For example the vagus nerve has sensory axons leading to the brain as well as motor axons leading to the heart and smooth muscles of visceral organs in the thorax and abdomen. Others contain sensory and motor axons and are termed mixed nerves. optic nerve contains only sensory axons which carry signals to the brain. Fishes and amphibians have only 10 pairs. Reptiles birds and Mammals have 12 pairs of cranial nerves. Cranial nerves: In addition to paired spinal nerves peripheral nervous system of vertebrates includes paired cranial nerves.By contrast a snake, which moves by lateral undulations of its long trunk and tail has several hundred pairs of spinal nerves. For example a frog has evolved strong hind legs for swimming or jumping, a reduced trunk and no tail in the adult. Generally the number of spinal nerves is directly related to the number of segments in the trunk and tail of a vertebrate. Thus, they include diseases of the nerve. Spinal nerves: Extending from spinal cord are paired spinal nerves containing both motor and sensory fibres. Somatic nervous system diseases are diseases of the peripheral nerves that are external to the brain and spinal cord.Because the autonomic nervous system regulates involuntary or automatic functions, it is called the involuntary nervous system.Difference between cranial nerve and spinal nerve It is further subdivided into sympathetic and parasympathetic divisions. The autonomic nervous system, also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle, to smooth muscle, and to glandular epithelium. Because these nerves permit conscious control of the skeletal muscles, it is sometimes called the voluntary nervous system. The somatic nervous system, also called the somatomotor or somatic efferent nervous system, supplies motor impulses to the skeletal muscles. The efferent or motor division transmits impulses from the CNS out to the peripheral organs to cause an effect or action.įinally, the efferent or motor division is again subdivided into the somatic nervous system and the autonomic nervous system. The afferent or sensory division transmits impulses from peripheral organs to the CNS. The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent ( motor) division. Ganglia are collections, or small knots, of nerve cell bodies outside the CNS. Cranial nerves and spinal nerves extend from the CNS to peripheral organs such as muscles and glands. Nerves are bundles of nerve fibers, much like muscles are bundles of muscle fibers. The organs of the peripheral nervous system are the nerves and ganglia. Although considered to be two separate organs, the brain and spinal cord are continuous at the foramen magnum. ![]() The brain is in the cranial vault, and the spinal cord is in the vertebral canal of the vertebral column. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. ![]() ![]() The autonomic nervous system will be addressed in a. The brain and spinal cord are the organs of the central nervous system. Autonomic neurons are further subdivided into sympathetic and parasympathetic systems (see first figure). The nervous system as a whole is divided into two subdivisions: the central nervous system ( CNS) and the peripheral nervous system ( PNS). Each subdivision has structural and functional characteristics that distinguish it from the others. One of its roles is to relay information from the eyes, ears, skin and muscle to. Although each subdivision of the system is also called a "nervous system," all of these smaller systems belong to the single, highly integrated nervous system. The somatic nervous system is also a part of the peripheral nervous system. Acknowledgements Organization of the Nervous SystemĪlthough terminology seems to indicate otherwise, there is really only one nervous system in the body.
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