7

Via the glossopharyngeal nerve (CN XI) from chemoreceptors and the Vagus nerve (CN X) from mechanoreceptors.

Question 8

Where does the inspiratory center send its motor innervation?

Answer 8

To the diaphragm via the phrenic nerve

Question 9

How can inspiration be shortened?

Answer 9

By inhibition of the inspiratory center via the pneumotaxic center

Question 10

When does the expiratory center become active

Answer 10

During quiet breathing the expiratory center is inactive, with exercise, it becomes active.

Question 11

Define apneusis

Answer 11

Apneusis is an abnormal breathing pattern with prolonged inspiratory gasps, followed by brief expiratory movement.

Question 12

Where is the apneustic center? What does stimulation of this produce?

Answer 12

In the lower pons.

Stimulation produces an apneustic pattern.

Question 13

What is the function of the pneumotaxic center?

Answer 13

Turns off inspiration, limiting the burst of action potentials in the phrenic nerve.

In effect it…

1. limits the size of tidal volume
2. regulates respiratory rate

Question 14

What breathing rhythm persists in the absence of the pneumotaxic center?

Answer 14

A normal breathing Rhythm

Question 15

What allows individuals to hyperventilate or hypoventilate?

Answer 15

The cerebral cortex

Question 16

What are the most important things chemoreceptors are targeting?

Answer 16

Pa_O2, Pa_CO2 and arterial pH

Question 17

What are the most important chemoreceptors for regulating the minute to minute control of breathing?

Where are they located?

Answer 17

Central chemoreceptors

Located on the ventral surface of the medulla, near the exit point of CN X and XI.

Question 18

Brainstem chemoreceptors are exquisitely sensitive to changes in…

Answer 18

the pH of CSF.

Question 19

What do decreases in the pH of CSF produce?

Answer 19

Increases in breathing rate.

Question 20

Increases in pH of CSF cause…

Answer 20

decreases in breathing rate.

Question 21

The medullary chemoreceptors respond directly to…

and indirectly to…

Answer 21

Changes in pH of CSF

changes in arterial PCO2

Question 22

Where are peripheral chemoreceptors for O2, CO2 and H+ located?

Answer 22

In the carotid bodies at the bifurcation of the common carotid arteries and in the aortic bodies above and below the aortic arch.

Question 23

How do peripheral chemoreceptors relay information to the dorsal respiratory group (DRG)?

Answer 23

Via CN X and XI

Question 24

What impact does a decrease in arterial P_O2have on respiratory rate?

Answer 24

If the P_O2 falls below 60 mmHg, then there will be an increase in respiratory rate. Until that point there will be little response.

Question 25

What impact will an increase in arterial P_CO2 have on respiratory rate?

Answer 25

This will increase respiratory rate.

Question 26

What impact will a drop in arterial pH have on respiratory rate?

Answer 26

Increase in breathing rate.

Question 27

Where are the chemoreceptors that respond to pH in the periphery?

Answer 27

Located in the carotid bodies (NOT in the aortic bodies)

Question 28

What are five other receptors that are involved in the control of breathing?

Answer 28

1. Lung strecth receptors 2. Joint receptors 3. muscle receptors 4. irritant receptors 5. J receptors

Question 29

What are J receptors? Where are they located? How are they activated?

Answer 29

Juxtacapillary receptors, are located in the alveolar walls and near capillaries. Engorgement of pulmonary capillaries with blood and increased interstitial fluid volume may activate these receptors and increase breathing rate.

Question 30

In left sided heart failure, what receptors are activated?

Answer 30

Blood backs up into the pulmonary circulation, where J receptors mediate a change in breathing pattern, including rapid shallow breathing and dyspnea.

Question 31

Where are irritant receptors located? What happens when they fire?

Answer 31

Located between epithelial cells lining the airwars, information from these receptors travels to the medulla via CN X and causes a reflex constriction of bronchial smooth muscle and an increase in breathing rate.

Question 32

What do joint and muscle receptors detect?

Answer 32

They detect changes in the movemement of limbs and instruve the inspiratory center to increase the breathing rate. Information from the joints and muscles in important in the early (anticipatory) ventilatory response to exercise.

Question 33

What is the hering-breuer reflex?

Answer 33

A reflexive decrease in breathing rate causes by distention of lungs and airways. It works by prolonging expiratory time.