Biology fundamentals and core concepts

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Muscles are an important part of our body, and without muscles, one would neither be able to walk nor to talk, and, quite literally, the blood would stop flowing within the body if our muscles did not work. In fact, muscles can be referred to as the 'engine' within our body, which we utilize in order to 'propel' ourselves by converting 'energy' into 'motion'. Anything that the brain conceives of doing is in fact carried out by muscles, and since they are long lasting, as well as self healing, and will keep growing stronger if they are used more, they form an incredibly sophisticated piece of machinery within the living body, and must be treated as such. There are three unique types of muscles within a mammal's body, and these are: the skeletal muscles that contract voluntarily, and are attached to the skeleton and come in pairs, the smooth muscles of the digestive system, etc., that contract involuntarily, and the cardiac muscles of the heart, which are also involuntary muscles. (Freudenrich, How Muscles Work)

The basic function of any muscle is that of 'contraction', and a muscle is generally made up of a bundle of 'fibers'. A fiber in turn contains numerous 'myofibrils', or in other words, 'muscle proteins', which allow the muscle to perform its task of contraction. Within the myofibril are two types of filaments, thick, and thin, which are attached to a 'Z-line'. The myofibril that is attached from one end of the Z-line to another is known as the 'sacromere'. When the myosin, or the protein found within the thick filaments, which, when taken in molecular terms, is nothing but a shaft of myosin molecules arranged in a cylindrical shape, grab on to the thin filaments, which are, in turn made up of another protein known as 'actin', then a 'cross bridge' would be formed. The thick filaments end up pulling the thin filaments past the bridges, and this makes the sacromere shorter. What is important is that within a muscle fiber, the signal for contraction of the muscle is synchronized so that all the myofibrils making up the sacromere are shortened at the same time, simultaneously. (Freudenrich, How Muscles Work)

Question: 2

Although it has been stated by scientists and those of the medical profession that it is not possible for the spinal cord of the mammalian body to be able to function independently of the brain, and that without receiving messages from the brain, the spinal cord would not be able to inform the muscles of the body on what to do next, it was after the actor Christopher Reeve's horrendous injuries when he happened to fall off his horse that scientists began to conduct research on whether or not the spinal cord would be able to function without getting messages form the brain, and what they discovered was fascinating. VR Edgerton was one scientist who began his research by cutting the spinal cords of cats midway down their backs, and putting them on a treadmill, the purpose being to find out if the cats would be able to mimic real walking by means of inducing repetitive activity in such a way that the activity would be able to reawaken certain circuits that had been shut off by the injury to the spines. The experiment showed that these animals could indeed be made to walk again. (The Reeve Effect: Can an actor's determination to walk again change the way medical research is conducted?)

Another important fact discovered by the experiment was that when there was an injury to the spinal cord, amino acids flooded the area, and with the repetitive activity on the treadmill, these amino acid levels dropped, and this meant that the area could be trained to respond differently. In addition, it was also discovered that it would be possible to train one network at a time. In conclusion, Edgerton stated that the neural structure within the lumbar cord was a 'central pattern generator', which not only directed the subconscious into walking, but also stored the memory of walking within, so that it could be activated, after injuries, with rehabilitation and training. (The Reeve Effect: Can an actor's determination to walk again change the way medical research is conducted?)