Medial lemniscus
Encyclopedia
The medial lemniscus, also known as Reil's band or Reil's ribbon, is a pathway in the brainstem that carries sensory information from the gracile
and cuneate nuclei
to the thalamus
.
at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of the posterior column-medial lemniscus system, which transmits touch, vibration sense, as well as the pathway for proprioception.
The medial lemniscus carries axons from most of the body and synapses in the ventral posterolateral nucleus
of the thalamus
, at the level of the mamillary bodies. Sensory axons transmitting information from the head and neck via the trigeminal nerve
synapse at the ventral posteromedial nucleus
of the thalamus
.
Gracile nucleus
Located in the medulla oblongata, the gracile nucleus is one of the dorsal column nuclei that participate in the sensation of fine touch and proprioception of the lower body...
and cuneate nuclei
Cuneate nucleus
One of the dorsal column nuclei, the cuneate nucleus is a wedge-shaped nucleus in the closed part of the medulla oblongata. It contains cells that give rise to the cuneate tubercle, visible on the posterior aspect of the medulla...
to the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
.
Path
After neurons carrying proprioceptive or touch information synapseSynapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of the posterior column-medial lemniscus system, which transmits touch, vibration sense, as well as the pathway for proprioception.
The medial lemniscus carries axons from most of the body and synapses in the ventral posterolateral nucleus
Ventral posterolateral nucleus
The ventral posterolateral nucleus is a nucleus of the thalamus. Together with the ventral posteromedial nucleus , VPI and VMpo, it constitutes the ventral posterior nucleus.-Input and output:...
of the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
, at the level of the mamillary bodies. Sensory axons transmitting information from the head and neck via the trigeminal nerve
Trigeminal nerve
The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
synapse at the ventral posteromedial nucleus
Ventral posteromedial nucleus
-Inputs and outputs:It conveys information of the trigeminothalamic tract, from the solitary tract and the trigeminal nerve and projects to the postcentral gyrus....
of the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
.
Location of the medial lemniscus through the brainstem
- The cuneate and gracile nuclei reside at the closed (lower) medullaMedulla oblongataThe medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
, so the lemniscus isn't formed at this level. Fibres from these nuclei will pass to the contralateral side of the brainstem, as the internal arcuate fibres.
- At the open medulla (further up the brainstem), the medial lemniscus contains axons from the trigeminal nerveTrigeminal nerveThe trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system...
(which supplies the head region), as well as the arms and legs. It sits very close to the midline, at the same orientation of the midline, with head fibres more dorsal (closer to the back), towards the fourth ventricleFourth ventricleThe fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...
.
- By mid-ponsPonsThe pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
, the medial lemniscus has rotated. Fibres from the head are medial, fibres from the leg are lateral.
- The orientation in the midbrain is similar to that in the pons.