Owl Pellet Lab Analysis/Conclusion

In this lab, we were given an owl pellet which we dissected to find the remnants of the organism that the owl had consumed. We first took down the mass, length, and width of the pellet as 5.82 g, 3.7 cm, and 3.0 cm respectively. Then using forceps and a probe we separated the bones in the pellet from the fur, making one pile of each. Using the key on page 15 in our dissection lab handout and measurements of the bones we found, we were then tasked with deciding what animal it was. Unfortunately, we were unable to find enough bones to piece together the entire skeleton of our organism, but we found enough evidence to make a claim as to what it might be.

Claim: From the results of this lab, we concluded that the skeleton we found in our owl pellet most likely belonged to a mouse.

Evidence: The skull we found has teeth with a gap (diastema) between the incisor teeth and molar teeth. Because these teeth - when inspected under a dissecting microscope - had a rounded shape with no visible roots, we could narrow down that the skeleton belonged to either a rat or a mouse. Because the length of the skull was less than 25 mm (it was 15 mm) and the length of the lower jaw was between 9-16 mm (it was 11 mm), we concluded that the skeleton belonged to a mouse.  In addition, the hip bones we found were similar to images of mouse hip bones shown on page 16 of the lab handout.

Reasoning: Following the steps of the dichotomous key on Page 15 of the lab manual, we went from step 1 to step 2 to step 3 to step 4, ending at (b) of step 4. In this way, we were able to conclude that the skeleton we found belonged to a mouse. In addition, the bones we found in the owl pellet matched the images and scale of what mouse bones should look like, as shown on Page 16 of the lab handout. Both, the dichotomous key on Page 15 and the pictures of various rodent bones on Page 16 helped us reason out that the organism was most likely a mouse.

The skeleton of the shrew we found could be compared to that of a human.
Some similarities we noticed between the mouse and a human skeleton were:
(1) The mouse skull and human skull shared many structural similarities - the structure of the jaw/mandible was similar and the location of the eyes, mouth, and nose, were similar in both skulls.
(2) The mouse hip bones (tibia, fibia, and femur) which we pieced together very similarly matched the anatomy of the human hip bone.
(3) Both, the mouse skull and human skull have teeth with similar structures and the teeth are found in the same place in both the mouse and human skull.

Some differences we noticed between the mouse and a human skeleton were:
(1) The mouse skull has a gap (diastema) between the incisor and molar teeth, which the human skull does not have.
(2) The human skull is longer vertically, whereas the mouse skull is longer horizontally.
(3) The human eye socket is circular, whereas the mouse skull we found had more oval-shaped eye socket.

Extending the Power Hour Reading: The Brain That Changes Itself by Norman Doidge, M.D.

During the Power Hour Reading, I read an excerpt from The Brain That Changes Itself by Norman Doidge, M.D. I found this book quite fascinating, so I took it home and read the whole thing to learn more about brain plasticity. The first chapter, which we read in class, discusses how a woman named Cheryl regains the ability to balance. See more about the first chapter of this book in my previous blog post about it here. Similarly, the rest of the chapters in his novel detail different people and their stories about how their brains managed to adapt to and compensate for various brain injuries. The major claim/thesis that the author, Norman Doidge, makes throughout this book is that the brain can adapt to overcome injuries and take over the jobs of parts of the brain that die or are affected by the injury - a phenomenon known as neuroplasticity.

It’s funny how I’ve been learning so much in AP Biology about how the animals around us have been adapting for millions of years to fit the changing environment and conditions on Earth. It’s interesting to see how this same principle of evolving and changing is evident in our own brains as well. Doidge draws a direct parallel to this when he says, “the brain is a far more open system than we ever imagined, and nature has gone very far to help us perceive and take in the world around us. It has given us a brain that survives in a changing world by changing itself.” In much the same way that organisms evolve to the changing conditions on Earth, our brains change and adapt to the conditions of our body. This quote articulates the principle of neuroplasticity quite perfectly. In addition, Doidge personifies the brain a little bit to reiterate his main point when he says, “We must be learning if we are to feel fully alive, and when life, or love, becomes too predictable and it seems like there is little left to learn, we become restless - a protest, perhaps, of the plastic brain when it can no longer perform its essential task.” This is another great quote that quite beautifully illustrates this principle of elasticity. He compares our human desire to constantly learn to that of the brain. When a part of the brain dies, it stops learning. However, the brain cannot stand to be plastic and so it will retaliate and do what it needs to in order to keep learning. Thus, the brain will get restless and reorganize its neural pathways to try to regain whatever function was lost from a brain injury. A common thread throughout the anecdotes shared in these chapters is that the individuals all “have senses [that they] didn't know [they] have until [they] lose them.” This quote, although seemingly unrelated to the main point of neuroplasticity, really resonated with me. It echoed the same principle that we’ve been taught since we were children that “you never know what you’ve got until you don’t have it anymore.” This is ever more apparent with the brain injury patients that are discussed in this novel - they all take the functions of their brain for granted until something goes wrong and they are forced to reteach their brains to do something. They realize how every sensation and neural pathway is important for them to function and live normally. This just goes to show how we need to appreciate the power of our brains and take care of ourselves. But if and when something does go wrong, we owe it to ourselves to bear grueling therapy to reteach our brains the functions that were lost.  

In Chapter 5 (one of my favorite chapters), for example, Doidge discusses how a stroke patient regained the ability to move and speak. As I’ve mentioned before in previous blog posts, reading about this is always very personal and fascinating for me because my grandmother had a stroke 3 years ago and I also did research on this topic this past summer. Michael Bernstein - the patient discussed in this chapter - had a stroke to the same side of the brain that my grandmother did and the stroke initially paralyzed the entire left side of his body. This is because when a person has a stroke, the tissue on the side of the brain that doesn’t get blood permanently dies. Similarly, when my grandmother had her stroke, her speech, the mobility of her left arm, and her ability to walk properly were all affected. Slowly but surely, with physical and occupational therapy, she was able to train other parts of her brain to take over the functions that the right side of her brain was once responsible for. In doing so, she was able to regain the ability to speak without a slur and walk without hobbling even though the right side of her brain never actually recovered. She never regained sensation or the ability to control her left arm and it has become permanently paralyzed, demonstrating how even though the brain is elastic, it’s ability to adapt is not perfect. The chapter also discusses how a man by the name of Edward Taub experimented with monkeys to see how positive reinforcement in what’s he coined “shaping” during the period after a stroke known as “spinal shock” (when the neurons have trouble firing) could make it easier to relearn actions that were lost during the stroke. He concluded that use of the limb that’s been paralyzed made it much easier for the brain to adapt, not slings and disuse. 

Chapter 5 in particular did an excellent job of demonstrating how what we’ve been learning in class can be applied to and seen in the real world. This chapter tied together a previous unit from this class with our most recent unit, specifically the Cardiovascular Diseases (Part 2) Vodcast - in which we learned about how strokes occur - with the Brain Division, Specialization, and Adaptation Vodcast - in which we discussed brain plasticity and how the brain can reorganize neural pathways to make up for brain injuries. Bernstein suffered from a stroke, in which (as we learned in the Cardiovascular Diseases Vodcast) a blood clot forms in a blood vessel going to the brain. Thus, that part of the brain died, preventing the neurons in that section of the brain from receiving input and sending output. The neural pathways to that part of the brain had to (as we learned in the Brain Vodcast) reroute themselves to send sensory input to a different part of the brain that would then take over that particular function. Thus, this book really managed to bring together the various topics we’ve learned throughout the year regarding injuries to the brain and how neurons work to send signals to the brain.

