Lab 6 Ulnar Nerve Stimulation and Synaptic Delay 2011

Lab 6 Ulnar Nerve Stimulation and Synaptic Delay 2011 - BIO...

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BIO 335 Human Ulnar Nerve Stimulation 1 MUSCLE COMPOUND ACTION POTENTIALS, NERVE CONDUCTION VELOCITY AND SYNAPTIC DELAY C. Evinger Goals To record the electromyogram from the Abductor Digiti Minimi ( ADM ) muscle in humans and to relate the generation of force to motor unit recruitment. To stimulate the ulnar nerve electrically at two different points and to record the muscle compound action potential from the ADM muscle. To estimate ulnar nerve conduction velocity. To estimate synaptic delay for ADM muscle activation. Background The Motor Unit The most basic element of movement that the nervous system can control is the motor unit. The motor unit is a single motoneuron and all the muscle fibers innervated by that motoneuron . When a motoneuron generates an action potential, all of the muscle fibers innervated by that motoneuron generate an action potential that causes muscle contraction that generates force. Recording Motor Unit Activity The electrical activity of a motor unit can be monitored by recording the summed action potentials generated by its muscle fibers, the electromyogram ( EMG ). The EMG can be recorded with needle electrodes inserted into a muscle or with electrodes placed on the skin above the muscle. With careful placement, a needle electrode can measure the discharge of an individual motor unit. With skin electrodes, however, it is only possible to measure the activity of multiple motor units, as a compound action potential ( CAP ). In this lab, we will monitor motor unit activity using skin electrodes. The Ulnar Nerve The ulnar nerve carries cutaneous sensory information from the fifth digit (little finger), the adjacent half of the fourth digit, and the skin of the palm and the dorsal hand proximal to those fingers (Fig. 1). Different branches of the ulnar nerve also innervate the hypothenar muscles, the abductor digiti minimi, flexor digiti minimi, and the opponens digiti minimi, and the dorsal interossei, palmar interossei, adductors pollicis, Palmaris brevis, and 3 rd and 4 th limbrical muscles. From the elbow, the path of the ulnar nerve is easy to identify. The ulnar Figure 1 from: http://pn.bmj.com/content/6/4/218/ F4.large.jpg
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