Download FUNCTIONAL CLASSIFICATION OF NERVE FIBER LEARNING

FUNCTIONAL CLASSIFICATION OF NERVE FIBER
LEARNING OBJECTIVES:
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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
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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
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Depending upon structure
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Depending upon function
Depending upon distribution
Depending upon secretion of neurotransmitter
Depending upon conduction velocity and diameter
CLASSIFICATION OF NERVE FIBER
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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
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Two types of nerve fibers are present in central and peripheral parts of nervous
system
Myelinated
Non myelinated
MYELINATED NERVE FIBER
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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
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The myelin sheath is a segmented ,discontinuous layer interrupted at regular
intervals by the node of Ranvier
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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
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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
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Adrenergic nerve fiber
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Cholinergic nerve fiber
CLASSIFICATION DEPENDING ON DIAMETER AND CONDUCTION OF
IMPULSES
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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:
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Clinical neuroanatomy by Snell, Tortora, essential of medical physiology by
Jaypees
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