Biological Basis for Human Movement - Essay Example

Lab Report: Biological Basis for Human Movement The purpose of this report is to study two skeletal muscles, the gastrocnemius medialis and the tibialis anterior. First, it is necessary to properly describe the arrangement of muscle fibers for each of these two muscles. It is important to note that both of these muscles are pennate but are different in some ways. The Gastrocnemius is a large muscle in the back, lower portion of the leg (part of the "calf). The tibialis is located in the front, lower portion of the leg and runs along the tibia or shin bone. The tibialis is mainly used for extension and ankle dorsiflexion. These types of movements are not particularly powerful movements but an important one none the less. The tibialis is responsible for ensuring that the toes are lifted properly during the act of walking. Without this, the foot would constantly drag. The gastrocnemius on the other hand is made up of two thick muscle bellies (composed of muscle fiber bunches) and is responsible for flexing the foot while the knee joint is extended. Comparatively speaking, the gastrocnemius is a larger more powerful muscle than the tibialis anterior. The gastrocnemius is composed of more fibers and contains two muscle bellies as apposed to one. To better understand theses two specific muscles, one must first establish the cellular structure of muscle tissue. Muscular tissue is considered to be contractile or possessing an elastic property, similar to a rubber band. Muscles are made up of certain types of cells called muscle "fibers". These specific types of cells are composed of what is called actin filaments and myosin filaments. It is the interconnecting or interacting of these filaments that is responsible for muscle contractions. The specific types of muscles that this lab is concerned with are called skeletal muscles. These muscles can also be called striated muscles. The term "striated" is given them due to the thread like fibers that they are composed of, which are both light and dark. The appearance of light and dark in these muscle threads is due to the actin and myosin filaments. These thread like fibers cause the muscles to appear striped or "striated". Skeletal muscles are responsible for the movement of limbs and appendages. They are attached to the long bones via tendons. It is the angle that presents between the joint and the muscle that constitutes the angle of pennation that we will be studying. In the observation of these muscles, we need to understand their structure on a cellular level in order to fully comprehend their mechanisms. It is important also to know that each of the skeletal muscles that we are observing is made up of several muscle fibers (cells). These fibers are each a long cell with some unique cellular characteristics. One of the characteristics specific to muscle fibers (cells) is the sarcolemma. The sarcolemma is the plasma membrane to the muscle fiber (cell) with some very important features. It possesses what is called T tubules which are structures specifically for penetrating the cell itself in order to make contact with the sarcoplasmic reticulum. These tubules aim to touch the sarcoplasmic reticulum without actually connecting to it. The sarcoplasmic reticulum is much like an endoplasmic reticulum but an enlarged or expanded version. The sarcoplasmic reticulum is larger or expanded in muscle fibers in order to store calcium ions. Calcium ions are imperative to the contraction of muscles. The part of the muscle fiber responsible for contraction is called the myofibril. Structures called sarcomeres are located within these myofibrils. The sarcomeres contain protein filaments which is the core reason for muscle contraction. This is basically the contraction site of the muscle. The protein filaments are composed of the two filaments mentioned earlier, actin and myosin. The interaction of actin and myosin can be explained by what is called the Sliding Filament Theory. This theory states that during the contraction of a muscle, sarcomeres become shorter. Since the sarcomeres contain actin and myosin filaments, it is these filaments that are literally sliding together. At this point, it is necessary to describe the results of the lab exercise that corresponds to this paper. This exercise was performed to essentially measure muscle length at rest and during a contraction to then compare the difference. We are seeing with this exercise on a macro level, the shortening of the skeletal muscles during voluntary muscle contraction. We are also able to assess the pennation angle at rest