The neurons in the posterior horn of the spinal cord are second-level sensory neurons, equivalent to relay stations for sensory system transmission, and are a type of cell in the gray matter of the spinal cord. The gray matter has a butterfly-like appearance in the transverse section of the spinal cord, and these cells are located at the back of the gray matter of the spinal cord, which is the posterior lateral corner of the butterfly-like wings. They are mainly involved in the tertiary neuronal conduction of the superficial senses in the body, as if they were three people in a relay race. The first level neuron, also known as the posterior root ganglion, carries various sensory fibers through the posterior lateral sulcus to the posterior horn of the spinal cord and transmits sensory impulses to the posterior horn neurons of the spinal cord, also known as the second level sensory neurons. The axons formed by the posterior horn neurons enter the contralateral or ipsilateral white matter, forming an upward fiber bundle that eventually transmits nerve impulses from the posterior root afferents to the third level neurons, the ventral posterior lateral nucleus of the thalamus in the brain, and then to the cerebral cortex.