Recording of EMG using using EMG simulator

Aim

To record and analyze EMG signal using EMG simulator.

Apparatus Required:

1. EMG simulator
2. EMG Amplifier
3. Digital storage oscilloscope
4. connecting cables

Procedure:

1. Connect the Biosignal amplifier to main supply.
2. Connect the EMG simulator to EMG amplifier
3. Switch on the Amplifier.
4. Connect the EMG amplifier out to DSO.
5. Switch ON the DSO.
6. Set Time/ Div knob ON THE mS division
7. Voltage division knob at 5Mv
8. Now vary the amplitude and frequency knob of EMG simulator
9. If any noise in signal check for proper ground.
10. Measure amplitude and frequency from the waveform.

Theory:

The muscle cells are roughly cylindrical, with diameters between 10 and 100 um but up to afew centimeters long. They may be arranged in parallel and bound by a connective tissue envelope into a homogeneous bundle. A myofiber is a multinucleated single muscle cell. It’s basically water with some dissolved ions separated from the extra-cellular space that is mostly water with some dissolved ions. It generates a potential difference across its cell membrane by having different concentrations of ions. The fibers are excitable cells. Excitation signals are received at the synapse. Then a rapid depolarization occurs and is coupled with a contraction. It’s a process during which electrochemical events occur. The action potentials are propagated along the sarcolemma, or cell membrane, toward the end of the fiber and downward from the surface into the transverse tubular system. The propagation of the action potential along a nerve or muscle fiber includes the flow of ions and gives rise to extra-cellularly recordable potential gradient. These potential gradients, moving in both time and space, constitute the electricity as recorded from active muscle fibers. Thus the small currents are generated prior to the generation of muscle force

Acquisition of EMG:

As the brain's signal for contraction increases, it both recruits more motor units and increases the "firing frequency" of those units already recruited. All muscle cells within one motor unit become active at the same time. By varying the number of motor units that are active, the body can control the force of the muscle contraction. When individual motor contract, they repetitively emit a short burst of electrical activity known as the motor unit action potential (MUAP). It is detected by electrodes on the surface of the skin in proximity of the motor. The detection is illustrated in the following figure. The function unit of a muscle is the motor. All the fibers which belong to one motor are activated at the same time. The motor unit action potential (MUAP) is the electrical response to the impulse from the axon. A MUAP looks like the following figure.

Result:

The EMG signal is recorded and analyzed the waveform.