L29. Generation and Control of Rhythmic Breathing

Question 1

Generation of rhythmic breathing - involuntary control - inspiration?

Answer 1

• The respiratory muscles, which are skeletal muscles, do not contract spontaneously
• Our rhythmic breathing is generated involuntarily in the respiratory centres in the medulla oblongata (also cardiovascular (CVS) centre)
• The neurons in the inspiratory centre spontaneously discharge
• When discharging, they initiate action potentials in the motor neurons to the inspiratory muscles and induce muscle contraction
• The spontaneous discharge of the inspiratory centre is limited in duration and it soon ceases (at end of inspiration)

Question 2

Involuntary control - expiratory centre?

Answer 2

• Neurons in the expiratory centre are normally quiescent; they do not discharge spontaneously
• Thus, when the inspiratory centre stops firing contraction stops and the inspiratory muscles relax
• Expiration occurs passively due to the elastic recoil of the lungs
• During forced expiration/exercise/disease: the expiratory centre fires to activate expiratory muscles