Though - as seen from the inability of my grandma to regain the function of her left arm - the brain cannot self-heal every single brain injury for every single person, it most definitely does have plasticity. The plasticity is just limited. If I were to get the opportunity to ask author Norman Doidge two questions about his work I would ask him (1) what factors play a role in those limits - if a person has a healthier lifestyle, does their brain have more potential to reroute the neural pathways when they suffer an injury? What about age - do younger people have greater brain plasticity? Are there ways to modify one’s lifestyle in order to maximize the chances of having your brain self-heal when it gets injured? Also, (2) do genetics play a role in how elastic your brain is? If so, what factors in one’s family history or genetic makeup would make the brain have more plasticity? How could we design experiments or studies to find answers to these two questions?

I especially enjoyed reading the various ideas Doidge presents in this novel regarding Pascual-Leone’s theory that the brain’s anatomy can be changed with one’s imagination and the use of a transcranial magnetic stimulator (TMS) and the chapter about how neuroplasticity can be a curse when it comes to phantom pain from phantom limbs, in particular, because of how mysterious they are. Take the latter for example. Not much is known about phantom limbs but it was exciting to read how neurologists like V.S. Ramachandran have been working to try and see if phantom paralysis and pain can be “unlearned.” Doidge's work is most definitely not just theoretical because evidence of the phenomenon of neuroplasticity is clear and evident in the cases he discusses throughout the book.

This book is very credible and realistic because it is composed of actual stories and anecdotes from the lives of real people.The ideas about neuroplasticity that Doidge discusses in his novel have also been widely discussed by others in the medical world as it may have incredible practical implications for the future of neuroscience and neurosurgery. If we can figure out how to harness the power of the brain to reorganize neural pathways and then create surgeries and procedures modeled after it, we can make it much easier for people with brain injuries to regain functions that the injury ruined. In the future, such procedures could even render physical and occupational therapies useless. Such procedures and advancements in medicine made based on neuroplasticity would greatly benefit individuals in our society that have been handicapped by brain injuries and could soon have even greater applications when it comes to other mental disorders in which certain sections of the brain aren’t functioning properly.

Unit 6 Reflection

This unit was mainly focused on the brain, the senses, neurons, and disorders of the PNS and CNS. We talked a lot about how the brain is divided into major structures like the posterior pituitary, brainstem, hypothalamus, thalamus, cerebellum, and cerebrum, and then is further divided into more structures with their own specialized functions. We talked about brain lateralization, the important connection that the corpus callosum provides, and the different lobes of the cerebral cortex that aid in higher level thinking. See my blog posts on the Clay Brain Activity and Brain Dissection that we did in class to learn more about the anatomy and physiology of the brain.

To build upon the topic of higher level thinking, we read the article "How to Become a Superager," which discussed how the various regions of the brain have been categorized broadly into a cognitive region and an emotional region. Researchers found that extensive use of one's emotional region during younger ages can actually enhance their cognitive abilities later on in life. This was a pretty astonishing conclusion because the two regions of the brain were thought to be separate, but this demonstrates how the parts of the brain are actually very interconnected. It talks about how we must exercise all the regions of our brain, even when facing dilemmas or uncomfortable situations, because it helps develop a more healthy brain, which will have many advantages later on in life.

We also talked a lot about brain plasticity, a topic discussed further in a reading we did entitled "A Woman Perpetually Falling" (I posted a summary on a previous blog post here), which discussed how a woman named Cheryl lost the ability to stand without falling. This reading also talked about how she found a device that brought back her balance; however, soon she was able to walk perfectly without the brain. Overtime, the brain managed to redelegate the effected senses to other regions of the brain, demonstrating the elasticity of the brain. Feel free to check out my previous blog post for more information on this reading. 

A topic interconnected with our brain is our senses, the main ones being: vision, hearing, taste, touch, and smell. Each sense has different organs, receptors, and sensory cells that work together to take in sensory information in different ways, sent the information to the brain where it is integrated, and send back a motor signal, which we see as our response to the stimulus. To help us sense changes in the environment, we have special senses (which include sight, hearing, taste, and smell) because they have their own organ and somatic senses. The different types of receptors that take in the information has thermoreceptors which take in temperature, nociceptors which take in pain senses, photoreceptors which bring in light rays, chemoreceptors which sense chemicals, and mechanoreceptors that take in movement and pressure signals. See my blog post on the Sheep Eye Dissection to learn more about the sense of vision and how what we see is interpreted by the brain.

