The anterior and lateral spinothalamic tracts are ascending sensory pathways. They begin in the periphery, travel to the spinal cord and enter 1-2 levels up at the dorsal horn (substantia gelatinosa). From here they decussate at the anterior white commisure. At this point they travel up the spinal cord, synapsing at the contralateral thalamus from where they originally began in the periphery.
The lateral spinothalamic tract carries the sensory modalities of temperature and pain. It is part of the anterolateral system, which is a bundle of sensory axons ascending through the white matter of the spinal cord, carrying sensory information to the brain.
The lateral spinothalamic tract carries temperature sensory information to the thalamus of the brain. It is composed primarily of fast-conducting, sparsely-myelinated Aδ axons and slow-conducting, unmyelinated C axons.
Pain is also transmitted via the lateral spinothalamic tract, by carrying sensory information to the thalamus of the brain. It is composed primarily of fast-conducting, sparsely-myelinated Aδ axons and slow-conducting, unmyelinated C axons.
The anterior spinothalamic tract contains fibers which convey crude touch and pressure information to the thalamus. It is part of the anterolateral system, which is an ascending sensory system.
The anterior spinothalamic tract senses crude touch. This is due to C fibers, which are actually slow pain fibers that are considered polymodal because they can react to various stimuli.
Pressure is sensed through the anterior spinothalamic tract because it contains C fibers, which are slow pain fibers, which are considered polymodal due to their response to mechanical stimuli.
The spinothalamic tract is unique because it ascends up the spinal cord contralaterally to where stimulation occurs. 1st order peripheral nerves come from the site of stimulation and terminate at the dorsal horn. From here, a second order neuron decussates through the anterior white commissure, and ascends to the thalamus on the contralateral side of the original site of nerve entry.
Lesion or injury to the spinothalamic tract gives unique manifestations. Injury to one side of the spinal cord (such as hemisection) yields contralateral anesthesia. This occurs because a nerve inserts into a side of the spinal cord, but decussates at the anterior white commisure before ascending contralaterally. Example: injury to the right spinothalamic tract at T10 would lead to left-sided anesthesia and deficits in temperature, crude touch, and pressure sensations below T10.
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