The lateral spinothalamic tract (or lateral spinothalamic fasciculus), which is a part of the Anterolateral system

Anterolateral system

In the nervous system, the anterolateral system is an ascending pathway that conveys pain, temperature , and crude touch from the periphery to the brain. It comprises three main pathways:-External links:*...

, is a bundle of sensory axons ascending through the white matter of the spinal cord, carrying sensory information to the brain. It carries pain and temperature sensory information to the thalamus

Thalamus

The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

 of the brain. It is composed primarily of slow-conducting, sparsely-myelinated Aδ axons and slow-conducting, unmyelinated C axons. These are secondary sensory neurons which have already synapsed with the primary sensory neurons of the peripheral nervous system in the dorsal horn of the spinal grey matter.

Together with the anterior, or ventral spinothalamic tract, the lateral spinothalamic tract is sometimes termed the secondary sensory fasciculus or spinal lemniscus.

Anatomy

The neurons of the lateral spinothalamic tract originate in the spinal ganglia. They project peripheral processes to the tissues in the form of free nerve endings which are sensitive to molecules indicative of cell damage. The central processes enter the spinal cord in an area posterior to the dorsal horn known as the dorsolateral fasiculus of Lissauer. Here, the processes ascend approximately two levels before synapsing on second-order neurons. These neurons are situated in the dorsal horn, specifically in the Lamina of Rexed regions I, II, and V. Region II is primarily composed of Golgi type II interneurons, are primarily for the modulation of pain, and largely project to regions I and V. Regions I and V decussate across the anterior comissure and ascend in the (now contralateral) lateral spinothalamic tract. These fibers will ascend through the medulla and through the pons and midbrain as the spinal lemniscus until synapsing in the Ventroposteriorlateral (VPL) nucleus of the thalamus. The third order neurons in the thalamus will then project through the internal capsule and corona radiata to various regions of the cortex, primarily the main somatosensory cortex SI, Brodmann's Areas 3, 1, and 2.

Function

The fibres conduct impulses of pain and temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

. Aδ fibres conduct immediate, sharp pain. C fibres conduct dull, burning pain.