DECEREBRATION

From Big Medical Encyclopedia

DECEREBRATION (decerebratio; lat. the de-prefix extraction, destruction + cerebrum a brain) — removal of front department of a brain. This operation is applied on the highest vertebrate animals to studying of activity of c. N of page without participation of big cerebral hemispheres and a diencephalon.

For the first time D. was applied in 1896 by Ch. Sherrington. Section of a trunk of a brain is made ahead of tentorium cerebelli on front border a chetverokholmiya. At the same time also front hills are usually removed or damaged. After operation on a measure of weakening of an anesthesia in extremities and in all body the so-called cerebrate rigidity — reduction of group of the muscles holding an organism from falling develops (generally extensors); their antagonists at the same time relax. As a result all extremities are unbent and convulsively extended, the head and a neck rise up, the tail is unbent there and the spine is curved. The similar effect is observed at the termination of blood circulation in the forefront of a brain by bandaging of carotid arteries and a basilar artery in the field of the brain (varoliyev) bridge.

The irritation of musculocutaneous receptors causes strengthening of reaction, and bendings caused by this irritation defensive reflex and a chesatelny reflex are shown in the weakened look. Eventually the detserebratsionny extensive tone weakens; it can even disappear and be replaced with the general flexion tone.

The Detserebratsionny tone is caused by simultaneous emergence of numerous labyrinth and cervical tonic reflexes. The coordinating devices of these reflexes — predoor (vestibular) kernels in a myelencephalon and cervical segments of a spinal cord — are under the continuous braking influence from a reticular formation oblong and a mesencephalon (see. Reticular formation ). It is supposed that at D. there is a break of the central routes going from some kernels of subcrustal educations to the braking department of a reticular formation owing to what the tonic centers of an oblong and spinal cord are exempted from the braking influences. Under the influence of the constant exciting impulsation from other departments of a reticular formation, and also from labyrinth and muscle receptors these tonic centers come to an active state, a cut is shown by a cerebrate rigidity.

The cerebellum also has the braking effect on the tonic centers — through a kernel of a tent and the braking department of a reticular formation. Therefore removal of a cerebellum leads to strengthening cerebrate rigidity (see).

If section of a brainstem occurs ahead of red kernels, the cerebrate rigidity does not develop. It occurs because in such cases the braking department of setevidny formation of a myelencephalon tests the constant regulating impulsation from red kernels and other formations of the same level.

If section of a brainstem occurs behind predoor kernels of a myelencephalon owing to what drops out and the facilitating action of setevidny education, all muscles of a skeleton become weakened, deprived of a tone.

On the decerebrated animals — rabbits, cats and dogs — the main consistent patterns of inborn reflex activity were determined: coordinate activity of antagonistic muscles during defensive reflexes of bending and extension, tonic reflexes and attitudinal reflexes, phase reflexes of hackling, pacing etc.

See also Brain .

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