What Happens When You Stretch

Relate & Review:
As we learned previously through our notes and a video, muscles are comprised of segments called sarcomeres. These can contract and elongate according to whether the muscle is relaxed or engaged. When we stretch, our sarcomeres elongate until each one is fully stretched and the muscle fiber is completely relaxed, then collagen fibers in connective tissue "pick up the slack" and pull in the same direction as the stretch. The main nerve endings in muscles are proprioceptors (mechanoreceptors). Like Mr. Orre said, these tell your where you are in space. Basically, if you close your eyes and lift your arm, the proprioceptors tell you how high your arm is raised. They are present in all nerve endings of joints, muscles, and tendons. Muscle spindles are the most prevalent proprioceptors in the muscles. The muscle spindle stretches when a muscle is stretched and triggers an action called the stretch reflex, which contracts the previously stretched muscle. However, this reflex can be reduced through prolonged and frequent stretching. This article mentions dancers as some of the few humans that possess very little to no stretch reflex, as they stretch like crazy.
Quotes:
"While this type of control provides the opportunity for the greatest gains in flexibility, it also provides the greatest risk of injury if used improperly." (2)
- This quote was interesting to me as it shows the potential risks for pushing your body to the max in order to reduce your stretch reflex. I think this shows the lengths dancers are willing to go to in order to further their careers. It is sad that so much is expected of people so that they can stand out and be better.
"Just as the total strength of a contracting muscle is a result of the number of fibers contracting, the total length of a stretched muscle is a result of the number of fibers stretched -- the more fibers stretched, the more length developed by the muscle for a given stretch." (1)
- Strength and flexibility are inversely related based on sarcomere length. This unit is still blowing my mind as I never even knew sarcomeres existed beforehad, I just thought the muscle as a unit would move like pulling taffy at a candy shop. Now it makes more logical sense. 
"Another reason for holding a stretch for a prolonged period of time is to allow this lengthening reaction to occur, thus helping the stretched muscles to relax. It is easier to stretch, or lengthen, a muscle when it is not trying to contract." (3)
- I have witnessed this firsthand! It's the coolest phenomonon. I remember sitting in the splits hating life as I couldn't get all the way down, and I was clenching all my muscles, then all of a sudden, my hamstrings just relaxed and it was way easier. 

Build a Better Hip Joint

Abstract:

A common problem for athletes, especially athletes like dancers and gymnasts who place major stress on their hip joints, is Snapping Hip Syndrome, or the snapping movement of a muscle or tendon across a bone. I propose a solution in order to reduce this condition: laterally running tendons connected to these muscles and tendons that help alleviate the stiff movement and support them as they move across the bone as well as bigger bursa to reduce friction.

Main Body:

The Hip Joint:

The hip joint is arguably one of the most important joints in the body. Without it, humans would be confined to sedentary lifestyles, as we would be unable run, walk, jump, or bend the knees. It is an extremely movable and flexible joint, which is especially evident when dancers perform kicks such as battements. The hip is a ball-and-socket synovial joint. The two bones connected in the joint are the hip bone, also known as the pelvis or the scientific name os coxa, and the thighbone, or femur. On the ischium, or lower bone of the pelvis, there is a cup-shaped socket known as the acetabulum. The femur’s rounded epiphysis is the ball part of the joint. The joint is lined by hyaline cartilage, which covers both the acetabulum and the epiphysis of the femur. The hyaline cartilage is vital in providing a smooth surface for the bones and also in absorbing shock. The hip joint also has another layer of protection in the bursa, a sac filled with synovial fluid and lined by a synovial membrane to further lubricate the joint. The hip joint is surrounded by dense ligaments to prevent dislocation, such as the iliofemoral ligament and the pubofemoral ligament. The iliotibial band, or IT band, runs on the outside of the hip joint all the way down to the knee. The iliopsoas tendon connects to the inner thigh. Near the ball of the femur is the femoris tendon. The hip joint allows for an extraordinary amount of movement, allowing for 360 degree circumduction and an almost 90 degree lateral axis. It is also extremely tough, as it endures multiplied force during activities such as running.

The Problem:

A common condition that occurs with athletes such as dancers and gymnasts who put repeated intense stresses on their hips is Snapping Hip Syndrome, also known as Dancer’s Hip. This is a medical condition in which a muscle or tendon incorrectly and rapidly moves across a part of the hip bone or the top of the femur, causing a popping or snapping sound and sensation. This is what you hear when a ballerina lifts her leg, and commonly sounds like a “crack.” This condition is difficult to prevent, as it occurs in most athletes that must keep up the demand on their bodies. While usually painless, prolonged cases of Snapping Hip Syndrome can lead to bursitis, or inflammation of the bursa.

