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Neurons
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Neurons can be classified in a number of ways. One of the earliest classifications is anatomical, according to which neurons can be unipolar, bipolar, or multipolar. Unipolar neurons have only one process emanating from the cell body. In the case of sensory neurons of the dorsal root ganglia (Figure 11.2), this single process divides at some distance from the cell body into two main branches that conduct APs from peripheral sensory receptors, past this branch point and into the spinal cord. On the other hand, most amacrine cells of the retina (Figure 7.1a) have dendrites and no axons. They neither generate nor conduct action potentials; instead they actively conduct synaptic signals through their dendrites to their target cells. Figure 7.1b illustrates a bipolar cell of the retina having an axon and a single dendrite on opposite ends of the soma. The axon of the dopamine-releasing neuron of the substantia nigra, which is a nucleus of the basal ganglia (Section 12.2.3), emerges from a dendrite up to 240 µm from the soma.
Computational Neuroscience and Compartmental Modeling
Published in Bahman Zohuri, Patrick J. McDaniel, Electrical Brain Stimulation for the Treatment of Neurological Disorders, 2019
Bahman Zohuri, Patrick J. McDaniel
Further analyses of Figure 3.7 indicate that Neurons are broadly classified as unipolar (A and B), bipolar (C), or multipolar (D). Unipolar neurons are found in invertebrate nervous systems. Pseudo-bipolar cells are typical of vertebrate sensory neurons. Their cell bodies are found in the dorsal root ganglia of the spinal cord. Many different types of sensory endings exist. Spinal motor neurons cell bodies lie in the spinal cord; their axons travel to the muscles they innervate. Very complex multipolar architectures are found in CNS interneurons. The dendritic field of the cerebellar Purkinje cells is amazingly complex.42
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
MULTIPOLAR NEURONS are the most common type in the CENTRAL NERVOUS SYSTEM: they have a CELL BODY with one AXON and multiple (typically branching) DENDRITES. A UNIPOLAR NEURON has a cell body that gives rise to a single PROCESS (therefore it is unipolar) which divides, one branch of it being the dendrite the other the axon. (These are also known as PSEUDOUNIPOLAR NEURONS, because the process eventually divides into two.) BIPOLAR NEURONS have a cell body that gives rise to one axon and one dendrite (that is, two processes, hence bipolar). Unipolar and bipolar neurons are relatively common in sensory systems: bipolar neurons for example are found in the RETINA, while unipolar neurons are found in SOMATOSENSORY systems.
Neuropsychiatric manifestations in primary Sjogren syndrome
Published in Expert Review of Clinical Immunology, 2022
Simone Appenzeller, Samuel de Oliveira Andrade, Mariana Freschi Bombini, Samara Rosa Sepresse, Fabiano Reis, Marcondes C. França
The mechanisms underlying PNS damage in the pSS are not entirely clear. However, mounting evidence indicates there is not a single pathophysiology. Pathological reports from patients with sensory neuronopathy reveal multifocal infiltration of dorsal root ganglia by T CD8(+) lymphocytes (like what is seen in glandular tissues) with direct neuronal aggression [28,67]. Here, the fenestration of capillaries at the dorsal root ganglia makes it easier for autoreactive cells to reach the target. This leads to degeneration of sensory neuron bodies and formation of Nageotte nodules. Since these are pseudo-unipolar neurons, there is subsequent degeneration of peripheral and central axonal projections coming from these neurons. There has been an active search for specific autoantigens that could trigger this inflammatory cascade. Recently, Antoine et al. identified antibodies against the transmembrane protein FGFR3 in a significant proportion of patients with immune-mediated sensory neuronopathy, including many with pSS [68]. It remains to be investigated whether this antibody has a causal role or is just a diagnostic marker for sensory neuronopathyneuronopathy.