![]() The general senses of somatosensation for the face travel through the trigeminal system. ![]() Other cranial nerves contain both sensory and motor axons, including the trigeminal, facial, glossopharyngeal, and vagus nerves (however, the vagus nerve is not associated with the somatic nervous system). Some cranial nerves contain only sensory axons, such as the olfactory, optic, and vestibulocochlear nerves. Whereas spinal information is contralateral, cranial nerve systems are mostly ipsilateral, meaning that a cranial nerve on the right side of the head is connected to the right side of the brain. For sensations below the neck, the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain. Cranial NervesĬranial nerves convey specific sensory information from the head and neck directly to the brain. ![]() Typically, spinal nerve systems that connect to the brain are contralateral, in that the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain. This will help to underscore the relationships between the different components. For the sake of convenience, we will use the terms ventral and dorsal in reference to structures within the spinal cord that are part of these pathways. A branch may also turn into the posterior (dorsal) column of the white matter to connect with the brain. Other branches will travel a short distance up or down the spine to interact with neurons at other levels of the spinal cord. Some of the branches will synapse with local neurons in the dorsal root ganglion, posterior (dorsal) horn, or even the anterior (ventral) horn, at the level of the spinal cord where they enter. The dorsal root contains only the axons of sensory neurons, whereas the ventral roots contain only the axons of the motor neurons. As the spinal nerve nears the spinal cord, it splits into dorsal and ventral roots. Generally, spinal nerves contain afferent axons from sensory receptors in the periphery, such as from the skin, mixed with efferent axons travelling to the muscles or other effector organs.
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