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Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Eyesenck, M. Simply Psychology. Coon, D.
Belmont, CA: Wadsworth; About Peripheral Nerves Currently selected. About Peripheral Nerves. Page Content. Nerves In the Peripheral Nervous System Brachial plexus radial nerve, median nerve, ulnar nerves Peroneal nerve foot drop Femoral nerve Lateral femoral cutaneous nerve Sciatic nerve Spinal accessory nerve Tibial nerve. Content Area Two. If we consider the entire nervous system as an electric grid, the central nervous system would represent the powerhouse, whereas the peripheral nervous system would represent long cables that connect the powerhouse to the outlying cities limbs, glands and organs to bring them electricity and send information back about their status.
Image credit: Alessandra Donato. Basically, signals from the brain and spinal cord are relayed to the periphery by motor nerves, to tell the body to move or to conduct resting functions like breathing, salivating and digesting , for example. The peripheral nervous system sends back the status report to the brain by relaying information via sensory nerves see above image.
As with the central nervous system, the basic cell units of the peripheral central nervous system are neurons. Each neuron has a long process, known as the axon, which transmits the electrochemical signals through which neurons communicate.
Axons of the peripheral nervous system run together in bundles called fibres , and multiple fibres form the nerve , the cable of the electric circuit.
The nerves, which also contain connective tissue and blood vessels, reach out to the muscles, glands and organs in the entire body. Nerves of the peripheral nervous system are classified based on the types of neurons they contain - sensory, motor or mixed nerves if they contain both sensory and motor neurons , as well as the direction of information flow — towards or away from the brain.
Thirty-one pairs of spinal nerves emerge laterally from the spinal cord. Each pair of nerves corresponds to a segment of the cord and they are named accordingly. This means there are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve. Each spinal nerve is connected to the spinal cord by a dorsal root and a ventral root. The cell bodies of the sensory neurons are in the dorsal root ganglion, but the motor neuron cell bodies are in the gray matter.
The two roots join to form the spinal nerve just before the nerve leaves the vertebral column. Because all spinal nerves have both sensory and motor components, they are all mixed nerves. The autonomic nervous system is a visceral efferent system , which means it sends motor impulses to the visceral organs. It functions automatically and continuously, without conscious effort, to innervate smooth muscle , cardiac muscle , and glands.
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