Reflex Lab

In this lab, we tested out various reactions that result from these reflexes: the photopupillary reflex, the knee jerk reflex, the blink reflex, and the plantar reflex. We did various activities in which we tested our individual response times to a certain stimulus and we conducted multiple trials for each reflex. To test our response time, we also conducted on activity that measured how fast we could catch a ruler when texting versus when not. In the lectures in class, we have learned that reflexes are defined as rapid, predictable, and involuntary responses to external stimuli. A reflex arc is a pathway that goes to nerve impulses, but doesn't go to the brain. Reflexes are natural and involuntary reactions that are innate and are a sign that the body is healthy, which is why it is the firs thing that physicians test when you walk into a doctor's office. The neurons that sense these impulses are highly specialized and transmit messages between different parts of the body.

Claim Evidence Reasoning...

Part 1: Photopupillary Reflex
Claim: When the intensity of light entering the eye suddenly increases, the eye's photopupillary reflex is triggered, and the cilliary body of the iris is stimulated to contract. Thus, the pupil decreases in size and less light is allowed to enter the eye, giving the eye time to adjust to the sudden change in the amount of light it is exposed to.

Evidence: In the activity we did, I covered both of my eyes with my hands and Divya timed it for two minutes. When the two minutes were up, I rapidly removed my hand from in front of my right eye as Divya shined a flashlight close to it. She recorded my eye's reaction to the change in light using the slow motion feature on her iPhone. We observed the recording and could clearly see the pupil rapidly shrink in size. This rapid decrease in size limited the amount of light that can enter the eye until the eye was able to adjust to the intensity of light.

Reasoning: The pupil decreased in size because the sudden change from darkness to a bright flashlight triggered the photopupillary reflex, which occurs when the intensity of the light entering the eye increases.

Part 2: Knee Jerk Reflex

Claim: The knee jerk reflex, also known as the patellar reflex, is one we are most familiar with because it is most commonly tested by physicians during check ups. This reflex extends from the sensory neuron to the spinal cord to a motor neuron and then back to the knee. It is a monosynaptic reflex because there is only one synapse in the circuit needed to complete the reflex. When Divya hit my knee at a certain spot near my knee cap, my leg quickly kicked out just slightly. 

Evidence: In the activity we did, Divya hit my knee at a spot just below the knee cap with a reflex hammer. At first, my leg did not kick out because she couldn't find the right spot to hit, but after a couple more tries, my leg kicked out slightly, indicating that the patellar reflex had been triggered. Initially, the activity didn't work because we were not hitting the right place, but as soon as Divya hit right under the knee cap, my leg kicked out.

Reasoning: The tap just below the knee causes the thigh muscle to stretch, sending the information to the spinal cord. After passing across one synapse in the ventral horn of the spinal cord, the information is sent back out to the muscle and the knee kicks out. This patellar reflex is one of the easiest and fastest to test because the response is so immediate and apparent.

Part 3: Blind Reflex

Claim: The blind reflex is when a person's eye automatically closes really fast when they sense that an object is rapidly approaching the eye. When Divya threw a cotton ball in my direction, I immediately blinked and she did the same when I threw a cotton ball at her. 

Evidence: I stood on one side of a window and Divya stood on the other. Then, she threw a cotton ball at me and I did the same to her after. Every time the cotton ball was thrown in our direction, we immediately blinked, demonstrating that the blink reflex worked for both of us.

Reasoning: People blink typically 15 times per minute, and this reflex protects the cornea from contact and injury that can be caused by foreign objects. This reflex is triggered by sensory stimuli that activate different neurons in the body, which send signals that cause the eyelids to shut fast.

Part 4: Babe, what's your sign
Claim: The plantar reflex, a commonly used neurological test, is triggered when the sole of the food is in contact with a blunt instrument. Our claim is that when the bottom of the foot is scraped with a blunt object, the toes of the feet flex and move closer together, demonstrating that this reflex is functioning properly.

Evidence: In this activity, I sat up on a table and took the shoe and sock off of one foot. Divya took the back end of a pen with a cap on it and firmly grazed the pen up the sole of my foot from the heel of the foot to the base of the big toe. We observed that as Divya moved the pen along my foot, my toes flexed and moved closer together. When we switched places and I moved the pen along the bottom of her foot, the same result was seen.

Reasoning: The feet reacted this way because the movement of the pen triggered the plantar reflex. This reflex is a response that happens as a reaction to a certain stimuli. When there is nerve damage to a person's body, he/she might show Babinski's sign, which is when the toes spread apart and upward. This typically occurs in newborn children because their nervous systems have not been myelinated yet.

Part 5: How Fast are You?

This activity was designed to measure students' response times to something in their periphery. In this activity, I held the meter stick near the end with the highest number and let the rest of it hang down. Divya held her hand at the bottom of the meter stick, ready to grab it when it fell. We recorded the level (in centimeters on the meter stick) at which she was able to  caught the ruler. We conducted three trials for each person and took the average time (using the table to convert the distance to time).

This activity measure how long it took for the visual information to travel to the brain and then turn into action in the hand. The brain sent a motor command to the muscles of the arm and hand to do this. My average reaction time for this part of the activity was 0.18 seconds.

We repeated the test again, except this time each of us was texting when the ruler was dropped. This portion of the activity was meant to simulate how a person's reaction time is impaired when they are texting while driving (Or doing anything else for that matter). The results of this activity showed that our reaction time significantly decreased.

My average reaction time without texting was 0.18 seconds but my average time when I was texting was 0.42 seconds, which shows that texting did have a huge effect on my time. I will definitely think about this activity when my phone buzzes or lights up with a text message when I'm driving. We all know and have heard that texting significantly impacts our reaction time while driving, but this activity reinforced this and made it more concrete for me how dramatic the effects are.