Somatic sensory or somatosensory pathways refer to the neural pathways that carry information related to touch, pressure, pain, temperature, and proprioception from the skin, muscles, tendons, and joints to the brain. These pathways involve several stages of processing and integration of sensory information.
The somatosensory system is divided into three main pathways: the dorsal (or posterior) column-medial lemniscus, spinothalamic (or anterolateral), and spinocerebellar pathways.
The dorsal column-medial lemniscus pathway transmits information related to proprioception, fine touch, and vibration sensation. It starts with the primary sensory neurons in the spinal cord, which synapse with secondary sensory neurons in the dorsal column nuclei in the medulla oblongata. The axons of the secondary neurons then cross over to the opposite side of the brainstem and ascend through the medial lemniscus to the thalamus, where they synapse with tertiary sensory neurons. The tertiary sensory neurons then project to the primary somatosensory cortex, where the information is processed and integrated.
The spinothalamic pathway transmits information related to pain, temperature, and crude and coarse touch sensations. It starts with the primary sensory neurons, which conduct information from the periphery to the spinal cord. These neurons then synapse with secondary sensory neurons, which cross over to the opposite side of the spinal cord and ascend through the spinothalamic pathway to the thalamus, where they synapse with tertiary sensory neurons. The tertiary sensory neurons then project to the primary somatosensory cortex, where the information is processed and integrated.
The spinocerebellar pathway is a neural pathway that carries sensory information related to proprioception from the muscles and joints to the cerebellum that overall helps in motor coordination and control. Unlike other somatosensory pathways, the spinocerebellar pathway does not involve conscious perception of sensory information.