and during voluntary movement and compare the difference. During this lab exercise, we were asked to measure resting and moving fascicle lengths as well as resting and moving angles of pennation of both the gastrocnemius medialis (GNm) and the tibialis anterior (TA). These measurements were taken by using in vivo ultrasound images. During the imaging, we were also asked to identify the aponeuroses of both muscles. The two individuals that were used for this exercise were Nicky and Jim. The following data was recorded from their in vivo results. Nicky was the first to undergo ultrasound. The first muscle observed was the TA which had a resting fascicle length of 69mm, 70.7mm and 78.1mm with an average of 72.6mm. In contrast, the same TA muscle in motion had a fascicle length of 48mm, 42.7mm and 46.5mm with an average length of 45.7mm. The difference in Nicky's TA fascicle length from resting to motion is roughly 26.9mm. In looking at the same TA muscle on Nicky via ultra sound, we observed that her resting TA pennation angle was 6.57 degrees, 5.19 degrees and 4.63 degrees with an average of 5.66 degrees. Inversely, when in motion, Nicky's TA muscle showed pennation angles of 21.26 degrees, 19.87 degrees and 19.67 degrees with an average of about 20 degrees. So far, we can deduce that in motion, the TA muscle shortens due to contraction. As the TA muscle contracts and becomes shorter, the pennation angle becomes larger. Next, we can examine similar results on the gastrocnemius medialis, still using Nicky as our subject. At rest, the fascicle lengths of Nicky's GNm was 46.89 mm, 47.35mm and 46.27mm with an average length of 46.83mm. Looking at the same muscle on Nicky but in motion, we find fascicle lengths of 25.1 mm and 24.3mm with an average of 24.7mm. This is about half the length of the GNm when it is at rest. Again, we are observing a significant difference is size from the resting muscle to the moving muscle. To look at the angle of pennation of the same muscle on Nicky, we find resting angles of pennation to be 17 degrees, 19 degrees and 18.6 degrees with an average of about 18 degrees. When moving however, the same muscle can be measured as having angles of pennation at 31.8 and 37 degrees with an average of about 34 degrees. This is about 14 degrees greater than the angle of pennation of the same muscle at rest. Next, we considered the same two muscles on Jim. First we will look at the TA muscle and discover the fascicle lengths at rest. These lengths came to 75.9 degrees, 78.7 degrees and 84.4 degrees with an average of about 80 degrees. Looking at the same TA muscle in motion, it was established that the results were inconclusive. The lengths came out to 79.0mm and 76.1 which is virtually the same as the resting length. This is inaccurate as the length during motion should be closer to half of the resting length, not equal. It is possible that the muscle was not made to contract or that the machine was not calibrated correctly. In looking at the angle of pennation in the TA muscle of Jim's, we do see results that we would expect to see. The angles of pennation came out to be 14.88 degrees and 14.93 degrees which is about twice the degree of pennation of the resting TA muscle. In observing Jim's GNm muscle, we found that at rest, it measured 43.32mm and 43.08mm with an average of 43mm. Conversely, at a contraction state, the same muscle was measured at 27.84mm and 31.4mm with an average of about 29mm. When at rest, the same muscle had a pennation angle of 22.18 degrees and 22.17 degrees averaging out to 22 degrees. At motion, the same muscle showed an angle of 25.15 degrees and23.24 degrees with an average of about 24 degrees. This is not the result that was expected as the angle of pennation was expected to be somewhat greater. The expected result was an angle of pennation at about 34 degrees or more. This however does not mean anything other than there was not real change in the space between the aponeuroses. Aside from the data that has been determined inconclusive, we can say based on these results that in both the TA and GNm muscle, one can expect the muscle to decrease in size by as much as half during a voluntary muscle contraction. One can also expect a corresponding angle of pennation in that as the muscle decreases during motion, the degree of pennation can increase up to about 30 %. Works Cited Marieb R.N., PhD, Elaine, 2000, Anatomy and Physiology, Pearson-Benjamin Cummings http://jap.physiology.org/cgi/content/full/90/5/1671 http://jap.physiology.org/cgi/content/full/90/5/1671 Mader, Sylvia, 1998, Biology, McGraw Hill, New York, New York Read More