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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.
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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
Copyright © 2009 Pearson Education, Inc.
Figure 10.12 oxygen transport in blood.
Copyright © 2009 Pearson Education, Inc.
Figure 10.12 carbon dioxide transport in blood.
Copyright © 2009 Pearson Education, Inc.
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Figure 10.10a Measurement of lung capacity.
Copyright © 2009 Pearson Education, Inc.
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)
Copyright © 2009 Pearson Education, Inc.
Figure 10.11 Partial pressures. (1 of 3)
