VPB 121: Veterinary Physiology - II (2+1)

SPINOTHALAMIC TRACT

• The lateral and ventral Spinothalamic tracts which are present in primates, are absent in domestic animals.
• Instead these exist as a single tract concerned with tactile , thermal and pain sensations.
• The fibers project through the lateral lemniscus of the brain stem to the ventro – postero-lateral nucleus of the thalamus.
• The fibers also project through the reticular formation and central tegmental fasciculus to the intralaminar nuclei and the nucleus medialis dorsalis of the thalamus.
• In primates, the fiber system is very important for the relay of pain sensations but in domestic animals transection of this tract does not affect pin perception because pain perception continues due to the diffuseness of the propriospinal fiber which crosses and re crosses.
• Hence unilateral hemisection of the spinal cord in primate alleviates pain from contralateral lower extremity. This is not seen in domestic animals.
• Spinothalamic tracts arise from cells located in the dorsal horn in the region of the nucleus proprius of the spinal cord.