Exam #3: Control of Breathing

Question 1

How is spontaneous respiration produced?

Answer 1

Rhythmic discharge of motor neurons that innervate respiratory muscles

Question 2

What controls the discharge of the motor neurons responsible for respiration?

Answer 2

Chemical control:

• PCO2
• PO2
• H+

Question 3

Where is the automatic control of respiration located?

Answer 3

Pons & medulla

Question 4

Where is the voluntary control system of respiration located?

Answer 4

Cerebral cortex

Question 5

What are the key controlling factors of respiration?

Answer 5

Increased PCO2*
Decreased PO2
Decreased pH

Question 6

Draw the pathways that control breathing.

Answer 6

N/A

Question 7

What are the non-chemical influences that control breathing?

Answer 7

Chest wall
Diaphragm
Conducting airway

Changes here sends signals directly to the spinal cord to alter breathing e.g. during exercise

Question 8

What is the most important controlling factor of respiration?

Answer 8

Changes in PCO2

*Stronger effect than changes in pH

Question 9

Can the partial pressure of oxygen change the respiratory rate independent of CO2?

Answer 9

Yes

Question 10

In what range is the chemoreceptor system the most sensitive to changes in PO2?

Answer 10

30 - 60 mmHg

Question 11

How does the effect of PCO2 & H+ compare in the control of respiration?

Answer 11

Changes in blood H+ have considerably less effect in stimulating chemosensitive neurons

Question 12

Where are the peripheral chemoreceptors that detect changes in PO2?

Answer 12

Aorctic bodies
Carotid bodies

*Note that these respond to changes in CO2 & H+ to a lesser extent than oxygen

Question 13

Where are the central respiratory chemoreceptors located?

Answer 13

In a “chemosensitive area” that lies just beneath the medulla

3 regions:

1) Rostral (Mitchell)
2) Intermediate (Schlafke)
3) Caudal (Loeschcke)

Question 14

Where is the sensory integration center for impulses from peripheral chemoreceptors, baroreceptors, & other pulmonary receptors.

Answer 14

NTS

Question 15

What are the four nuclei of the respiratory center?

Answer 15

1) DRG= Dorsal Respiratory Group
2) VRG= Ventral Respiratory Group
3) PRG= Pneumotaxic Respiratory Group
4) Pre-Botzinger complex

Question 16

What is the function of the Pre-Botzinger complex?

Answer 16

Rhythmic respiration

*Note this is like the SA node in the heart.

Question 17

Where do signals from the Pre-Botzinger complex go?

Answer 17

DRG

Question 18

What is the function of the DRG?

Answer 18

Sends out repetitive bursts of inspiratory neuronal action potentials

Question 19

What is the function of the PRG?

Answer 19

• Transmits signals to the inspiratory area (DRG)
• Switches off the DRG

*Primarily controls rate & depth of breathing

Question 20

What is the function of the VRG?

Answer 20

• Inactive during normal respiration
• Increased stimulation results in spill over from the DRG
• DRG spillover recruits the VRG for active breathing (both inspiration & expiration)

Question 21

How is respiration regulated during exercise?

Answer 21

Voluntary component added to the automatic component

Question 22

What are irritant receptors?

Answer 22

Receptors that are stimulated to edema, toxic substances, smoking…etc.

Question 23

What is the function of irritant receptors?

Answer 23

Causing coughing & sneezing

Note that these may also cause bronchial constriction in asthma & emphysema

Question 24

What are J receptors?

Answer 24

Sensory nerves located in the alveolar walls, in juxtaposition to the pulmonary capillaries

Question 25

What stimulates J receptors?

Answer 25

• Pulmonary capillary engorgement or pulmonary edema

- Gives a feeling of dyspnea

Question 26

What is the effect of brain edema on respiration? How is it treated?

Answer 26

• Depressed respiration

- Hypertonic solutions e.g. mannitol

Question 27

What reflex is initiated by the stretch receptors?

Answer 27

Hering-Breuer inflation reflex

• Located in the muscular portions of the bronchi & bronchioles
• Transmits signals to the DRG when the lungs are overstretched
• Switch off inspiratory ramp & increases the rate of respiration

Note that this normally does not happen until VT= 3x normal

Question 28

What is the Hering-Breuer inflation reflex?

Answer 28

• Switch off inspiratory ramp in cases of overstretching of the lung parenchyma

Question 29

What are Kussmaul’s respiration’s an indication of?

Answer 29

Metabolic acidosis

• Relentless, rapid, & deep breathing

Question 30

What are Cheyne-Stoke’s respiration’s an indication of?

Answer 30

Stroke
Encephalopathies
Heart Failure

Ventilatory oscillations with long cycle times

Question 31

What is Biot’s breathing an indication of?

Answer 31

Medullary trauma
Stroke

• Quick, shallow inspirations followed by regular or irregular periods of apnea

Question 32

Draw the diagrams of Kussmaul’s, Cheyne-Stokes, & Biot breathing patterns.

Answer 32

N/A

Question 33

Describe the reciprocal innervation of the respiratory muscles.

Answer 33

Active inspiratory muscles= inhibited expiratory muscles & vice versa

Question 34

What do the central chemoreceptors respond most to? What do the peripheral chemoreceptors respond most to?

Answer 34

PCO2 & PO2 respectively