The Redesign:

The main problem with snapping hip syndrome is that the movement across the bone by the muscle or tendon is too sudden and uncontrolled. To combat this, I propose the addition of two tendons that run horizontally across the muscles and tendons. This way, the moving muscles and tendons will have extra support running in the direction of their movement that will prevent the erratic snapping. These new tendons will share the blood and nutrient supply of the muscles and tendons they support, although the number of capillaries may need to be increased to keep up with increased blood demand. I also believe the size of the bursa should be increased in order to prevent friction.

Discussion:

Growing up as a dancer, I am all too familiar with Snapping Hip Syndrome. Almost every class during plies, at least three girls’ hips would loudly “pop,” sending the rest of us into a fit of giggles. Dance places a lot of pressure on your hips, as you’re expected to be able to lift your leg past your head and turn out your feet past a natural level. While at the time the condition seems harmless, more annoying than anything else, after time it can cause pain and inflammation that may not go away for a while. I know two people already who have needed hip surgery before the age of 20 from dance. This is worrisome as they will have to deal with repercussions from this condition for the rest of their lives. My proposed design was intended to help make the movement across the bone more natural. Because the snapping movement is erratic and rapid, the two tendons that run laterally will help smooth the movement out and control its speed. A problem may be how those tendons get nutrients from the body. While right now I believe that these tendons could share entry points and capillaries with the existing muscles as they could just be very small in comparison, this may not be enough to nourish the tendons. This assignment was semi-difficult to make plausible. The human body is complex already, so trying to make a complex joint even more specialized was a challenge. While there currently is no way to prevent Snapping Hip Syndrome other than not participating in certain sports, there are some ways to prevent further damage. Some ways include reducing the intensity of activity, icing the affected areas, or taking pain relievers to reduce inflammation.

Works Cited:

Biel, Andrew. Trail Guide to the Body: How to Locate Muscles, Bones and More. Boulder, Colo: of Discovery, 2008. Print.

Taylor, Tim. "Hip Joint." InnerBody. Innerbody.com, n.d. Web. 09 May 2017.

Zelman, David. "Snapping Hip Syndrome." WebMD. WebMD, 21 Apr. 2017. Web. 09 May 2017.

Unit 7 Reflection

This unit, we dragged the skeleton out of the (supply) closet and learned all about bones! The skeleton is actually an organ system called the skeletal system, and while at first, it may seem like bones are relatively inanimate, bones are actually constantly undergoing change and vital processes.

The different types of bone cells.
Image courtesy of Wikipedia Commons.

Let us first examine the anatomy of a bone on a microscopic level. Within the bone, there are osteogenic cells, and conveniently, "Osteo" means "Bone" in Greek. Obviously, our bones don't stay the same size throughout our entire life, otherwise, we would remain baby-sized forever. We actually undergo a process called ossification, or osteogenesis, in order to remodel and grow our bones. This process takes place from fetal development to around 25 years old, when our bones are completely ossified. This utilizes two types of cells: the osteoblasts and osteoclasts. Osteoblasts are the bone-building cells, and osteoclasts are the bone-destroying cells. Together, they work in harmony to remodel the bone in a constant state of flux. As old bone is destroyed, new bone is formed, keeping our bones nice and fresh. In fact, we create an entirely new skeleton approximately every 7 years! Mature bone cells are called osteocytes, and they conduct the daily processes of bones to maintain homeostasis. Bones have a compact bone exterior that is hard and dense, and a spongy bone interior that is more porous and filled with bone marrow/blood vessels. Through the Haversian Systems, osteons, or cylindrical canals, contain the bone's blood supplies. They are surrounded by lamellae which run perpendicularly to the osteons in order to provide more sturdiness. The lacunae are small spaces in the bone that contain the previously mentioned osteocytes.

Now we will look at bones on a macroscopic level, as well as discuss the different types of classification of bones. Bones can be classified into 4 different groups: long, short, flat, or irregular. Long bones are longer than they are wide, like the femur. Short bones are cuboidal shaped, like the carpals in your hand. Flat bones are, well, flat, like the ribs or the sternum. Lastly, irregular bones are the bones that don't fit into any other category, like the odd-shaped pelvis. In the skeleton, there are also joints that allow for movement in our bodies. Fibrous joints are surrounded by dense connective tissue and are synarthrosis, or immovable. An example would be the sutures of your skull. Cartilaginous joints are surrounded by cartilage and are amphiarthrosis, or allow for little movement. Synovial joints are the joints we typically think of, and they are surrounded by a joint capsule containing synovial fluid. They are diarthrosis, or fully moveable, and include joints like your elbows. To see a fun activity where we examined and classified bones on our own of rodents, refer to the Owl Pellet Lab.  

