Hypothalamospinal tract

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Hypothalamospinal tract
Details
Identifiers
Latin tractus hypothalamospinalis
TA98 A14.1.05.329
TA2 6098
FMA 77482
Anatomical terminology

The hypothalamospinal tract is an unmyelinated [1] non-decussated [2] descending nerve tract that arises in the hypothalamus and projects to the brainstem and spinal cord to synapse with pre-ganglionic autonomic (both sympathetic and parasympathetic) neurons.

Contents

The direct autonomic projections of the hypothalamospinal tract represent a minority of the autonomic output of the hypothalamus; most is thought to project to various relay structures. [3]

Anatomy

Origin

The tract originates mainly from the paraventricular nucleus of hypothalamus, [4] [2] with minor contributions from the dorsomedial, ventromedial, and posterior nuclei of hypothalamus, [4] and lateral hypothalamus. [5] [ verification needed ] The neurons of the hypothalamospinal tract receive direct afferents from the ascending nociceptive sensory spinohypothalamic tract to mediate the autonomic response to painful stimuli. [3]

The tract terminates upon pre-ganglionic autonomic neurons in the brainstem, [3] and spinal segments T1-L3 (sympathetic outflow), and S2-S4 (parasympathetic outflow). [1] [3]

Course/relations

The tract descends through the periaqueductal gray, [5] through the dorsal longitudinal fasciculus, [1] and adjacent to the reticular formation. [5] In the brainstem, it descends in the lateral tegmentum of the midbrain, pons, and medulla oblongata. In the spinal cord, it descends in the dorsolateral quadrant of the lateral funiculus. [6]

Function

Fibers of the tract terminating at the spinal segment T1 synapse with second-order neurons which in turn synapse in the superior cervical ganglion with third-order neurons which provide sympathetic innervation to the eyelids, pupil, and skin of the face. [7] The hypothalamospinal tract includes fibres by which the hypothalamus projects to the ciliospinal center in the spinal cord, a part of a brain circuit regulating pupillary dilatation as part of the pupillary reflex. [3]

Some axons of the tract contain oxytocin. [1]

Clinical significance

Lesions of the hypothalamospinal tract above spinal cord level T1 cause ipsilateral Horner's syndrome, which is characterized by a triad of ptosis, miosis, and anhidrosis due to sympathetic denervation of the face. [6]

References

  1. 1 2 3 4 Kiernan, John A.; Rajakumar, Nagalingam (2013). Barr's The Human Nervous System: An Anatomical Viewpoint (10th ed.). Philadelphia: Wolters Kluwer Lippincott Williams & Wilkins. pp. 74, 278. ISBN   978-1-4511-7327-7.
  2. 1 2 Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42th ed.). New York: Elsevier. p. 409. ISBN   978-0-7020-7707-4. OCLC   1201341621.
  3. 1 2 3 4 5 Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. pp. 204, 367, 450, 452. ISBN   978-1-118-67746-9.
  4. 1 2 Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. pp. 112, 203–204. ISBN   978-1-118-67746-9.
  5. 1 2 3 Haines, Duane E. (January 2013). Fundamental Neuroscience for Basic and Clinical Applications, with STUDENT CONSULT Online Access,4: Fundamental Neuroscience for Basic and Clinical Applications. Elsevier Health Sciences. p. 423. ISBN   978-1-4377-0294-1.
  6. 1 2 James D. Fix. High-Yield Neuroanatomy 4th Edition. Wolters Kluwer, Lippincott Williams and Wilkins. pp. 63-64.
  7. ↑ Le, Tao (2023). First Aid. McGraw Hill.
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