Trigeminal lemniscus

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Trigeminal lemniscus
Lower pons horizontal KB.svg
Details
Identifiers
Latin lemniscus trigeminalis
NeuroNames 1572
TA98 A14.1.05.310
A14.1.08.680
A14.1.06.208
TA2 5862
FMA 84040
Anatomical terms of neuroanatomy

The trigeminal lemniscus or trigeminothalamic tract is a somatosensory tract containing second-order neuron fibers of the trigeminal system. It consists of the ventral and dorsal trigeminal tracts. Its second-order sensory axons convey tactile, pain, and temperature impulses from the skin of the face, the mucous membranes of the nasal and oral cavities, and the eye, as well as proprioceptive information from the facial and masticatory muscles. [1]

Contents

It terminates by synapsing with third-order neurons in the ventral posteromedial nucleus of the thalamus. [1]

This tract was historically considered a cephalic division of the medial lemniscus due to the close proximity of the two ascending tracts. [2] Like the medial lemniscus in the dorsal column-medial lemniscus pathway (DCML), that carries mechanosensory information from part of the head and the rest of the body, the trigeminal lemniscus carries mechanosensory information from the face. [1] However, the trigeminal lemniscus also carries pain and temperature sensations from the contralateral orofacial region, just as the spinothalamic tract carries these sensations from the contralateral body. Thus, the trigeminal lemniscus of the head is functionally analogous to both the DCML tracts and the spinothalamic tract of the body.

Divisions

The trigeminal lemniscus contains two main divisions:

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<span class="mw-page-title-main">Trigeminal nerve</span> Cranial nerve responsible for the faces senses and motor functions

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The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the globus pallidus. The internal capsule contains both ascending and descending axons, going to and coming from the cerebral cortex. It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.

<span class="mw-page-title-main">Spinothalamic tract</span> Sensory pathway from the skin to the thalamus

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<span class="mw-page-title-main">Dorsal column–medial lemniscus pathway</span> Sensory spinal pathway

The dorsal column–medial lemniscus pathway (DCML) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception from the skin and joints. It transmits information from the body to the primary somatosensory cortex in the postcentral gyrus of the parietal lobe of the brain. The pathway receives information from sensory receptors throughout the body, and carries this in nerve tracts in the white matter of the dorsal column of the spinal cord to the medulla, where it is continued in the medial lemniscus, on to the thalamus and relayed from there through the internal capsule and transmitted to the somatosensory cortex. The name dorsal-column medial lemniscus comes from the two structures that carry the sensory information: the dorsal columns of the spinal cord, and the medial lemniscus in the brainstem.

<span class="mw-page-title-main">Lateral lemniscus</span> Brain structure

The lateral lemniscus is a tract of axons in the brainstem that carries information about sound from the cochlear nucleus to various brainstem nuclei and ultimately the contralateral inferior colliculus of the midbrain. Three distinct, primarily inhibitory, cellular groups are located interspersed within these fibers, and are thus named the nuclei of the lateral lemniscus.

<span class="mw-page-title-main">Spinocerebellar tract</span> Nerve tract in humans

The spinocerebellar tract is a nerve tract originating in the spinal cord and terminating in the same side (ipsilateral) of the cerebellum.

<span class="mw-page-title-main">Cochlear nucleus</span> Two cranial nerve nuclei of the human brainstem

The cochlear nucleus (CN) or cochlear nuclear complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN). The ventral cochlear nucleus is unlayered whereas the dorsal cochlear nucleus is layered. Auditory nerve fibers, fibers that travel through the auditory nerve carry information from the inner ear, the cochlea, on the same side of the head, to the nerve root in the ventral cochlear nucleus. At the nerve root the fibers branch to innervate the ventral cochlear nucleus and the deep layer of the dorsal cochlear nucleus. All acoustic information thus enters the brain through the cochlear nuclei, where the processing of acoustic information begins. The outputs from the cochlear nuclei are received in higher regions of the auditory brainstem.

<span class="mw-page-title-main">Dorsal column nuclei</span> Nuclei in the dorsal column of the brainstem

In neuroanatomy, the dorsal column nuclei are a pair of nuclei in the dorsal columns in the brainstem. The name refers collectively to the cuneate nucleus and gracile nucleus, which are situated at the lower end of the medulla oblongata. Both nuclei contain second-order neurons of the dorsal column–medial lemniscus pathway, which convey fine touch and proprioceptive information from the body to the brain. The dorsal column nuclei project to the thalamus.

