Figure 10.9 The respiratory cycle.

Copyright © 2009 Pearson Education, Inc.

Figure 10.9 The respiratory cycle.

Regulation of Breathing

Figure 10.13

• Respiratory centers in the pons and medulla oblongata control both the rate of respiration and the inspiratory depth.

• Higher brain centers, in the cerebrum, have conscious control, and can modify breathing.

• Medulla oblongata: sensitive to hydrogen ions (pH) in cerebrospinal fluid resulting from carbon dioxide in blood

• Carotid and aortic bodies: sensitive to oxygen and hydrogen ion (pH) levels

Regulation of Breathing

Carbon dioxide & pH

• Carbon dioxide is a waste product in exhaled air

• Forms an acid in water:

CO2 + H2O carbonic acid (H2CO3)

H2CO3 bicarbonate (HCO3-) + hydrogen ion (H+)

• pH is a measure of the hydrogen ion concentration

• The carbonic acid–bicarbonate buffer system (like all buffers) resists pH changes.

• If H+ concentrations in blood begin to rise, excess H+ is removed by combining with HCO3

– .

• If hydrogen ion concentrations begin to drop, H2CO3 dissociates, releasing H+

The bicarbonate buffer system in blood


Figure 10.12 oxygen transport in blood.


Figure 10.12 carbon dioxide transport in blood.


Figure 10.10a Measurement of lung capacity.

Respiratory Volumes• Tidal volume (TV) – air that moves into and out

of the lungs with each breath (approximately 500 ml)

• Inspiratory reserve volume (IRV) – air that can be inspired forcibly beyond the tidal volume (2100–3200ml)

• Expiratory reserve volume (ERV) – air that can be evacuated from the lungs after a tidal expiration (1000-1200ml)

• Residual volume (RV) – air left in the lungs after strenuous expiration (1200ml)

Respiratory Capacities

• Vital capacity (VC) – the total amount of air that can be taken in by the deepest expiration followed by the deepest inspiration

= TV + ERV + IRV

• Total lung capacity (TLC) – sum of all lung volumes = VC + Residual Volume (approximately 6000 ml in males)

Other Pulmonary Function Tests

• Forced vital capacity (FVC) – gas forcibly & rapidly expelled after taking a deep breath

• Forced expiratory volume (FEV = peak flow) – the amount of gas expelled during specific time intervals (usually 1 sec)


Figure 10.11 Partial pressures. (1 of 3)

Figure 10.9 The respiratory cycle.

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Transcript of Figure 10.9 The respiratory cycle.