The Peripheral Nervous System
The peripheral nervous arrangement consists of the nerves that branch out from the mind and spinal cord. These nerves form the communication network between the CNS and the body parts. The peripheral aflutter organization is far subdivided into the bodily skittish system and the autonomic nervous organization. The bodily aflutter system consists of nerves that go to the bark and muscles and is involved in conscious activities. The autonomic nervous system consists of nerves that connect the CNS to the visceral organs such as the heart, stomach, and intestines. It mediates unconscious mind activities .
Structure of a Nerve
A nerve contains bundles of nerve fibers, either axons or dendrites, surrounded by connective tissue. Sensory nerves contain only afferent fibers, long dendrites of sensory neurons. Motor nerves have only efferent fibers, long axons of motor neurons. Mixed nerves contain both types of fibers.
A connection tissue sheath called the epineurium surrounds each nerve. Each package of boldness fibers is called a fiber bundle and is surrounded by a layer of connective weave called the perineurium. Within the fiber bundle, each individual nerve fiber, with its myelin and neurolemma, is surrounded by conjunction tissue called the endoneurium. A nerve may besides have blood vessels enclosed in its connection tissue wrappings .
Twelve pairs of cranial nerves emerge from the inferior coat of the brain. All of these nerves, except the vagus nerve, pass through foramen of the skull to innervate structures in the head, neck, and facial region .
The cranial nerves are designated both by name and by Roman numerals, according to the ordering in which they appear on the inferior surface of the brain. Most of the nerves have both centripetal and motive components. Three of the nerves are associated with the special senses of smell, vision, hearing, and equilibrium and have merely centripetal fibers. Five early nerves are primarily motor in affair but do have some centripetal fibers for proprioception. The remaining four nerves consist of significant amounts of both sensational and motor fibers.
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acoustic neuromas are benign hempen growths that arise from the balance nerve, besides called the eighth cranial nerve or vestibulocochlear heart. These tumors are non- malignant, meaning that they do not spread or metastasize to other parts of the body. The localization of these tumors is abstruse inside the skull, adjacent to vital brain centers in the mind stem. As the tumors enlarge, they involve surrounding structures which have to do with vital functions. In the majority of cases, these tumors grow slowly over a period of years. In early cases, the growth rate is more rapid and patients develop symptoms at a fast pace. normally, the symptoms are balmy and many patients are not diagnosed until some fourth dimension after their tumor has developed. many patients besides exhibit no tumor growth over a number of years when followed by annual MRI scans .
Thirty-one pairs of spinal nerves emerge laterally from the spinal cord. Each couple of nerves corresponds to a segment of the cord and they are named accordingly. This means there are 8 cervical nerves, 12 pectoral nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal heart.
Each spinal anesthesia heart is connected to the spinal cord by a abaxial root and a adaxial root. The cell bodies of the centripetal neurons are in the abaxial ancestor ganglion, but the centrifugal nerve cell 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 anesthesia nerves have both sensational and centrifugal components, they are all desegregate nerves.
Autonomic Nervous System
The autonomic nervous organization is a intuitive efferent system, which means it sends centrifugal impulses to the intuitive organs. It functions automatically and endlessly, without conscious effort, to innervate fluent brawn, cardiac muscleman, and glands. It is concerned with heart pace, breathing rate, blood pressure, body temperature, and other intuitive activities that work together to maintain homeostasis .
The autonomic anxious system has two parts, the harmonic division and the parasympathetic nervous system division. many intuitive organs are supplied with fibers from both divisions. In this character, one induce and the other inhibits. This antagonistic functional relationship serves as a libra to help maintain homeostasis.