The spinoreticular tract is an ascending pathway in the white matter of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

, positioned closely to the lateral

spinothalamic tract The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory co ...

. The tract is from spinal cord—to reticular formation— to

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

. It is responsible for automatic responses to pain, such as in the case of injury.

Pathway

The spinoreticular tract utilizes four levels of neurons, unlike most ascending tracts which have first- through third-order neurons. The tract begins with first-order neurons, which immediately synapse with second-order neurons in the anterior (laminae VII and VIII) and posterior grey horns (lamina V) of the spinal column.Gray's Anatomy, 41st edition, p. 301 These neurons decussate to the opposite side (anterolateral, although in the cervical region many axons remain ipsilateral), and travel up the spinal column. It terminates in the brainstem at the medullary-pontine reticular formation. Information is sent from there to the intradmedian nucleus of the thalamic intralaminar nuclei. The thalamic intralaminar nuclei project diffusely to entire

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consistin ...

where pain reaches conscious level and promotes behavioral arousal. It is believed that spinoreticular tract projects to neurons having a large receptive fields that may cover wide areas of the body and play a role in the memory and in the affective (emotional) component of pain. It is still undetermined if the spinoreticular tract possesses ipsilateral fibers in addition to those that decussate. It is hypothesized that during development the tract was bilateral, but that the ipsilateral synapses became ineffective during development.

References

*Saladin, Kenneth S. Anatomy & Physiology: The Unity of Form and Function. New York: McGraw-Hill. 2010. *Mense, Siegfried & Gerwin, Robert D. Muscle Pain: Understanding and Mechanisms. New York: Springer. 2010. *Julien N, Goffaux P, Arsenault P, et al. Widespread pain in fibromyalgia is related to a deficit of endogenous pain inhibition. Pain 2005;114(1–2):295–302.

Pathway

References

Further reading