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In the nervous system, axons may be myelinated, or unmyelinated. This is the provision of an insulating layer, called a myelin sheath. The myelin membrane is unique in its relatively high lipid to protein ratio. [17] In the peripheral nervous system axons are myelinated by glial cells known as Schwann cells.
Nerve cell and organization. Each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. The entire nerve is wrapped in a layer of connective tissue called the epineurium.
The axon primarily carries nerve signals away from the soma and carries some types of information back to it. Many neurons have only one axon, but this axon may—and usually will—undergo extensive branching, enabling communication with many target cells. The part of the axon where it emerges from the soma is called the axon hillock.
Nervous tissue is composed of neurons, also called nerve cells, and neuroglial cells. Four types of neuroglia found in the CNS are astrocytes, microglial cells, ependymal cells, and oligodendrocytes. Two types of neuroglia found in the PNS are satellite glial cells and Schwann cells. In the central nervous system (CNS), the tissue types found ...
In the central nervous system (brain, spinal cord and optic nerves), myelination is formed by specialized glial cells called oligodendrocytes, each of which sends out processes (limb-like extensions from the cell body) to myelinate multiple nearby axons; while in the peripheral nervous system, myelin is formed by Schwann cells (neurolemmocytes ...
These cells do have sensory afferent dendrites, similar to those typically inherent in neurons. [1] They have a smooth and rounded cell body located in the ganglia of the peripheral nervous system. Just outside the spinal cord , thousands of afferent neuronal cell bodies are aggregated in a swelling in the dorsal root known as the dorsal root ...
When a nerve axon is severed, the end still attached to the cell body is labeled the proximal segment, while the other end is called the distal segment. After injury, the proximal end swells and experiences some retrograde degeneration, but once the debris is cleared, it begins to sprout axons and the presence of growth cones can be detected.
Association fibers are axons (nerve fibers) that connect cortical areas within the same cerebral hemisphere. [1]In human neuroanatomy, axons within the brain, can be categorized on the basis of their course and connections as association fibers, projection fibers, and commissural fibers. [1]