The third piece is a motor, or efferent neuron. The motor neuron will take the information received from he interferon and send it on to its effectors (muscles or glands), which will activate a response. The patellar reflex is classified as a somatic reflex because it involves the stimulation of skeletal muscle, specifically stimulation of the Quadriceps femoral. It is also an example of a misogynistic reflex arc, which is simply a neural pathway controlling a somatic reflex. In a misogynistic reflex arc, there is only one motor neuron and one sensory neuron, which form a single chemical synapse.
This means when the patellar tendon is tapped with a reflex hammer, there needs to only be a very brief diminution to the muscle spindles. These muscle spindles provide the feedback that the brain needs to regulate tension in skeletal muscles. In other words, there will be very little synaptic delay when tapped, resulting in an almost immediate knee-jerk response. (2) If there is an absence or strong decrease in the knee-jerk reflex when tested it is known as Westphalia Sign, which is usually due to lesions of the lower motor neurons.
If the testing results in multiple movements after the tap of the hammer then it is most likely cerebella disease, which is often due to lesions to the upper motor erroneous. (2) This experiment was designed to test whether or not there are also mental and physical characteristics that would cause a change in the strength of the knee-jerk reflex. Three influences (muscle fatigue, simultaneous muscle activity in another part of the body, and mental distraction) were tested to see what possible factors, if any, could cause a less or more vigorous response when compared to the original, or baseline, reflex.
Based on prior research, it was predicted that the strength Of the patellar reflex will be equal to that of the baseline strength when combined tit simultaneous muscle activity or mental distraction, and less vigorous when combined with muscle fatigue Methods This experiment was designed to test the effects of mental distraction, muscle fatigue, and simultaneous muscle activity occurring in another part of the body against a baseline patellar reflex strength.
The baseline was determined by having a subject sit on top of a high lab bench with legs freely hanging not touching the ground. A Taylor Reflex Hammer was used by a fellow student (the “scientist”) to sharply tap the patellar tendon, just between the patella and the tibiae tuberose’s. Mental distraction was the first characteristic tested. The subject was given a list of fifteen A-digit numbers and was asked to mentally add up one of the three columns of numbers. While the subject added the numbers, the patellar tendon was again sharply tapped.
The second factor that was tested against the baseline was the effect of muscular activity occurring simultaneously in another area of the body. To achieve this, the subject was asked to grab a tight hold on the edge of the lab bench on either side of the legs with both hands and use all strength to pull upwards on the bench. At the same time the subject’s patellar tendon was sharply tapped. The final element that was tested against the baseline reflex was the influence of fatigue on the strength of the reflex response.
This was achieved by having the subject run up and down three levels of stairs three times in the Frost building stairwell of Holyoke Community College. The subject immediately came back to the original sitting position on the edge of the lab bench with legs dangling freely, and the patellar tendon was tapped once more. One subject was used, and was seated in the same position for each of he three tests performed. Because the patellar reflex is immediate, a video was taken during each tap with the hammer to visually compare the strength differences for each influence that was put into effect.
This provided a steady, unwavering result with the option of repeated viewing for the conclusion of the experiment. After all three stages of the experiment were completed, the videos were reviewed for comparison between the baseline reflex and the three changing factors, along with any discrepancies and problematic areas that may have altered the results. The strength of the reflex was recorded as either equal to, more vigorous than, or less vigorous than the baseline reflex and the results were put into a simple chart.
Results When testing the effects of muscle fatigue, mental distraction, and simultaneous muscular activity against the baseline strength of the patellar reflex, muscle fatigue was less vigorous, while simultaneous muscle stimulation and mental distraction were more vigorous than the strength of the baseline (fig. 1). When testing the first variable of mental distraction the subject was asked to mentally add a series a numbers in her head, without the use of paper and pencil. The purpose was to see if there was a noticeable difference when not paying attention to a reflex.
Therefore the subject was not warned before the reflex strength was tested, in order to produce the strongest response possible. The subjects’ patellar tendon was sharply tapped, and the strength was slightly more vigorous than that of the baseline. The result was videotaped in order to view the tapping after the experiment was completed. When testing the second variable of simultaneous muscle stimulation in another part of the body, the results were the same; slightly more vigorous than the baseline strength.
It was requested that both hands be placed one either side of the subjects legs on the lab bench and grasp the edge hard. The subject was then asked to pull up as hard as possible and the patellar tendon was sharply tapped. The results were again recorded by video. When testing the third variable of muscle fatigue the subject was asked to run up and down three levels of stairs in a Holyoke Community College building immediately before having the patellar reflex tested for the final time. The muscle fatigue variable was left until last so that it would not affect the results of the two other variables being tested.
The strength of the patellar reflex after imposing muscle fatigue compared with the baseline strength was less vigorous. Figure 1 . Comparison between strength of baseline patellar reflex and three various distractions Discussion The purpose of this experiment was to observe the effects that mental distraction, muscle fatigue, and simultaneous muscle stimulation in another body area has on the patellar reflex. It was hypothesized that muscle fatigue would cause a less vigorous strength in the patellar reflex, and that there would be no significant change when compared with mental distraction or simultaneous muscle stimulation.
The results of the experiment did not support the hypothesis for mental distraction or the effect of simultaneous muscle stimulation in another area of the body, which had a more vigorous response. The results did support the hypothesis that muscle fatigue would have a less vigorous response. There were several problems with the experiment that should be changed if replicated. There was only one test subject used, therefore there was nothing else to compare to the reflex strength of that one person. A small subject group often leads to inaccurate results. The same person performed the patellar reflex test; however it was to a professional.
Perhaps the area being tapped was slightly off one way or the other from the patellar tendon. If the patellar tendon was not tapped exactly, the results would not be accurate and a less vigorous response could be the outcome. The patellar tendon was difficult to find because the subject wore long pants, which made it difficult for the scientist to know exactly what to look for when tapping. Because the patellar tendon reflex is only at the spinal cord level, the brain is not involved. Therefore mental distraction should not have had any change on the strength of the reflex, but this experiment produced a more vigorous reflex.
Perhaps the subject was not fully concentrating on mentally adding the numbers, but rather paying more attention to the reflex. The anticipation of the reflex could cause a more vigorous or less vigorous outcome. Other issues included the environment and the inconsistency of the scientist performing the tests. Being able to look back at the videos taken shows several different attempts each time to tap precisely the correct spot on the patellar tendon. The results would have been more consistent if there had been a machine available that would tap he exact same spot each time the test was performed.
Since videos had been taken, the differences viewed in the reflex strength did not rely solely on memory. However, there was no accurate way of measuring the change other than estimating it. Therefore, unless the changes had been extremely less or more vigorous than baseline, it is unlikely that the recorded results could be very accurate. The environment was also not a private area. This very likely caused many other simultaneous distractions that were not meant to be a part of the experiment, which could have caused skewed results.
Conclusion The current study, although unsupported of the original hypothesis presented, does demonstrate that there are other mental and physical factors besides the simple stretching of the quadriceps femoral muscle, that contribute to the strength of the patellar reflex. The changes were not vastly different in any of the three tests. However, it is supported that there are other factors that will change the results of a patellar reflex test. Further experimentation needs to be completed with the prior changes mentioned above in order to obtain more accurate and true results.
