Nerve Conduction Study

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UNIVERSITY OF SHARJAH COLLEGE OF MEDICINE MUSCLOSKELETAL UNIT PHYSIOLOGY PRACTICAL HANDOUT PREPARED BY: DR SUNDUS AL-OMAR ACADEMIC YEAR (2011-2012) Nerve Conduction Velocity Theory background The nerve impulse is a wave of depolarization immediately followed by a wave of repolarization, collectively called an action potential, occurring on the plasma membrane of a nerve fiber. Changes in ion conductance across the nerve fiber membrane are responsible for the initiation and propagation of the action potential. Experimentally, these changes can be the result of electrical current applied through electrodes. Once initiated, an action potential is usually propagated without decrement in amplitude or velocity along the plasma membrane of a nerve fiber. In the peripheral nervous system, nerve fibers of various diameters and functions (motor and sensory) are bundled together by connective tissue to form nerves. A compound action potential is the sum of all the action potentials occurring in the individual neurons of the whole nerve. The velocity of the compound action potential signal can be a measure and can indicate the state of health of the nerve. Diseases that damage the myelin, destroy neurons, or constrict the whole nerve will decrease the nerve's conduction velocity. The nerve conduction velocity is determined by recording the motor response of a muscle to the stimulation of its motor nerve at two or more points along the nerve course. The time between stimulation and response is measured and compared to the distance between the point of stimulation and point of response. Precise parameters of measurement have been developed for the ulnar nerve and the motor response is measured over the abductor digiti minimi. The ulnar nerve comes from the medial cord of the brachial plexus, and runs inferior on the medial/posterior aspect of the

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