These tumors are non- malignant, meaning that they do not spread or metastasize to other parts of the body. The remaining four nerves consist of significant amounts of both sensory and motor fibers.Īcoustic neuromas are benign fibrous growths that arise from the balance nerve, also called the eighth cranial nerve or vestibulocochlear nerve. Five other nerves are primarily motor in function but do have some sensory fibers for proprioception. Three of the nerves are associated with the special senses of smell, vision, hearing, and equilibrium and have only sensory fibers.
Most of the nerves have both sensory and motor components. The cranial nerves are designated both by name and by Roman numerals, according to the order in which they appear on the inferior surface of the brain. All of these nerves, except the vagus nerve, pass through foramina of the skull to innervate structures in the head, neck, and facial region. Twelve pairs of cranial nerves emerge from the inferior surface of the brain. A nerve may also have blood vessels enclosed in its connective tissue wrappings.
Within the fasciculus, each individual nerve fiber, with its myelin and neurilemma, is surrounded by connective tissue called the endoneurium. Each bundle of nerve fibers is called a fasciculus and is surrounded by a layer of connective tissue called the perineurium. Mixed nerves contain both types of fibers.Ī connective tissue sheath called the epineurium surrounds each nerve. Motor nerves have only efferent fibers, long axons of motor neurons. Sensory nerves contain only afferent fibers, long dendrites of sensory neurons. Structure of a NerveĪ nerve contains bundles of nerve fibers, either axons or dendrites, surrounded by connective tissue. The autonomic nervous system consists of nerves that connect the CNS to the visceral organs such as the heart, stomach, and intestines.
SOMATIC NERVOUS SYSTEM. SKIN
The somatic nervous system consists of nerves that go to the skin and muscles and is involved in conscious activities. The peripheral nervous system is further subdivided into the somatic nervous system and the autonomic nervous system. These nerves form the communication network between the CNS and the body parts. The peripheral nervous system consists of the nerves that branch out from the brain and spinal cord. Acknowledgements The Peripheral Nervous System
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