Owl Pellet Lab

In this lab, Michelle and I analyzed an owl pellet, which is the regurgitated remains of a barn owl's meal (a yummy rodent or bird) that could not be digested. When we first unwrapped the pellet, it looked like a lump of fur. It felt like I was petting my old pet hamster. After we began examining the inside and carefully crumbling away the dark fur parts to expose the bone, it was evident that we had multiple rodents in our pellet, as shown by the 11 humerus and femur bones we found. We believed we had vole bones in our pellet. Our reasoning for this was: the shape of the humerus bones, which were long but thin and had the defining triangle spike on the side; the shape of the tibias and fibulas, which were fused in our case; and most notably the shape of the skull pieces, which had the large sharp front teeth and the tiny back teeth, as well as the deeper eye socket. These characteristics clearly point to a vole, as the other rodents ehad differently shaped humerus bones (the shrew's lacked the spike on the side and the mole's was vaguely circular), fibulas and tibias, or skulls (the shrew had an indiscernible eye socket, and the mole's was also more shallow).
The bones we found had some similarities and differences to a human skeleton. The human humerus is also in the shape of a long line. Both the vole and the human humerus has two wider epiphyses at each end of it. The skull also has the same basic features, such as an eye socket, the sharp teeth like the canine teeth in humans, and the flat molars near the back of the jaw. However, the vole has the distinct triangle on the side of the humerus, which humans lack. The radius and ulna are also very different in the vole, with the ulna being remarkably thin in comparison to the radius. (Maybe vice versa.) The tibia and fibula were also fused in the vole and not in a human.

Unit 6 Reflection

This unit covered the sense and the brain, beginning with the overall anatomy of the brain then going more into depth on the function of each part of the brain. We then covered the two hemispheres and lobes of the brain. The right hemisphere focuses on overall context, while the left brain focuses more on specific facts and details. The brain is also very flexible and adaptable and can heal from trauma or in response to new stimulation. We then moved onto our 5 senses and how the brain receives and reacts to sense stimuli, through sight, hearing, touch, taste, and smell. For example, the brain contains proprioceptors to sense pain and thermoreceptors for heat. Neurons send signals from the external stimuli to the brain, through integration in either the Peripheral Nervous System or the Central Nervous System. Each different system represents a section of the overall neural system and plays an important role in integrating messages and responding to the motor neurons to perform a reaction.

This is the analysis of the sheep brain dissection lab we did this unit, and here is the sheep eye dissection lab. Both were engaging and helped me really understand the location of each part of the brain or eye.

We read many interesting articles this unit. The first was "How to become a Superager" by Lisa Barret.This article was about how older people called "superagers" are able to function and have the same brain capacity of that of young people. While they might look old physically, mentally they are still functioning at their peaks. To keep the brain at this level of function, you must engage it through solving challenges, exercising, and doing difficult problem solving beyond simple sudoku. The second was "Fit Body, Fit Brain, and Other Fitness Trends" by Gretchen Reynolds. She explains how exercise also helps to keep our brain fit, most notably through an increase in neurons. She mentions studies that show how weight training can lead to fewer lesions in the brain's white matter. She also discusses how in a set of twins, the twin with more muscle mass has a stronger brain in the future.  We already knew exercise is super important to staying healthy, and this just reaffirms that. The last article we read was "How We Get Addicted" by Michael D. Lemonick, a former addict and alcoholic who overcame his addiction. Humans innately want to feel pleasure, which explains why they've turned toward drugs since the beginning of time. Drugs create a salience overdrive, causing an uncontrollable desire that turns into a severe craving. In addicts, the reasoning part of our brain that tells us, "Hey, drugs are bad!" doesn't function correctly, allowing them to continue in a negative cycle of addiction. This unit has been hard, but this time of the year is never easy for me. It's hard because I'm not trying to be the typical senior who flakes on responsibility second semester, but I just feel overwhelmed and emotional all the time. It's not like I want to feel like this or that I'm actively trying to be a bad student, but it's difficult to balance and prioritize things when I feel like I can't focus on anything but the negatives. 

