Human Anatomy and Physiology

Control of Respiration

Alveolar ventilation Definition

AVR = frequency x tidal volume (breaths/min.) (ml/breath)

Human AVR = 4.2 L (12 x 350)

Alveolar ventilation Which factor enhances AVR more? Tidal volume

Subject Tidal volume(ml/breath)

Frequency(breaths/min)

Total ventilation(ml/min)

Dead space ventilation (ml/min)

AV(ml/min)

1

2

3

150 40 6,000 150x40=6,000 0

500

1000

12

6

6,000

6,000

150x12=1,800

150x6=900

4,200

5,100

Neural control Medullary respiratory center

dorsal respiratory group Diaphragm (inhalation)

ventral respiratory group Intercostals (in- and exhalation)

Eupnea

Early detection Types of chemoreceptors

Central (brain), not shown Peripheral (other areas)

shown

Hering-Breuer reflex

Gases in the environment CO2

Detected by central chemoreceptors Elevation of 5mm Hg, doubles AVR Increases in pCO2 : hypercapnia

O2

Detected by peripheral chemoreceptors Decline of 60mm Hg before a change is initiated Decline in pO2 : hypoxia

Mammals