Programa
Electromyography
In this experiment, you will explore the electrical activity of skeletal muscle by recording an electromyogram (EMG) from a volunteer. You will examine the EMG of both voluntary and evoked muscle action and attempt to measure nerve conduction velocity.
Written by staff of ADInstruments.
[pic]
Background
A skeletal muscle fiber is innervated by a branch of a motor axon. Under normal circumstances, a neuronal action potential activates all of the muscles innervated by the motor neuron. This activation process involves an action potential and a contraction of the muscle fibers. During a contraction, therefore, there is synchronous activity in a number of fibers in the same muscle. The electrical signal recorded from a contracting muscle is called an electromyogram or EMG. Like the electrocardiogram (ECG), this activity can be detected by electrodes placed on the skin. A voluntary muscle contraction is produced by one or more action potentials in many fibers. The EMG activity is not a regular series of waves like the ECG, but a chaotic burst of overlapping spike-like signals.
In this experiment, you will record EMG activity during voluntary contractions of the biceps and triceps muscles of the arm. The raw EMG signal during voluntary contractions may be processed in various ways to indicate the intensity of EMG activity. In the method used here, the negative-going portions of the EMG are inverted, and then the whole signal is integrated in such a way as to smooth out individual spikes, and make the time course of changing activity much clearer. You will also record EMG signals produced by electrical stimulation of a motor nerve supplying a muscle. The abductor pollicis brevis muscle a member of the thenar muscle group on the palmar surface of the hand. The motor nerve to this muscle (the median nerve) is easy to stimulate at the wrist and elbow.
Required Equipment
A computer system
Chart software, version 5.0 or
In this experiment, you will explore the electrical activity of skeletal muscle by recording an electromyogram (EMG) from a volunteer. You will examine the EMG of both voluntary and evoked muscle action and attempt to measure nerve conduction velocity.
Written by staff of ADInstruments.
[pic]
Background
A skeletal muscle fiber is innervated by a branch of a motor axon. Under normal circumstances, a neuronal action potential activates all of the muscles innervated by the motor neuron. This activation process involves an action potential and a contraction of the muscle fibers. During a contraction, therefore, there is synchronous activity in a number of fibers in the same muscle. The electrical signal recorded from a contracting muscle is called an electromyogram or EMG. Like the electrocardiogram (ECG), this activity can be detected by electrodes placed on the skin. A voluntary muscle contraction is produced by one or more action potentials in many fibers. The EMG activity is not a regular series of waves like the ECG, but a chaotic burst of overlapping spike-like signals.
In this experiment, you will record EMG activity during voluntary contractions of the biceps and triceps muscles of the arm. The raw EMG signal during voluntary contractions may be processed in various ways to indicate the intensity of EMG activity. In the method used here, the negative-going portions of the EMG are inverted, and then the whole signal is integrated in such a way as to smooth out individual spikes, and make the time course of changing activity much clearer. You will also record EMG signals produced by electrical stimulation of a motor nerve supplying a muscle. The abductor pollicis brevis muscle a member of the thenar muscle group on the palmar surface of the hand. The motor nerve to this muscle (the median nerve) is easy to stimulate at the wrist and elbow.
Required Equipment
A computer system
Chart software, version 5.0 or