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A small ascending dorsal serotonergic pathway arising from the ventral and dorsal superior raphe nuclei initially travels in the DLF, with some of its fibres terminating in the periaqueductal gray of the midbrain, and the posterior hypothalamus; the majority of its fibers however pass beyond the DLF in the medial forebrain bundle, here uniting ...
Its fibers, larger than those of the gracile fasciculus, are mostly derived from the same source, viz., the posterior nerve roots. Some ascend for only a short distance in the tract, and, entering the gray matter, come into close relationship with the cells of the dorsal nucleus, while others can be traced as far as the medulla oblongata, where ...
One pathway—dorsal column–medial lemniscus pathway—begins with sensation from the periphery being sent via afferent nerve fiber of the dorsal root ganglion (first order neuron) through the spinal cord to the dorsal column nuclei (second order neuron) in the brainstem.
The spinocerebellar tracts are nerve tracts originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum. The two main tracts are the dorsal spinocerebellar tract, and the ventral spinocerebellar tract. Both of these tracts are located in the peripheral region of the lateral funiculi (white matter columns). [1]
The internal arcuate fibers are composed of axons of the gracile nucleus and the cuneate nucleus. The cell bodies of the nuclei lie contralaterally. The medial lemniscus is part of the somatosensory dorsal column–medial lemniscus pathway, which ascends in the spinal cord to the thalamus. [1]
Group C fibers include postganglionic fibers in the autonomic nervous system (ANS), and nerve fibers at the dorsal roots (IV fiber). These fibers carry sensory information. Damage or injury to nerve fibers causes neuropathic pain. Capsaicin activates C fibre vanilloid receptors, providing the burning sensation associated with chili peppers.
The fibers of this decussation are called the internal arcuate fibers and are found at the superior aspect of the closed medulla oblongata, superior to the motor decussation. Neurons of these nuclei are second-order neurons in the dorsal column–medial lemniscus pathway.
Both dorsal column nuclei contain synapses from afferent nerve fibers that have travelled in the spinal cord. [2] They then send on second-order neurons of the dorsal column–medial lemniscal pathway. Neurons of the dorsal column nuclei eventually reach the midbrain and the thalamus. [3] They send axons that form the internal arcuate fibers. [4]