1. Nervous Control of Breathing
Respiratory Center
Other aspects

2. Control of Breathing Respiratory muscles can be controlled voluntarily
Normal breathing is rhythmic and involuntary

3. Respiratory Center
Control by a group of neurons in the brainstem: the respiratory center
Medulla oblongata = “rhythmicity area”
Pons = “pneumotaxic area”
Neurons in the Medulla control the rhythm of breathing
Neurons emit impulses that signal the diaphragm and other inspiratory muscles to contract. Neurons remain inactive while expiration occurs passively
Neurons in the Pons transmit impulses to the medulla continuously and regulate the duration of inspiratory bursts (control of rate)

4. Transport of CO2
Blood in capillaries gain CO2 because body tissues contain high PCO2
The CO2 could be transported
Dissolved in blood (only~7%)
As Carbaminohemoglobin (~23%)
As HCO3- (most important form)
CO2 + H2O H2CO3 w/ aid of carbonic anhydrase
Carbonic acid dissociates:
H2CO H HCO3-

5. Chemoreceptors in the carotid and aortic bodies detect changes in the blood pH

6. Other facts about breathing
Breath test: Respiratory surfaces are so thin that certain substances other that CO2 may diffuse into the alveolar air and be expelled during breathing
A person emotionally upset may hyperventilate (become dizzy, lose consciousness , faint: alkalosis) due to low CO2 conc, and a rise in blood pH
CO may combine w/hemoglobin more effectively than O2
Ordinary air contain 0.04% CO2
Air to which additional CO2 is added is used to stimulate the rate and depth of breathing. If a person inhales air containing 4% CO2 the breathing rate usually doubles