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There are three groupings of neurons that are involved in the pathway: first-order neurons, second-order neurons, and third-order neurons. 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 ...
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 ...
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).
One pathway—dorsal column–medial lemniscus pathway—begins with sensation from the periphery being sent via afferent nerve fiber of the dorsal root ganglion (first order neuron) through the spinal cord to the dorsal column nuclei (second order neuron) in the brainstem. The second order neuron's projection decussates at the medulla through ...
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.
After entering the spinal cord the first order neurons synapse (in the nucleus proprius), and the second order neurons decussate via the anterior white commissure. These second order neurons ascend synapsing in the VPL of the thalamus. Incoming first order neurons can ascend or descend via the Lissauer tract.
The principal sensory nucleus of trigeminal nerve (or chief sensory nucleus of V, main trigeminal sensory nucleus) is a group of second-order neurons which have cell bodies in the caudal pons. It receives information about discriminative sensation and light touch of the face as well as conscious proprioception of the jaw via first order neurons ...
A dorsal root ganglion (or spinal ganglion; also known as a posterior root ganglion [1]) is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. The cell bodies of sensory neurons known as first-order neurons are located in the dorsal root ganglia. [2] The axons of dorsal root ganglion neurons are known as afferents.