Control of Ventilation

Question 1

Where is the Dorsal Respiratory Group (DRG) of neurons located?

Answer 1

Medulla

Question 2

Where do DRG afferent signals come from and where does it send efferent signals?

Answer 2

Afferents: come from both mechanoreceptors and chemoreceptors, apneustic center and pneumotaxic center

Efferents: sent to spinal cord which sends signals to INSPIRATORY muscle motor neurons only

Question 3

Where is the Ventral Respiratory Group (VRG) located?

Answer 3

Medulla

Question 4

Where do VRG afferent signals come from and where does it send efferent signals?

Answer 4

Afferents: mainly come from DRG

Efferents: sent to spinal cord which signals both inspiratory AND expiratory muscle motor neurons

Question 5

Where is the Pre-Botzinger complex and what does it do?

Answer 5

Located in the medulla

-regulates respiratory pattern (pacemaker)

Question 6

Where is the apneustic center located and what is its function?

Answer 6

Pons

-prevents inhibition of inspiratory neurons (stimulates inspiration)

Question 7

Where is the pneumotaxic center located and what is its function?

Answer 7

Pons

-inhibits inspiration

Question 8

What are the 3 pulmonary receptors and how do they function?

Answer 8

1. Slowly Adapting Pulmonary Stretch Receptors(PSR)
2. Rapid Adapting PSR
3. C-fiber receptors

-all are mechanoreceptors involved in protective reflexes that send afferents to the DRG via the Vagus Nerve (CN X)

Question 9

Where are Slowly Adapting PSRs located and how do they function?

Answer 9

• Located in airway smooth muscle

- Respond to distension of the lungs by inhibiting inhalation and prolonging exhalation

Question 10

What is the Hering-Breur Reflex?

Answer 10

Inflation reflex preventing large tidal volumes. Occurs when the Slowly Adapting PSRs are stimulated. More common in infants.

Question 11

Where are Rapid Adapting PSRs located and how do they function?

Answer 11

Located between airway epithelial cells

• respond to noxious gases, cigarette smoke, dust
• involved in coughing reflex, mucous production, bronchoconstriction

Question 12

Where are the C-fiber receptors located and how do they function?

Answer 12

Located in alveoli and conducting airways next to the capillaries (Juxtacapillary Receptors).

• respond to lung injury or overinflation (either chemical or mechanical)
• involved in initiating slow shallow breathing

Question 13

What are the two peripheral chemoreceptors?

Answer 13

Carotid and Aortic Bodies

Question 14

2 metabolites monitored by the peripheral chemoreceptors.

Answer 14

1. O2
2. H+
   - CO2 (very minor)

Question 15

Where are the central chemoreceptors located?

Answer 15

Medulla

Question 16

Main metabolite monitored by the central chemoreceptors.

Answer 16

CO2

• indirectly monitored
• CO2 crosses BBB and increases the concentration of H+ (lower pH)
• chemoreceptors respond to the lower pH

Question 17

Small fluctuations in CO2 concentration have large effects on ventilation in both depth and rate. Why does oxygen fluctuation NOT have as big of an influence?

Answer 17

Hb saturation remains high for a wide range of O2 pressures. Only when the O2 pressure falls below 60mmHg and Hb oxygen saturation falls below 90% does ventilation change.

Question 18

What is the major regulator of ventilation at high altitude.

Answer 18

O2 pressure

Question 19

Why does breathing at a higher altitude often result in respiratory alkalosis?

Answer 19

The lower pressure of Oxygen that is inhaled results in increased respiratory rate which expels more CO2 resulting in an increased pH.

Question 20

What are the two mechanisms to compensate for the respiratory alkalosis caused at high altitude?

Answer 20

1. Renal Compensation: kidneys secrete more bicarb

2. CSF Compensation: CSF transport bicarb out into systemic circulation