2) Spinothalamic (Ventral & Lateral) Pathway to the Cortex
Pain & tactile sensations from limbs, trunk & neck
1. First-order neurons from sensory receptors of the limbs, trunk & neck enter the spinal cord 2. Axon terminals of first-order neurons synapse with second-order neurons located in the dorsal gray horn of the spinal cord. 3. Axons of the second-order neurons cross to the opposite side of the spinal cord and pass upward to the brain stem as the Spinothalamic Tract. 4. Axons of second-order neurons end in the Ventral Posterior Nucleus of the thalamus where they synapse with third-order neurons. 5. Axons of third-order neurons project to the primary somatosensory area on the same side of the cerebral cortex as the thalamus.
3) Trigeminothalamic Pathway to the Cortex
Conscious proprioception, tactile sensations & pain from the face, nasal cavity, oral cavity, and teeth. 1. First-order neurons from sensory receptors in the face, nasal cavity, oral cavity, and teeth extend into the pons through cranial nerve V – Trigeminal Nerve. 2. Axon terminals of some of the first-order neurons synapse with second-order neurons in the pons. 3. Axon terminals of other first-order neurons descend into the medulla to synapse with other second-order neurons. 4. Axons of second-order neurons cross to the opposite side of the pons and medulla and then ascend as the trigeminothalamic tract to the ventral posterior nucleus of the thalamus. 5. In the thalamus, axon terminals of second-order neurons synapse with third-order neurons which project their axons to the primary somatosensory area of the same side of the cerebral cortex as the thalamus.
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