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The first-order neurons are sensory neurons located in the dorsal root ganglia, that send their afferent fibers through the two dorsal columns. [3] The first-order axons make contact with second-order neurons of the dorsal column nuclei (the gracile nucleus and the cuneate nucleus) in the lower medulla. The second-order neurons send their axons ...
The first-order neurons from the trigeminal ganglion enter the pons and synapse in the principal (chief sensory) nucleus or spinal trigeminal nucleus.Axons of the second-order neurons cross the midline and terminate in the ventral posteromedial nucleus of the contralateral thalamus (as opposed to the ventral posterolateral nucleus, as in the dorsal column medial lemniscus (DCML) system).
The ventral trigeminal tract - consists of second-order axons from the spinal trigeminal nucleus. These fibers cross the midline and ascend to the contralateral thalamus. The dorsal trigeminal tract - consists of second-order axons from the principal sensory nucleus of trigeminal nerve. These fibers do not cross the midline, and ascend to the ...
The dorsal trigeminal tract (also dorsal trigeminothalamic tract, or posterior trigeminothalamic tract) are uncrossed second-order sensory fibers conveying fine (discriminative) touch and pressure information from the dorsomedial division of principal sensory nucleus of trigeminal nerve to the ipsilateral ventral posteromedial nucleus of thalamus.
A somatosensory pathway will typically have three neurons: [18] first-order, second-order, and third-order. [19] The first-order neuron is a type of pseudounipolar neuron and always has its cell body in the dorsal root ganglion of the spinal nerve with a peripheral axon innervating touch mechanoreceptors and a central axon synapsing on the ...
All of these neurons are sensory (first order, or primary) and have their cell bodies in the dorsal root ganglia. They pass through Rexed laminae layers I-VI of the posterior grey column (dorsal horn) to form synapses with second order or secondary neurons in layer VII just beneath the dorsal horn.
The axons end by synapsing on third-order neurons in the inferior olivary nuclei in the medulla oblongata. The axons of the third-order neurons cross the midline and enter the cerebellum through the inferior cerebellar peduncle. [2] The spino-olivary tract conveys information to the cerebellum from cutaneous and proprioceptive organs.
The VPM receives second-order taste special visceral afferents from the solitary nucleus. [4] These synapse in the medial-most portion of the VPM, [5] which is sometimes referred to as the accessory arcuate nucleus. [6] Third-order neurons in turn project to the gustatory cortex.