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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.
The peripheral nervous system (PNS) is divided into the somatic nervous system, the autonomic nervous system, and the enteric nervous system.However, it is the somatic nervous system, responsible for body movement and the reception of external stimuli, which allows one to understand how cutaneous innervation is made possible by the action of specific sensory fibers located on the skin, as well ...
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.
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 large majority of the axon bundles called nerves are considered to belong to the PNS, even when the cell bodies of the neurons to which they belong reside within the brain or spinal cord. The PNS is divided into somatic and visceral parts. The somatic part consists of the nerves that innervate the skin, joints, and muscles.
Small nerve of the papilla, with neurolemma. Its two nerve fibers (axons) running with spiral coils around the tactile corpuscle. Apparent termination of one of these fibers. A tactile papilla seen from above so as to show its transverse section. Cortical layer. Nerve fiber. Outer layer of the tactile body, with nuclei. Clear interior substance.
The capsule consists of 20-70 concentrically-arranged connective tissue lamellae around the axon terminal at its center, forming a structure much like an onion. [8] The capsule consists of fibroblasts and fibrous connective tissue (mainly Type IV and Type II collagen network), separated by gelatinous material, more than 92% of which is water. [9]
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 ...