Nervous control of respiratory
Nerve impulses from the respiratory centre in the medulla oblongata result in contraction
of the diaphragm and external intercostal muscles.
The diaphragm is controlled by the phrenic nerve which leaves the spinal cord at C3,C4and C5
The intercostal muscles are controlled by the intercostal nerves which leave the spinal cord
at T1 through to T12.
Medullary rhythmicity centre located in the medulla oblongata, consists of the inspiratory and
expiratory neurons which control the basic rhythm of breathing.
Inspiration lasts 2 seconds.
Expiration lasts 3 seconds.
During normal quiet breathing, expiration occurs as a passive elastic recoil by the lungs.
During activity, the expiratory area sends impulses to the internal intercostal muscles and abdominal muscles to assist in expiration.
Pneumotaxic centre, located in the Pons Varolii sends impulses to the inspiratory centre to prevent overinflation of the lungs.