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Dorsal longitudinal fasciculus

Dorsal longitudinal fasciculus
Details
Identifiers
Latinfasciculus longitudinalis posterior,
fasciculus longitudinalis dorsalis
NeuroNames599
NeuroLex IDbirnlex_986
TA98A14.1.05.305
TA25868
FMA83845
Anatomical terms of neuroanatomy
Not to be confused with Medial longitudinal fasciculus or Superior longitudinal fasciculus.

The dorsal longitudinal fasciculus (DLF) is a distinctive nerve tract in the midbrain. It extends from the hypothalamus rostrally to the spinal cord caudally, and contains both descending and ascending fibers.

Descending fibers arise in the hypothalamus to project directly or indirectly onto autonomic nuclei and lower motor neurons of the brainstem and spinal cord; the descending component is involved in controlling chewing, swallowing, salivation and gastrointestinal secretory function, and shivering.

Among the ascending fibers is a serotonin pathway arising in the raphe nuclei.

Anatomy

Ascending fibers

Fibres arising from the nuclei of the reticular formation ascend in the DLF to terminate in the hypothalamus.[1] It conveys visceral information to the brain.[citation needed]

Fibers arising from the parabrachial area pass in the DLF to convey taste and general visceral sensation from the nucleus tractus solitarius to the posterior nucleus and periventricular nuclei of the hypothalamus.[citation needed]

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 with fibres of the more substantial ventral serotonergic pathway to commonly terminate diffusely across structures of the forebrain.[2]

Descending fibers

The descending fibers of the DLF commence in the medial zone of the hypothalamus as largely unmyelinated axons having originated from the paraventricular nucleus of hypothalamus. The axons converge to form a distinct bundle in the periaqueductal gray of the midbrain. Still more caudally, the DLF passes in the medial portion of the floor of the fourth ventricle.[1]

Descending fibers of the DLF may first[1] synapse in either the periaqueductal gray or reticular formation which in turn form relay projections onto the autonomic nuclei of the brainstem, and the lower motor neurons of the brainstem and spinal cord, respectively.[3] Some fibers project directly to the dorsal nucleus of vagus nerve, and autonomic nuclei of the spinal cord (hypothalamospinal fibers).[1]

Descending projections of the DLF are functionally involved in mediating chewing, swallowing,[3][2] salivation and gastrointestinal secretory function,[2] and shivering.[3]

The salivatory nuclei receive hypothalamic afferents which perhaps pass through the DLF.[1]

References

  1. ^ a b c d e Kiernan, John A.; Rajakumar, Nagalingam (2013). Barr's The Human Nervous System: An Anatomical Viewpoint (10th ed.). Philadelphia: Wolters Kluwer Lippincott Williams & Wilkins. pp. 109, 134, 190. ISBN 978-1-4511-7327-7.
  2. ^ a b c d Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). [New York]. pp. 460, 501–502. ISBN 978-0-7020-7707-4. OCLC 1201341621.{{cite book}}: CS1 maint: location missing publisher (link)
  3. ^ a b c d e f g Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. p. 451. ISBN 978-1-118-67746-9.
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