General somatic sensory pathways: three-neuron routes carrying pain, temperature, touch, vibration, tactile discrimination, pressure and proprioception from somatic receptors to the CNS.
Primary neuron cell bodies lie in dorsal root or cranial sensory ganglia, secondary neurons in spinal cord grey matter or brainstem sensory nuclei, tertiary neurons in the thalamus.
Classification and General Principles
Divided into three groups:
Spinothalamocerebral (spinothalamic tracts and the dorsal column-medial lemniscal pathway).
Spinocerebellar pathways.
Trigeminothalamic pathways.
All modalities are perceived at the cerebral cortex, except pain (and probably temperature), perceived at the thalamus.
Only spinothalamocerebral pathways are consciously perceived; their second-order neurons cross to the opposite side, so sensation from one side of the body reaches the contralateral cerebral hemisphere.
Interneurons may be interposed between the main sensory neurons.
The mesencephalic nucleus of the trigeminal nerve is the only first-order sensory cell body that lies within the CNS.