Medial lemniscus

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Brain: Medial lemniscus
The sensory tract. (Medial lemniscus labeled at center right.)
Coronal section through mid-brain. ("e" is Portion of medial lemniscus, which runs to the lentiform nucleus and insula.)
Latin	lemniscus medialis
Gray's	subject #188 803
NeuroNames	ancil-736
Dorlands/Elsevier	l_06/12483115

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.

Path

After neurons carrying proprioceptive or touch information synapse at the gracile and cuneate nuclei, axons from secondary neurons decussate 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 axons from most of the body synapse at the ventral posterolateral nucleus of the thalamus. The axons transmitting information from the trigeminal nerve synapse at the ventral posteromedial nucleus of the thalamus.

Location of the medial lemniscus through the brainstem

• The cuneate and gracile nuclei reside at the closed (lower) 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 nerve (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 ventricle.

• By mid-pons, 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.

See also

• Posterior column-medial lemniscus pathway

Additional images

Deep dissection of brain-stem. Lateral view.	Deep dissection of brain-stem. Ventral view.	Coronal section of the pons, at its upper part.	Transverse section of mid-brain at level of inferior colliculi.
Scheme showing the course of the fibers of the lemniscus; medial lemniscus in blue, lateral in red.

External links

• Brainstem at UWisc 04NGNC
• BrainMaps at UCDavis medial lemniscus

v • d • e Brain: rhombencephalon (hindbrain)
Myelencephalon/medulla	anterior/ventral: Arcuate nucleus of medulla • Pyramid (Decussation) • Olivary body • Inferior olivary nucleus • Anterior median fissure • Ventral respiratory group posterior/dorsal: VII,IX,X: Solitary/tract • XII, X: Dorsal • IX,X,XI: Ambiguus • IX: Inferior salivatory nucleus • Gracile nucleus/Cuneate nucleus/Accessory cuneate nucleus • Area postrema • Posterior median sulcus • Dorsal respiratory group raphe/reticular: Sensory decussation • Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus) • Raphe nuclei (Obscurus, Magnus, Pallidus) tracts: Corticospinal tract (Lateral, Anterior) • Inferior cerebellar peduncle • Olivocerebellar tract • Spinocerebellar (Dorsal, Ventral) • Spinothalamic tract • PCML (Posterior external arcuate fibers, Internal arcuate fibers, Medial lemniscus) • Extrapyramidal (Rubrospinal tract, Vestibulospinal tract, Tectospinal tract)
Metencephalon/pons	anterior/ventral: Superior olivary nucleus • Basis pontis (Pontine nuclei, Middle cerebellar peduncles) posterior/dorsal: Pontine tegmentum (Trapezoid body, Superior medullary velum, Locus ceruleus, MLF, Vestibulocerebellar tract, V Principal Spinal & Motor, VI, VII, VII: Superior salivary nucleus) • VIII-c (Dorsal, Anterior)/VIII-v (Lateral, Superior, Medial, Inferior) raphe/reticular: Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus, Paramedian pontine reticular formation) • Median raphe nucleus Apneustic center • Pneumotaxic center
Metencephalon/cerebellum	Vermis • Flocculus • Arbor vitae • Cerebellar tonsil • Inferior medullary velum Molecular layer (Stellate cell, Basket cell, Parallel fiber) • Purkinje cell layer (Purkinje cell) • Granule cell layer (Golgi cell) • Mossy fibers • Climbing fiber Deep cerebellar nuclei (Dentate, Emboliform, Globose, Fastigial)
Fourth ventricle	apertures (Median, Lateral) • Rhomboid fossa (Vagal trigone, Hypoglossal trigone, Obex, Sulcus limitans, Facial colliculus, Medial eminence) • Lateral recess

v • d • e Brain: mesencephalon (midbrain)
Tectum (Dorsal)	Corpora quadrigemina: Inferior colliculi (Brachium of inferior colliculus), Superior colliculi (Brachium of superior colliculus) Subcommissural organ • Pretectum
Peduncle (Ventral)	Peduncle tegmentum Periaqueductal gray (Cerebral aqueduct, Dorsal raphe nucleus) Ventral tegmentum • Pedunculopontine nucleus • Red nucleus (Rubrospinal tract, Rubro-olivary tract)  • MLF (riMLF)  • lemnisci (Medial, Lateral) cranial nuclei: GSA (V: Mesencephalic) - GSE (III: Oculomotor, IV: Trochlear) - GVE (III: Edinger-Westphal) Interstitial cell of Cajal Superior cerebellar peduncles (Decussation of superior cerebellar peduncle) Peduncle base Substantia nigra (Pars compacta, Pars reticulata) Cerebral crus: Corticospinal tract - Corticobulbar tract - Corticopontine tract/Frontopontine fibers/Temporopontine fibers Interpeduncular fossa

v • d • e Nervous system, receptors: somatosensory system
Medial lemniscus	Touch/mechanoreceptors: Pacinian corpuscles - vibration • Meissner's corpuscles - light touch • Merkel's discs - pressure • Ruffini endings • Free nerve endings - pain • Hair cells • Baroreceptor Proprioception: Golgi organ - tension/length • Muscle spindle - velocity of change (Intrafusal muscle fiber • Nuclear chain fiber • Nuclear bag fiber)
Spinothalamic tract	Pain: Nociception and Nociceptors Temperature: Thermoreceptors

Acknowledgement and Attribution Regarding Sources of Content

Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .