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.

Learning More About My Nutrition

As I've been working towards my 20 time project, I've been spending most of my class time researching what foods are high in carbohydrates and fats and I've been keeping a log of all the foods I've been eating at breakfast, lunch, and dinner, each day. I've been making a chart to track the nutrients in the foods too, just as we did first semester when we did the Nutrition Analysis Activity. I learned that my regular diet is pretty bad because I go off-campus for lunch 4/5 days of the week, which explains why my nutrition analysis said I consumed a lot of carbohydrates and almost twice as many calories as I should be consuming. In addition, I've been keeping track of my mood throughout the day and I've realized that the myth about how eating unhealthy affecting one's mood might be true. I've been a lot crankier and irritable throughout the day, especially when I haven't eaten in a while. I'm hypothesizing that next month when I switch to eating healthier ever day, my carbohydrate and calorie intake will significantly reduce and my mood will increase. I think my lack of exercise this month has also played a role in my moodiness. I haven't come across any set backs as yet, but it's pretty clear that my 20 Time project has expanded what I learned in the Nutrition Analysis unit from last semester. People in the community need to be more proactive about keeping track of their diets and limiting their intake of excessively fatty foods and try to eat healthier. In addition, people need to start exercising regularly to improve their mood and burn excess fat gained from occassionally eating unhealthy foods.

Brain Dissection

In our brain dissection (depicted in the images below), we first located external structures on the brain. We located the cerebrum - pinned in yellow - which is associated with higher brain functions like thought and action. Then, we located the cerebellum - pinned in green - which coordinates the body's voluntary movements. We also located the brain stem - pinned in red - which controls the flow of signals between the brain and the body. Lastly, to give the brain an orientation, we labelled the anterior - pinned in white - and the posterior - pinned in black. Myelin, an important part of neurons are not visible to the naked eye so we could not see them in this dissection; however, it is important to note that their function is to insulate the axon of neurons and increase the speed at which impulses move along the axon. Below is an image from the dissection with the colored pins in it and a drawing of what it looked like to me. 

Once we cut through the corpus callosum - pinned in red - we could see the two hemispheres of the brain side by side, which made it easier to locate the internal structures of the brain. The corpus callosum is essentially a dense connection of nerves that passes information between the two hemispheres of the brain. Now it was possible to locate the thalamus - pinned in black - which functions as a router that integrates the information that sensory neurons take in. We could clearly see the optic nerve - the lower white pin - which hung off the brain a little bit and takes the input we take in from the eyes to the brain so it can be converted to vision. The medulla oblongata - pinned in green - was also clear here, and it's important to the brain as it regulates respiration and blood circulation. We located the pons - pinned in blue - as it controls our breathing and the communication of different parts of the brain with each other. The midbrain - pinned in yellow - controls our vision, motor skills and hearing, and is in charge of temperature regulation. Lastly, we found the hypothalamus - the upper white pin - which maintains the body's homeostasis and circadian rhythm. In the images below, you can see one hemisphere of the brain with the pins in it, my drawing of that hemisphere, and then what the two hemispheres of the brain look like side by side.

Lastly, we made a cross sectional cut in the cerebrum so that we could see what white matter and gray matter look like in the brain. Below are two pictures: one showing the cross section from the brain we dissected, and the second showing my drawing of the cross section. The white matter here appears whitish and the gray matter appears pinkish. 

For more information on specific parts of the brain and where they are located in the brain, please see my previous post about our Clay Brain Activity. We used the Clay Brain model we made in this activity to help us find the parts of the brain during this dissection and it proved to be an excellent resource!

Sheep Eye Dissection

Once light enters the eye through the pupil, the light passes through the lens. The lens changes shape to bend rays and correct angles to focuses the light on the retina. Then, the light lands on the retina, which is located at the back of the eye and is covered in photoreceptors. The photoreceptors sense the different wavelengths of light that are present and convert them into electrical signals. The optic nerve detects these signals and sends them to the brain.

In the dissection we did (depicted in the picture below), we were able to locate all of the structures depicted in the diagram above very clearly in order to understand the path that light takes as it moves through the eye and to the brain.

