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Brain: Spinothalamic tracts
Medulla spinalis - tracts - English
Spinothalamic tract is 5, in blue at right.
Gray672
Diagram of the principal fasciculi of the spinal cord. (Anterior and posterior spinothalamic fasciculus is labeled at bottom left.)
Latin '
Gray's subject #185 760
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Components
Artery
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BrainInfo/UW ancil-114
MeSH [1]

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. The pathway decussates at the level of the spinal cord, rather than in the brainstem like the posterior column-medial lemniscus pathway and corticospinal tract.

The cell bodies of neurons that make up the spinothalamic tract are located principally within the dorsal horn of the spinal cord. These neurons receive input from sensory fibers that innervate the skin and internal organs.

TractsEdit

There are two main parts of the spinothalamic tract (STT):

Information transmittedEdit

The types of sensory information transmitted via the spinothalamic tract are described as affective sensation. This means that the sensation is accompanied by a compulsion to act. For instance, an itch is accompanied by a need to scratch, and a painful stimulus makes us want to withdraw from the pain.

Sub-systemsEdit

There are two sub-systems identified:

  • Direct (for direct conscious appreciation of pain)
  • Indirect (for affective and arousal impact of pain). Indirect projections include

Path of sensationEdit

The Spinothalamic Tract, like the Dorsal Column-Medial Lemniscus Tract, use three neurons to convey sensory information from the periphery to conscious level at the cerebral cortex.

Pseudounipolar neurons (those with only one long process) in the dorsal root ganglion have axons that lead from the skin into the dorsal spinal cord where they synapse with secondary neurons in the marginal nucleus. These secondary neurons are called tract cells.

The axons of the tract cells cross over (decussate) to the other side of the spinal cord via the anterior white commissure, and to the anterolateral corner of the spinal cord (hence the spinothalamic tract being part of the anterolateral system). The axons travel up the length of the spinal cord into the brainstem. Pain travels through spinothalamic tracts, and crosses over in the spinal cord at the point it enters, and then travels up contralaterally.

Traveling up the brainstem, the tract moves dorsally. The neurons ultimately synapse with third-order neurons in several nuclei of the thalamus -- including the medial dorsal, ventral posterior lateral, and ventral medial posterior nuclei. From there, signals go to the cingulate cortex, the primary somatosensory cortex, and insular cortex respectively.

LesionsEdit

Unilateral lesion usually causes contralateral anaesthesia (loss of pain) and temperature. Anaesthesia will normally begin 1-2 segments below the level of lesion, affecting all caudal body areas. This is clinically tested by using pin pricks.


See alsoEdit

External linksEdit

Spinal cord

epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater, denticulate ligaments, conus medullaris, cauda equina, filum terminale, cervical enlargement, lumbar enlargement, anterior median fissure, dorsal root, dorsal root ganglion, dorsal ramus, ventral root, ventral ramus, sympathetic trunk, gray ramus communicans, white ramus communicans

grey matter: central canal, substantia gelatinosa of Rolando, reticular formation, substantia gelatinosa centralis, interneuron, anterior horn, lateral horn, posterior horn (column of Clarke, dorsal spinocerebellar tract)

white matter: anterior funiculus: descending (anterior corticospinal tract, vestibulospinal fasciculus, tectospinal tract), ascending (anterior spinothalamic tract, anterior proper fasciculus)

lateral funiculus: descending (lateral corticospinal tract, rubrospinal tract, olivospinal tract), ascending dorsal spinocerebellar tract, ventral spinocerebellar tract, spinothalamic tract, lateral spinothalamic tract, anterior spinothalamic tract, spinotectal tract, posterolateral tract, lateral proper fasciculus, medial longitudinal fasciculus

posterior funiculus: fasciculus gracilis, fasciculus cuneatus, posterior proper fasciculus


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