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.

Contents 1 Path 2 Location of the medial lemniscus through the brainstem 3 See also 4 Additional images 5 External links

[edit] 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.

[edit] 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.

[edit] See also

• Posterior column-medial lemniscus pathway

[edit] 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.

[edit] 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	Corpora quadrigemina: Inferior colliculi (Brachium of inferior colliculus), Superior colliculi (Brachium of superior colliculus) Subcommissural organ • Pretectum
Peduncle tegmentum	Periaqueductal gray (Cerebral aqueduct, Dorsal raphe nucleus) Ventral tegmentum • Pedunculopontine nucleus • Red nucleus • MLF (riMLF)  • lemnisci (Medial, Lateral) cranial nuclei (III: Oculomotor nucleus, III: Edinger-Westphal nucleus, IV: Trochlear nucleus, V: Mesencephalic)
Peduncle base	Substantia nigra • Cerebral crus (Corticospinal tract, Corticobulbar tract, Corticopontine tract/Frontopontine fibers/Temporopontine fibers)

v • d • e Nervous system, receptors: somatosensory system
Medial lemniscus	Touch/mechanoreceptors: Pacinian corpuscles • Meissner's corpuscles • Merkel's discs • Ruffini endings • Free nerve endings • Hair cells • Baroreceptor Proprioception: Golgi organ • Muscle spindle (Intrafusal muscle fiber • Nuclear chain fiber • Nuclear bag fiber)
Spinothalamic tract	Pain: Nociceptors Temperature: Thermoreceptors