- The reflex is the photopupillary reflex, in which the pupil contracts and dilates depending on how much light is entering the eye through the pupil. Although we did not take a video of the actual pupil contraction, the pupil did shrink when the flashlight was shone on the eye. This occurred because when light enters the eye, the photopupillary reflex is triggered and the ciliary body of the iris contracts, making the pupil smaller.
Next, we tested the knee jerk reflex, which is commonly tested at the doctor's office. In this reflex, the tap below the knee sends information back to the spinal cord that tells the muscle to contract, resulting in a leg kick. I observed this when I tapped below my lab partner's knee; her knee kicked up involuntarily and immediately after I tapped her. The fact that the knee kicks up so quickly after the knee is tapped is easily explained by the concept of reflexes themselves; reflexes happen so quickly and involuntarily because the information is sent from the muscle to the spinal cord instead of the brain, and the nerve impulse to make the muscle contract is sent back to the muscle. Then, my lab partner squatted until she was tired. However, when I tapped the area below her knees even after she exercised, her knee jerk was still quite vigorous, showing that she did not exercise to the point of exhaustion.
- The knee jerk reflex is the kicking up of the knee when the area right below the knee is tapped. Again, although we did not take a video of this happening, almost all of us have experienced this at the doctor's office before. This occurred because the stimulus of the instrument used to tap the area below the knee sends a signal to the spinal cord, which relays a nerve impulse back to the muscle for the muscle to contract, making the knee jerk. Here is a picture of that process:
The knee jerk after my lab partner squatted was still vigorous because my partner had not exercised to the point of using up all of the ATP available for her muscles to contract; as a result, the muscles involved in the knee jerk reflex still contracted.
Next, we tested the blink reflex by having my lab partner hold plastic wrap in front of her face while I sporadically threw cotton balls at her face. Every time I threw the cotton balls, my lab partner blinked involuntarily. Humans have evolved this reflex throughout time in order to protect their eyes from foreign substances and other harm.
- The blink reflex is the blinking of the eye when it seems as if something will enter or harm the eye. When I threw the cotton balls toward my partner's face, she really did blink. This occurred because the body thinks that the cotton balls will hit/harm the eye, so we blink to prevent that harm from occurring.
We then tested the plantar reflex, which mainly tests neurological function. I performed this test by having my lab partner sit on a table and take off their shoe and sock, so as to leave their sole exposed. I then used a firm object and dragged it up the sole of their foot from the heel to the base of the big toe. When I did this, my partner's toes curled and plantar flexed, which is the reaction that people with normal neurological function have. However, if the person does not have normal neurological function, the toes spread apart and upward, known as Babinski's sign.
- The plantar reflex is the plantar flexion of the foot when the sole of the foot is stimulated; the toes are also supposed to curl. When I dragged a firm object across the sole of my partner's foot, my partner's foot did curl up, showing that she has normal neurological function. This reflex occurred because the stimulus of the firm object I used on the sole sent information to the spinal cord, which sent a nerve impulse back to the foot to make it flex.
Lastly, I tested reaction time by dropping a yard stick in front of my lab partner and marking the distance that it took for her to catch it, and therefore how long it took for her to catch it. For each person, we conducted three trials by dropping the yard sticks randomly three times. My average reaction time was 0.336 seconds. We also observed reaction times while texting. For this, I texted the message "Texting while driving is very dangerous because your reaction time is reduced" with one hand while looking at the phone. When my partner dropped the yard stick in my hand and I had to catch it while texting, my reaction time was significantly slower; my average time rose to 0.516 seconds.
- This last part is a bit different than the other four parts; it is testing reaction time, not reflex. For this reason, the time taken to catch the yardstick is much slower than the time for the pupil to contract or the knee to jerk; the information that the yard stick is falling has to reach all the way to the brain in order for me to catch the yardstick.
- While texting, for two of the three trials, I was so engrossed in texting that I did not even realize that my partner dropped the yardstick, so the point at which I caught the yardstick was very high up the yardstick. My trial 1 time was 0.32 seconds, my trial 2 time was 0.53 seconds, and my trial 3 time was 0.70 seconds; obviously, I did not even realize she dropped the yardstick for the last two trials. I think that my results were quite similar to the average times of everyone in the class. Here is a bar graph of the results:
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