Rye Neck Students Measure Muscle Activity, Reflex Time

MAMARONECK, NY — Rye Neck High School students conducted an electromyography lab to further solidify their knowledge of nervous system regulation and the mechanism of skeletal muscle contraction.

Under the guidance of physiology teacher Matt DeBellis, the students placed sensitive electrodes on a volunteer’s quadriceps muscles to measure their muscle activity and patellar reflex time, or knee-jerk reflex. They also placed a force meter on a reflex hammer and utilized electromyography technology to measure and calculate the difference in time between the stimulus of the knee being struck and the muscle contracting.

“The purpose of this lab was to measure the difference in speed between two neuronal networks, the patellar reflex and voluntary muscle control,” DeBellis said.

Applying their knowledge of anatomy, the students determined the distance traveled by the impulse. They measured the length of the volunteer’s femoral nerve to the location of reflex integration in the spinal cord and compared it to the distance up to the motor cortex for the voluntary muscle response.

“By measuring the impulse distance and the elapsed time to muscle contraction, the students calculated the velocity or speed differences of the impulses,” DeBellis said. “Additionally, the students were able to calculate the recruitment of muscle fibers as a function of the amplitude of the EMG or electromyography waves.”

Throughout their studies, the students have been examining the mechanism of skeletal muscle contraction and have been learning how neurons communicate with each other. They recently drew different neuronal networks and created a model and a video demonstrating their understanding of muscle contraction. Through the laboratory activity, the students gained insight into the pathology of some neuromuscular diseases, such as ALS, or Lou Gehrig’s disease, and myasthenia gravis.

“My hope is that students gain a deeper understanding of neuromuscular control and the electrical nature of life,” DeBellis said. “When the test subject extended their leg out and the class saw the electrical activity on the EMG increase in response, they were amazed. It’s that connection that is so valuable in the understanding of physiology.”

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