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Transcript
FUNCTIONAL CLASSIFICATION OF NERVE FIBER LEARNING OBJECTIVES: At the end of lecture the student should be able to Define nerve fiber Describe basic functional anatomy of a nerve fiber Classify nerve fiber NERVOUS SYSTEM Nervous system along with endocrine system control all activities of the body .primarily it is divided into Brain Spinal cord Peripheral Nervous System (PNS) Nerves that extend from the brain and spinal cord The central nervous system is composed of large number of excitable nerve cells and their process ,called neurons supported by specialized tissue called neuroglia The long process of a nerve cell are called axon or nerve fiber AXON may be very short(0.1mm) as seen in many neurons of CNS or extremely long(3.0 m)as when they extend from peripheral receptor in skin of the toe to brain Nerve fiber is the name given to an axon (or a dendrite) of a nerve cell Bundles of nerve fiber found in CNS are often referred to as nerve tract Bundles of nerve fiber found in peripheral nervous system are called peripheral nerves. CLASSIFICATION OF NERVE FIBER Depending upon structure Depending upon function Depending upon distribution Depending upon secretion of neurotransmitter Depending upon conduction velocity and diameter CLASSIFICATION OF NERVE FIBER • • • • • DEPENDING UPON STRUCTURE DEPENDING UPON FUNCTION DEPENDING UPON DISTRIBUTION DEPENDING UPON SECRETION OF NEUROTRANSMITTER DEPENDING UPON CONDUCTION VELOCITY AND DIAMETER BASIS OF CLASSIFICATION: DEPENDING UPON STRUCTURE Two types of nerve fibers are present in central and peripheral parts of nervous system Myelinated Non myelinated MYELINATED NERVE FIBER Is the one surrounded by a myelin sheath Myelin sheath is not part of neuron but is formed by a supporting cell In CNS the supporting cell is Oligodendrocyte;in peripheral nervous system it is called Schwann cell The myelin sheath is a segmented ,discontinuous layer interrupted at regular intervals by the node of Ranvier In CNS each oligodendrocyte may form and maintain myelin sheath for as many as 60 nerve fibers In the peripheral nervous system there is only one schwann cell for each segment of one nerve fiber. NON MYELINATED NERVE FIBER Example are the smaller axon of CNS, the post ganglionic axons of autonomic part of nervous system and some fine sensory axons associated with pain CLASSIFICATION ACCORDING TO FUNCTION Sensory (afferent) division Nerve fibers that carry information to the central nervous system FUNCTIONAL CLASSIFICATION OF THE PERIPHERAL NERVOUS SYSTEM Motor (efferent) division Nerve fibers that carry impulses away from the central nervous system FUNCTIONAL CLASSIFICATION OF THE PERIPHERAL NERVOUS SYSTEM Motor (efferent) division Two subdivisions Somatic nervous system = Voluntary Autonomic nervous system = Involuntary Sympathetic Parasympathetic CLASSIFICATION ACCORDING TO SECRETION OF NEUROTRANSMITTER Adrenergic nerve fiber Cholinergic nerve fiber CLASSIFICATION DEPENDING ON DIAMETER AND CONDUCTION OF IMPULSES Three major types depending on the basis of diameter and rate of conduction: Type A nerve fibers Type B nerve fibers Type C nerve fibers CLASSIFICATION OF NERVE FIBER BY SPEED OF CONDUCTION AND SIZE REFERENCES: Clinical neuroanatomy by Snell, Tortora, essential of medical physiology by Jaypees THANK YOU