Recently, students in Mrs. Angelo’s Anatomy and Physiology class at Canfield High School were not only able to read about involuntary reflexes being faster than voluntary movement, but they were also able to use the scientific method to test the idea themselves. Students were able to investigate, using the LabQuest 2, how long it takes for the contraction of the quadriceps to extend the leg involuntarily and voluntarily.
The test subject, Joey Machuga, had EKG electrodes placed on specific contact areas to monitor voltage changes that triggered muscle contraction in the quadriceps muscle. A large red ‘X’ on Machuga’s leg marked the specific area that the reflex hammer with attached accelerometer, used by Tommy Warg, must contact to initiate an involuntary movement, called a knee jerk reflex.
When Warg used the reflex hammer and activated the sensors in Machuga’s knee to initiate leg extension, the reaction was very quick because the nerve impulse only needs to travel from the knee to the spinal cord and back. However, when Warg created a sound to alert Machuga to extend his leg, this voluntary action was considerably slower because the sound must travel first to the ear and then to the brain. The brain must then process the sound and send impulses back to the muscle.
The students were fascinated with the results.
“It was neat to see our hypothesis work out. We were able to measure how fast an actual impulse travels,” said Warg.
Machuga chimed in by saying, “I thought it was really cool to be the guinea pig to test the new equipment.”
While studying the nervous system, Mrs. Angelo explained that a knee jerk reflex is often used as part of a complete medical exam because slowed, absent or exaggerated reflexes may indicate a neurological or thyroid problem before other symptoms are noticed.
These non-invasive tests are like canaries in a coal mine, indicating trouble before anyone even recognizes a problem.