A Woman Perpetually Falling

Cheryl is a woman who lost her sense of balance after she was prescribed too much gentamicin to treat an infection. Due to the overdose, her inner ear structures, including the vestibular apparatus, have been thoroughly damaged. The vestibular apparatus - a structure in the ear - is the organ tasked with helping a person sense space and orientation, and so, could no longer stand without falling. A neurologist by the name of Bach-y-Rita developed a helmet that could bypass the damages vestibular apparatus and send signals directly to the part of the brain that processes balance via the tongue. The longer Cheryl wore the helmet, the longer the effect lasted and Cheryl could stay balanced without the help of the device. Long term use also eventually makes permanent adjustments to the brain so that the residual effect last longer every time. This amazing ability of the brain to take over and redelegate  the jobs of damaged brain parts proves the plasticity of the brain.

"[Cheryl] suffers from mental fatigue, as well, from being on constant high alert. It takes a lot of brain power to maintain an upright position--brain power that is taken away from such mental functions as memory and the ability to calculate and reason" (5) All of our senses are interconnected - though Cheryl has lost her sense of balance, everything else in her life is affected too. She has trouble remembering, calculating, and reasoning, all abilities that were also compromised by the damage to her vestibular apparatus. Individual sense like  balance are not isolated in regions of the brain, so when one region is affect, other cognitive abilities are also impaired.

"Her residual effect progressed to multiple hours, to days, and then to four months. Now she does not use the device at all and longer considers herself a Wobbler" (10). This truly demonstrates the elasticity of the brain. The effects of using this device lasted even when Cheryl wasn't wearing the device because the brain was able to redelegate the cognitive abilities that were impaired to other parts of the brain.

"...my father had had a huge lesion from his stroke and that it had never healed, even though he recovered all those functions" (23). This was really interesting to read, because when my grandmother had a stoke, the part of the brain that died due to the stroke, never recovered. However, her speech, ability to use her left arm, and ability to walk all came back. Even though the damaged part of the brain didn't recover, other parts of the brain adapted and adopted the functions that the brian could no longer carry out. As a result, over a couple years of physical therapy and retraining of the brain, she regained her ability to speak, use her arm, and move.

Clay Brain

To further help us understand and visualize the brain, we made two models of the human brain out of clay. One model was of the left hemisphere along the sagittal plane, while the other one was of the right cerebral hemisphere. We googled images of the brain from various angles to ensure we knew exactly where the different parts were and then used different colors of Play-Doh to make each part. We then pieced the Play-Doh together to model the brain on a piece of card board.

Can Eating Healthier For Just One Month Really Make A Difference?

For those of you who don't know, 20 Time is an open-ended project, in which the teacher dedicates 20% of class time for students to work on this project. There are little to no restrictions as to what the topic can be, so it is a great opportunity for students to explore interests they've had outside of class but have never had the chance to pursue. For my 20 Time project, I want to analyze how changing my lifestyle for just one month can change my BMI, body fat percentage, heart rate, reading on an EKG, and/or weight. According to the CDC approximately 29.1 Americans - or roughly 9.3% of Americans - had diabetes in 2012, and the percentage has been rising every year. Because my family has a long history of diabetes and, as a teenager, I have a pretty unhealthy and carb-heavy diet, I have been told that I am almost pre-diabetic. My doctor has also warned me to start being careful with what I eat because skinny people can also be diabetic. So, it's about time I start eating a little bit healthier (like getting a salad for lunch instead of pasta and eating a granola bar instead of sugary cereal) and running regularly. One of my mom’s friends is a bariatric doctor - a doctor who specializes in the causes, preventions, and treatments of obesity - said she would be able to help me with finding a diet and doing the health tests. My plan is to have one control month where I continue eating how I’ve been eating and keep track of it like we did in the nutrition analysis last semester, and then do some tests at my mom’s friend’s bariatric clinic. In addition, I will record some things about my mood and concentration throughout the day. Then, the next month I will switch to healthier options for food that she suggests and run a mile each day after school. I will track my food consumption and runs, and then conduct the same health tests after this month. I will also record thoughts about my mood and concentration. Then, I will compare the tests to see how changing my diet and exercise habits for just one month will - or will not - help me be healthier and keep me from getting diabetes if the habits are continued in the long term. I’m hypothesizing that this project will show that exercise and healthier food can significantly reduce one’s chances of getting diabetes and just generally improve one’s health and mood. In todays world, according to the National Institute of Health, 35.7% of Americans are obese and about 74% of American men are obese. I think many people (and high school students especially) will be able to relate to my video and - if my hypothesis is supported - gain some insight into how they too can change their lifestyles just a little bit to help them live healthier lives.