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How are sensory nerve fibers different from motor nerve fibers?
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nervous system
In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.
Sensory and motor nerve fibers are distinguished primarily by the direction in which they conduct impulses and their specific functional roles within the nervous system.
- Sensory (Afferent) Fibers: These fibers carry information from the body’s external and internal environments toward the central nervous system (brain and spinal cord). They originate from sensory receptors located in tissues such as the skin, muscles, joints, and internal organs. Anatomically, their cell bodies are typically located in ganglia outside the central nervous system, such as the dorsal-root ganglia of spinal nerves.1234
- Motor (Efferent) Fibers: These fibers conduct impulses away from the central nervous system to peripheral structures, including skeletal muscle, smooth muscle, cardiac muscle, and glands. Their cell bodies are generally located within the central nervous system or in autonomic motor ganglia.314
While individual fibers are specialized, many nerves—such as spinal nerves—are considered "mixed" because they contain both sensory and motor components, allowing them to facilitate two-way communication between the body and the central nervous system.32