As we learned more about how the body interprets stimuli from its surroundings with its senses we read the article, "Fit Body, Fit Brain, and other Fitness Techniques." This article basically talked about how all types of physical activity actually help strengthen a person's memory and thinking abilities in their brain and help people stay strong later in life. It also talked about how exercise helped keep the white matter in a person's brain more in tact later on in life, which is extremely important because white matter is what is responsible for passing messages between different parts of the brain. Thus, the researchers in this article reached the conclusion that exercise can help improve and help develop certain parts of a person's brain and hence, improve his/her cognitive abilities, which is a huge motivation for people to start exercising more regularly.

We also read "How We Get Addicted" to learn how addictions like drugs and alcohol actually impair the brain's cognitive abilities by creating an all-consuming pattern of uncontrollable craving for the body. It discussed how the analytical regions of the brain generally evaluate the consequences of doing a certain action and override the mere pleasure seeking regions of the brain in a healthy brain; however, this fails to occur in an addict's brain. To see how specific chemicals in drugs thwart signals to the brain, we learned about neurons. The three main types of neurons in the body are sensory, integrative, and motor neurons, all of which have their own functions. The neurons are also divided further into the Central Nervous System (CNS) which includes the brain and spinal chord and the Peripheral Nervous System (PNS) composed of the spinal and cranial nerves that serve as communication lines. Various neurons work to pass information from the integrative neurons (with sensory receptors) to the integrative neurons (in the brain) to the motor neurons (that do some action) by passing chemical signals down the axon of one neuron, depositing the receptor into the synapse of the neighboring neuron and so on. We also did a Reflex Lab to reinforce what we had learned in the lecture about neurons and how they sense information from the environment to produce some action from the body.

This unit went pretty smoothly. A fan of dissections, I really enjoyed the Sheep Brain and Sheep Eye dissections and they were definitely one of my strengths in this unit. I learned so much from being able to see the organ in front of me and be able to visualize what the structures actually look like. As my VARK Questionnaire had revealed earlier this semester, I am a visual and spatial learner, so doing these dissections and making models with clay really helped me visualize the concepts we were learning and picture them clearly. A weakness I must admit is that there are so many concepts in this unit and so much material to understand and digest, that it was hard to put the concepts together and memorize everything while studying, however, lots of flowcharts and pictoral diagrams made it a little bit easier. Some unanswered questions I still have about the brain are: How does loss of function in certain regions of the brain (like with Cheryl in "A Woman Perpetually Falling") differ from the loss of functions for stroke patients? Are there only certain regions of the brain that are "elastic" and can be taught new functions - can only certain parts of the brain learn certain tasks? Are there certain tasks that cannot be relearned? 

Looking back at my New Year Goals, I can say that I've definitely improved on my confidence. Having performed in Bombay in the Bay this year for the fourth year in a row and seeing all the people in the audience looking back at me no longer scared me. In addition, by now I've had multiple college interviews - most of which went extremely well - and I think those helped me work on my confidence significantly. I tried my best to just be myself, remind myself to breath, and remind myself to stay calm, and for the most part, it worked really well. I can definitely say I've been making tremendous strides towards achieving this new years goal. Lastly, I'm still working on my goal to sleep earlier. As a second semester senior with a relatively more difficult class schedule than most of my friends, it's hard to find a balance between enjoying the "Second Semester Senior Life" and finishing all of my classwork on time and getting to bed on time. There definitely have been some days when I've managed to sleep by 11 or 11:30pm; however, they are very intermittent, and I need to work on making them more regular so I'm not a zombie in class. Looking back at my New Year Goals really made me realize that I need to refocus on meeting my goals and will start being more serious about finishing my work as soon as I get home so that I can get to bed earlier. 

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.