Spinothalamic tract

Spinothalamic tract

Infobox Brain
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Caption = Spinothalamic tract is 5, in blue at right.


Caption2 = Diagram of the principal fasciculi of the spinal cord. (Anterior and posterior spinothalamic fasciculus is labeled at bottom left.)
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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.

Tracts

There are two main parts of the spinothalamic tract (STT):
* The lateral spinothalamic tract transmits pain and temperature.
* The anterior spinothalamic tract (or "ventral" spinothalamic tract) transmits light touch and pressure.

Information transmitted

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.

ub-systems

There are two sub-systems identified:
* Direct (for direct conscious appreciation of pain)
* Indirect (for affective and arousal impact of pain). Indirect projections include
** Spino-Reticulo-Thalamo-Cortical (part of the ascending reticular arousal system, aka ARAS)
** Spino-Mesencephalo-Limbic (for affective impact of pain).

Path of sensation

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.

Lesions

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.

External links

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Look at other dictionaries:

  • spinothalamic tract — n any of four tracts of nerve fibers of the spinal cord that are arranged in pairs with one member of a pair on each side and that ascend to the thalamus by way of the brain stem: a) one on each side of the anterior median fissure that carries… …   Medical dictionary

  • Lateral spinothalamic tract — Infobox Anatomy Name = PAGENAME Latin = tractus spinothalamicus lateralis GraySubject = 185 GrayPage = 762 Caption = Lateral spinothalamic tract is 5a, in blue at right center. Caption2 = Diagram of the principal fasciculi of the spinal cord.… …   Wikipedia

  • Anterior spinothalamic tract — Infobox Anatomy Name = PAGENAME Latin = tractus spinothalamicus anterior GraySubject = 185 GrayPage = 760 Caption = Anterior spinothalamic tract is 5b, in blue at right. Caption2 = Diagram of the principal fasciculi of the spinal cord. (Anterior… …   Wikipedia

  • anterior spinothalamic tract — n SPINOTHALAMIC TRACT (a) …   Medical dictionary

  • lateral spinothalamic tract — n SPINOTHALAMIC TRACT (b) …   Medical dictionary

  • ventral spinothalamic tract — n SPINOTHALAMIC TRACT (a) …   Medical dictionary

  • spinothalamic tract anterior — tractus spinothalamicus anterior …   Medical dictionary

  • spinothalamic tract lateral — tractus spinothalamicus lateralis …   Medical dictionary

  • spinothalamic tract ventral — tractus spinothalamicus anterior …   Medical dictionary

  • tract — An elongated area, e.g., path, track, way. SEE ALSO: fascicle. SYN: tractus. [L. tractus, a drawing out] alimentary t. SYN: digestive t.. anterior corticospinal t. uncrossed fibers forming a small bundle in the anterior funiculus of the …   Medical dictionary

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