With regards to investigating skin sensitivity, the two end points of a compass have been utilised in activating the neurons found under the skin. The smaller the distance between the two stimuli produced, the smaller and more sensitive the neuron populations had to be in order to identify both ends touching the skin. For the aforementioned reason, measurements consist of the participant's reports of how many stimuli they felt when the compass would touch their skin at different parts of their arm and distance variant between the two ends of the compass.
- There were times when the three participants on which the experiment was applied, that did not agree on whether they felt one or two stimuli on their skin. This is largely due to the unique perception and sensitivity one has.
- After a while, the participants noted they still 'felt' the two points of the compass on their skin though little pressure was applied to them. This effect could be a result of overstimulation of neurons close to one another.
- Measurements, at times, had to be repeated for errors such as wrong amount of pressure or misplacement of the compass on the skin (one side would often touch skin first than the other). The above was indicated by the participants and what they felt.
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Organising the above measurements in graphs, a better understanding of the topic can be achieved. Furthermore, an enhanced comparison of data may occur as well.
- The closer the area of nerve stimulation is to the tips of the fingers, the more sensitive the skin is to the touch of the stimuli.
- At 4 mm none of the studied areas was able to recognise the double stimuli on the skin while at 40 mm all areas could.
- The most sensitive area overall is the pad of the index finger while the least is the forearm.
The graphs seen aloft demonstrate that skin closer to the tip of the fingers is more densely packed with neuron populations. Thus, even at very small stretching of the compass, the two stimuli are conceived, compared to the skin on the upper part of the arm where neurons are not that densely populated hence, the two stimuli cannot be understood and are 'read' as one. In general terms, there is a decline of sensitivity the further up we move to the arm. In addition to this, one can also pinpoint the fact that surfaces found on the outer part of the body as is the dorsal site of the index finger or the forearm, tend to be less sensitive and thus have bigger neurons less densely populated.
Conclusion And Evaluation
To humans, senses are an indispensable part of reality. Touch is the sense with the biggest surface area and one of the most pivotal ones to survival. For the information to reach the central nervous system (CNS) consisting of the spinal cord and brain, the stimulus in the form of an electric impulse, has to move through the neurons and their elongated fibrous constructions named axons. The surface under the skin is occupied by small, packed populations of sensory neurons from which the signal is passed to the relay neurons to finally reach the CNS. The sensory neurons, in reality, act as 'translators' of an external stimulus to an electric impulse which will be finally analysed by the CNS for action to be taken. In this experiment, we identified that the closer the stimulus was to the tip of the fingers, the more sensitive the individual was to it, for the aim was to study the skin sensitivity and the minimal distance needed for a certain area to perceive the stimuli as two distinct points.
The results of this study are in main agreement with the existing evidence on the topic, since they do agree to the fact that the skin closer to the fingers and on the inner part of the body, like the pad of index finger was, is more sensitive. That is evident through the results where the minimum stretching of the compass at 8mm is perceived as two stimuli at the pad of the index finger. Less dense neuron populations yet neurons with larger surfaces, are denoted further up the arm where the stimuli were understood as two distinct points only after they had 25mm distance between one another. In the first case, two populations of neurons were activated at a smaller opening of the compass because two neuron populations were activated at the same time. For this to occur in the second case, the spread had to be bigger due to the fewer and larger, as of their surface, neuron populations that make the skin of the upper arm less sensitive.
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Despite the measures taken to prevent potential error factors, like the verifying of the results between three participants, it is still quite possible that error has arose.
- In order to measure the distance between the two end points of the compass, a ruler was used and hence, an error of 0.5mm is possible.
- Due to the fact that the whole process was conducted by the experimenter, human error is very likely to have occurred with regards to the pressure and positioning of the compass on the participants skin.
- The two stimuli provided, them being the end points of a compass had different surface areas, with the one being sharper than the other. This could make it easier to the participant to tell the difference for the two stimuli varied.
- Although the participants were blind-folded, they were biased in their reporting the stimuli since they all were students to the biology class, therefore having an idea of how the experiment would turn out to be.
Ways to improve the methodology of the experiment
- A more precise ruler could have been utilised so as to minimise the error tag even further.
- Some other device could have been used so as for the two stimuli to be identical as discussed above
This procedure could be employed in similar experiments in the future so as to investigate the difference in skin sensitivity between males and females or between people who have had a serious accident on a part of their bodies and people who have not, so as to measure neuron regeneration and/or its rate.