Reflex Lab

In the reflex lab, we tested different reflexes on our lab partners. These reflexes included the photo pupillary reflex, the knee-jerk (patellar) reflex, the blink reflex, the plantar reflex, and our general response time in reaction to a stimulus. In essence, a reflex occurs on an arc, the most simplistic one being monosynaptic. That means the reflex has only two neurons: a sensory neuron and a motor neuron. Most reflexes, however, tend to be polysynaptic, containing multiple relay neurons in between. Most sensory neurons synapse in the spinal cord rather than the brain, allowing for a quick reaction time without the need for transferring information to the brain.
Claims Evidence Reasonings:
The photo pupillary reflex is when the pupil dilates in response to a changing environment. The evidence of this reflex is visible in the video we took of Michelle's eye after shining a flashlight into her eye that had been deprived of light for two minutes prior. Her pupil clearly increases size. This is a response that controls the amount of light entering the eye and adjusts rapidly to quickly adapt to a changing external environment, allowing for humans to see faster to react to any threats.
The patellar reflex is a contraction of the thigh muscle in response to a light tap below the kneecap. We know that a mechanoreceptor sensory receptor felt the pressure of the tap and in turn, through a monosynaptic reflex to the spinal cord, the thigh muscle contracted to kick the foot forward. We saw this happen after Hayley and I took turns tapping each other below the knee, and each time our feet involuntarily lifted. We found out that this occurs as a way to allow humans to catch their balance: the contraction of the quads puts the torso back upright during a falling motion.
The blink reflex is the closing of the eyelids in response to a rapidly approaching object, whether it touches the eye or not. When I threw the cotton at Hayley, she not only blinked, but she flinched too. Same with when I pretended to punch her. ;) The reasoning for this reflex is so that no foreign objects get in the eye.
The plantar reflex is the clenching of your toes when something drags along the bottom of your foot. When Hayley dragged her pen across the sole of my foot, I not only giggled and squirmed as I am severely ticklish, but my toes also clenched inward. I think the reasoning for this is that when your foot feels the ground while you're running, your toes clench downward to allow for more grip on the ground to propel you forward in your run.
Our response time was the time it took to react to a stimulus, in this case, a falling ruler. Hayley had the faster average response time, at 0.20 seconds. However, after we introduced texting into the experiment, both of our reaction times slowed significantly, with hers slowing to 0.30 seconds. This is because it's extremely difficult to multitask and devote attention to both texting and catching the ruler.

Sheep Brain Dissection Analysis

My rendition of the surface of the brain.

The sheep brain before any incisions.

In this lab, we dissected a sheep's brain to observe the different sections of the brain and how they work in relation to each other. As we learned before, the brain is divided into different sections. By simply observing the surface of the brain, we can distinguish a few structures, including the cerebrum, which is the front parts of the brain, the cerebellum or bell-shaped lump near the back of the brain, and the brainstem, which protrudes out of the back and bottom of the cerebellum. The cerebrum controls higher brain function, such as thought and action. The cerebellum receives sensory information and regulates voluntary movement, like posture for example. The brain stem controls the flow of messages between the brain and the rest of the body, while also controlling basic bodily functions like breathing.

After making a longitudinal incision to sever the brain into two halves, the right and left hemispheres, even more structures became apparent. What looked like a mere chicken cutlet at first glance now became a complex and organized network of thoughts, each specialized part of the brain controlling its own important part of the sheep's life. Now we could see myelin layers, which appeared as a paler color than the surrounding brain tissue. You can clearly see a
tree-shaped branching bunch of myelin fibers in the cerebellum. Myelin acts as an insulator on the neurons to speed up the process of interpretation, which is why it concentrates in areas of the brain that require ultra-fast processing, like the cerebellum, which I thought looked a lot like cauliflower. We observed the corpus callosum, which was the only thing connecting the two hemispheres, allowing for communication between the two. This is what was severed in split brain patients. We also saw the midbrain, the collective of multiple structures involved with the central nervous system, vision, hearing, etc. Towards the front of the brain was the optic nerve, which transfers visual information from the retina to the brain. The first lump, going from the posterior to the anterior of the brain, was the pons, which controls breathing, communication, taste, hearing, balance and more. The next bump was the medula oblongata, the regulator of breathing, heart and blood vessel function, digestion, sneezing, and swallowing. In front of that was the thalamus, which correlates consciousness, sleep, and sensory interpretation, and then the hypothalamus, which connects the nervous system to the endocrine system through the pituitary gland and the hormones released from it. After making a cross sectional cut, we could see even more clearly the aforementioned myelin, whose presence created white matter. The darker brain matter is called grey matter.