<span class="mw-page-title-main">Posterolateral tract</span>

The posterolateral tract is a small strand situated in relation to the tip of the posterior column close to the entrance of the posterior nerve roots. It is present throughout the spinal cord, and is most developed in the upper cervical regions.

<span class="mw-page-title-main">Sensory decussation</span> Crossing of axons between the gracile and cuneate nuclei of the brain

In neuroanatomy, the sensory decussation or decussation of the lemnisci is a decussation of axons from the gracile nucleus and cuneate nucleus, which are responsible for fine touch, vibration, proprioception and two-point discrimination of the body. The fibres of this decussation are called the internal arcuate fibres and are found at the superior aspect of the closed medulla superior to the motor decussation. It is part of the second neuron in the posterior column–medial lemniscus pathway.

<span class="mw-page-title-main">Ventral posterior nucleus</span>

The ventral posterior nucleus is the somato-sensory relay nucleus in thalamus of the brain.

<span class="mw-page-title-main">Ventral posteromedial nucleus</span>

The ventral posteromedial nucleus (VPM) is a nucleus of the thalamus and serves an analogous somatosensory relay role for the ascending trigeminothalamic tracts as its lateral neighbour the ventral posterolateral nucleus serves for dorsal column–medial lemniscus pathway 2nd-order neurons.

The spinoreticular tract is a partially decussating (crossed-over) four-neuron sensory pathway of the central nervous system. The tract transmits slow nociceptive/pain information from the spinal cord to reticular formation which in turn relays the information to the thalamus via reticulothalamic fibers as well as to other parts of the brain. Most (85%) second-order axons arising from sensory C first-order fibers ascend in the spinoreticular tract - it is consequently responsible for transmiting "slow", dull, poorly-localised pain. By projecting to the reticular activating system (RAS), the tract also mediates arousal/alertness in response to noxious stimuli. The tract is phylogenetically older than the spinothalamic ("neospinothalamic") tract.

The ventral trigeminal tract is a second-order neuron axon somatosensory tract conveying sensory information about discriminative and crude touch, conscious proprioception, pain, and temperature from the head, face, and oral cavity. The VTA arises from the spinal trigeminal nucleus and terminates in the ventral posteromedial nucleus of thalamus.

The dorsal trigeminal tract are uncrossed second-order sensory fibers conveying fine (discriminative) touch and pressure information from the dorsomedial division of principal sensory nucleus of trigeminal nerve to the ipsilateral ventral posteromedial nucleus of thalamus. Second-order fibers from the ventrolateral division of the principal sensory nucleus meanwhile cross-over to ascend contralaterally in the ventral trigeminal tract along with those fibers arising from the spinal trigeminal nucleus.

<span class="mw-page-title-main">Central tegmental tract</span> Structure in the midbrain and pons

The central tegmental tract is a structure in the midbrain and pons.

The lateral cervical nucleus is a scattered nucleus located dorsally in the lateral funiculus in the first three cervical segments of the spine. The spinocervical and spinothalamic tracts synapse in the lateral cervical nucleus; the spinocervical tract projects ipsilaterally while the spinothalamic tract projects contralaterally. The axons of neurons from the lateral cervical nucleus cross the midline, join the medial lemniscus as it forms in the caudal medulla and ascend to the ventral posterolateral nucleus.

References

  1. 1 2 3 Purves, Dale; Augustine, George J.; Fitzpatrick, David; Katz, Lawrence C.; LaMantia, Anthony-Samuel; McNamara, James O.; Williams, S. Mark (2001). "The Trigeminal Portion of the Mechanosensory System". Neuroscience. 2nd edition. Sinauer Associates. Retrieved 11 August 2024.
  2. Anthoney, TR (1993). Neuroanatomy and the neurologic exam: a thesaurus of synonyms, similar-sounding non-synonyms, and terms of variable meaning. CRC Press.

Sources

[2]

  1. Anthoney, T.R. (1993). Neuroanatomy and the neurologic exam: a thesaurus of synonyms, similar-sounding non-synonyms, and terms of variable meaning. CRC Press.
  2. Frost DO. Development of anomalous retinal projections to nonvisual thalamic nuclei in Syrian hamsters: a quantitative study. J Comp Neurol. 1986;252:95–105