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The soma of a neuron (i.e., the main part of the neuron in which the dendrites branch off of) contains many organelles, including granules called Nissl granules, which are composed largely of rough endoplasmic reticulum and free polyribosomes. [5] The cell nucleus is a key feature of the soma.
The medulla and pons also contain numerous small nuclei with a wide variety of sensory, motor, and regulatory functions. In the peripheral nervous system (PNS), a cluster of cell bodies of neurons (homologous to a CNS nucleus) is called a ganglion. The fascicles of nerve fibers in the PNS (homologous to CNS tracts) are called nerves.
Nissl bodies show changes under various physiological conditions and in pathological conditions such as axonotmesis, during which they may dissolve and largely disappear (chromatolysis). If the neuron is successful in repairing the damage, the Nissl bodies gradually reappear and return to their characteristic distribution within the cell. [5]
The cell bodies of unipolar neurons are always found in ganglia. Sensory reception is a peripheral function, so the cell body is in the periphery, though closer to the CNS in a ganglion. The axon projects from the dendrite endings, past the cell body in a ganglion, and into the central nervous system. Bipolar: 1 axon and 1 dendrite.
Grey matter is distinguished from white matter in that it contains numerous cell bodies and relatively few myelinated axons, while white matter contains relatively few cell bodies and is composed chiefly of long-range myelinated axons. [1] The colour difference arises mainly from the whiteness of myelin. In living tissue, grey matter actually ...
Cranial nerve ganglia contain the cell bodies of cranial nerve neurons. Autonomic ganglia contain the cell bodies of autonomic nerves. In the autonomic nervous system, fibers from the central nervous system to the ganglia are known as preganglionic fibers , while those from the ganglia to the effector organ are called postganglionic fibers .
They possess a large cell body , with cell projections called dendrites and an axon. Dendrites are thin, branching projections that receive electrochemical signaling (neurotransmitters) to create a change in voltage in the cell. Axons are long projections that carry the action potential away from the cell body toward the next neuron.
While their cell bodies are found in the central nervous system (CNS), α motor neurons are also considered part of the somatic nervous system—a branch of the peripheral nervous system (PNS)—because their axons extend into the periphery to innervate skeletal muscles. An alpha motor neuron and the muscle fibers it innervates comprise a motor ...