voice & speech: journey of the voice: respiration: nervous system

The Nervous System & Its Signals to Breathe

The respiratory centre of the brain regulates involuntary breathing so that the concentration of O2 and CO2 remain constant. There are three stimuli that affect the respiratory centre

• CO₂ in the blood stream: affects the respiratory centre directly. Though a lack of oxygen will also affect the centre, it is more sensitive to carbon dioxide.

• response of the chemoreceptors: located in two centres, the carotid and aortic bodies, just above the heart, the chemoreceptors respond to the chemical makeup of the bloodstream as it flows through minute arteries coming off the major blood vessels. When the CO₂ level rises to a certain level, it sends a signal to the brain, which in turns sends a signal to the diaphragm and to the intercostals. Once the inspiration is completed, the O₂ level rises, and the muscles relax. The CO₂ laden air is pushed out of the lungs by passive forces, and the process begins again, happening about 12 times a minute for our whole lives.

• activity of the stretch receptors: located in the lung tissue, bronchial tree and the visceral pleura, these respond to the amount of stretch in the lung tissue. When the lungs are relaxed (deflated), few impulses from the stretch receptors are sent to inspiratory centre of the brain. When they are expanded, impulses are relayed at high-frequency to the expiratory centre of the brain, which inhibit the inhalation process. Overexpansion of the lungs is also inhibited by receptors located in the bronchioles. When the receptors are relaxed, the signals are inhibited, allowing the inhalation process to begin again.

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  Back to Respiration

  • More on Anatomy
  • The Physics of Breathing
  • Application to the Performer