ASCENDING PATHWAYS ENDING IN THE BRAINSTEM
A number of tracts arising in spinal grey matter, and ending in masses of grey matter in the brainstem, are described. Some of them are as follows.
Spinoreticular fibres begin from spinal neurons mainly in lamina VII (also V and VIII). The fibres are partly crossed and partly uncrossed. The fibres ascend in the ventrolateral part of the spinal cord,intermingling with spinothalamic tracts. They end in the reticular formation of the medulla and pons. The tract probably carries pain.
The spino-olivary tract is also a crossed tract. It lies at the junction of the anterior and lateral funiculi of the spinal cord. The fibres of the tract end in accessory olivary nuclei.
A number of tracts travel from spinal cord to different areas in the midbrain. They are collectively referred to as spinomesencephalic tracts.
The spinotectal tract connects the spinal grey matter to the superior colliculus. It is a crossed tract. It carries impulses that regulate reflex movements of the head and eyes in response to stimulation of some parts of the body. According to some authorities the tract may carry sensations of pain and temperature. Other spinal fibres reach the pretectal nuclei, and some nuclei in the reticular formation of the midbrain. Spinal cells projecting to the midbrain are located mainly in lamina I. They also lie in laminae IV to VII. Most of the fibres cross the midline and ascend in the anterior part of the spinal cord. Painful stimuli may pass through these fibres.
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