Unit 7 Reflection

In this unit, we learned about muscles and their function, structure, and how they contract in our body. First, we learned about directional terms of the body and joint movements of particular joints: flexion, extension, abduction, adduction, circumduction, rotation, pronation, supination, dorsiflexion, plantar flexion, inversion, eversion, protraction, retraction, elevation, depression, and opposition. Some of these only apply to certain parts of the body. For instance, inversion and eversion only apply to your feet, and circumduction can only be used to refer to limbs of the body. Next, we learned about the general muscular system and its functions: movement of bones or fluids, maintaining posture and body position, stabilizing joints, and heat generation. There are also four properties of muscle tissue: excitability, contractibility, extensibility, and elasticity. Then, we learned about the smaller components of muscle tissue, starting from the different kinds of fascia. First, the endomysium is the fascia that surrounds each muscle fiber. Next, the perimysium is the fascia that separates the muscle fibers into bundles. Then, the epimysium is the fascia that surrounds the entire muscle.

Furthermore, there are also different ends of the muscle, origin and insertion, which are the immovable and movable end of the muscle, respectively. In addition, we learned about the process of muscle contraction, which starts from the sarcomeres, the section of a myofibril where protein fibers overlap and slide past each other when muscles contract or relax. When a muscle contracts, the myosin and actin filaments in the sarcomeres slide past each other, using ATP and calcium ions in the process. Also, the process is started by a nerve impulse. My classmates and I made a video of the muscle contraction process:

In our next lecture, we learned about the different muscles in the human body and their specific names. In the head, there is the masseter and the temporalis, which both elevate the mandible. The trapezius controls the scapula, and the latissimus dorsi, deltoid, and pectoralis major all control the arm movement. Next, the biceps brachii and triceps brachii flex and extend the elbow joint. In the abdomen, the rectus abdominus and external oblique flex and compress the abdomen. Then, the external and internal intercostals elevate and depress the ribs. The diaphragm controls the lungs and allows for breathing, and the gluteus maximus controls thigh movement. The hamstring group of muscles is the biceps femoris, semimembranosus, and semitendonosus, all three of which control thigh movement and contraction. Next, the quadriceps muscles are the rectus femoris, vastus intermedius, vastus medialis/medius, and vastus lateralis, which control the thighs and knee joints. Then, the sartorius controls hip rotation and knee flexion, and the gracilis controls the thigh. The tensor fascia latae stabilizes the hip and the ilotibiial band stabilizes the knee laterally. Finally, the gastrocnemius, petroneus longus, and tibialis anterior all control the foot. My classmates and I identified the majority of these muscles in a chicken during a lab that you can see here (with photos): Chicken Dissection Lab

In our next lecture, we learned about muscle twitch and the three types of muscle fibers: slow twitch fibers, fast oxidative twitch fibers, and fast glycolytic twitch fibers. Every person has a different variety of these three fibers, depending on their level and type of exercise; exercise can even change the genetically-established variation of muscle fibers over a long period of time. There are also four types of muscle contraction: concentric, eccentric, isometric, and passive stretch. 

In our last lecture, we learned about performance enhancement substances, such as steroids and EPO.

Lance Armstrong took EPO.

 These substances are used to boost athletic performance, build muscle, aid in recovery, and lose body fat. All professional athletes are tested for these substances before major events due to their prevalence in the athlete community. Most of these PE-substances have serious risks that can even lead to death, so they should be taken appropriately. 

After this unit, I want to learn more about muscles atrophy, because I know that many young people do not exercise on a daily basis, including me. Is the process of muscle atrophy in young people the same as it is for seniors? My grandfather had trouble walking near the end of his life because he did not exercise regularly. 

Overall, this unit has been quite fulfilling and relatable, because we use our muscles everyday in every part of our lives. I think as a student I have become more well-rounded and supportive of my classmates, because for once I did not play the main role in a dissection. I am usually the main person dissecting because I thoroughly enjoy dissections and hands-on work. However, in this lab I simply took pictures and wrote notes and allowed my lab partners to take charge. This unit was quite fulfilling.