Localisation of the respiratory centre:- The
respiratory centre, which is constituted by the
integration of many neurons, has been localised .
in e relatively extensive area between the upper
border of the pons and the lower third or so of
the medulla oblongata. It has been demonstrated
by V. E. Henderson and Craigie, by Gesell, Bricker
and Magee that these neurons are scattered at different
levels through the formatio reticularis of
the se parts of the brain stern. The centre is
bilateral and each half contains inspiratory and
expiratory components that control muscles of inspiration
and expiration respectively.
The nervous structures controlling respiration
has been localised by Markwald. The fact that
powerful and prolonged tonic inspiratory movements
supervened after bilateral section of the vagus
nerves and division of the brain stem immediately
behind the posterior colliculi, made him conclude
that a centre inhibitory to respiration was located
in the posterior colliculi.
Tine vagi however also has an inhibitory action,
consequently these inspiratory movements, or "cramps",
as he termed them, appeared only after their influence
had been abolished as well. In recent years
Lumsden found that prolonged inspiratory movements
occurred only if the section passed through the pons
e few millimetres behind its anterior border, and
occurred whether the vági were divided or not, and .
that these respiratory movements were dependent upon
an apneustic or inspiratory centre situated at the
level of the striae accousticae, which was dominated
normally by an inhibitory or pneumotoxic centre situated
'i.n the upper part of the pons. On account of the inhibitory
influence of the latter, the apneustic n-ovements
were transformed into the rhythmical movements
characteristic of normal respiration, as shown by
the fact that rythmic action currents are registered
by leads from the medulla. Section of the brain
stem behind the atriae accousticae brought about a
series of gasps occurring at relatively long intervals.