Muscular System

The muscular system is one of the various systems in the human body and it helps in the movement of all the body parts. It is made up of all the body skeletal muscles. Skeletal muscles are voluntary muscles under the control of premeditated actions. When an individual decides to make some movements, the brain sends a nerve signal to the muscle so as to initiate contraction for movement. Beside the skeletal muscles, there are other types of muscles such as the smooth and cardiac muscles (Jakab, 2006).

The difference between the two muscles and skeletal muscles is that they are involuntary. This implies that they are controlled by the nervous system and work without necessarily having to think about the actions they perform. The muscles in the body are identified depending on their functions, origin and attachment of the muscles, position or form in the body as well as how it resembles the object for which the specific muscle is used.

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There are several muscles in the body and they include deltoid which is the muscle that covers the shoulder joint, gastrocnemius which attaches to the bone of the heel, masseter for the purpose of biting as well as chewing, pectoralis major muscle which flexes, adducts and inwardly rotates the arm together with orbicularis oris among other muscles (STANFIELD, 2007). The muscular system takes the largest part of the human body and carries almost half the total weight of the body. These muscles are attached to the bone of the body skeleton.

The skeletal muscles are about 640 and they work together to initiate movements in various parts of the human body. This system is made up of layers of muscles that overlap. The outer is referred to as superficial muscles located under the skin while the inner layer is called deep muscles forming a layer under the superficial muscles (Jakab, 2006). Therefore, the objective of this research paper is to present the main features of the skeletal system and how the system helps in maintenance of homeostasis. It also includes a description of sarcomere contraction, disorders associated with the process and ways of treating the disorders.

1. 1 The muscular system The muscles in the body are divided into three namely cardiac muscles, skeletal or striated muscles and smooth muscles. Skeletal muscles are striated and can be consciously controlled or controlled by nervous system stimulation. On the same note, cardiac or heart muscles are striated but there is no conscious control over them. They can either be stimulated or inhibited by the endocrine or the nervous system. Conversely, smooth muscles are not striated but involuntary. Like the heart muscles, they can be controlled through stimulation or inhibition by the endocrine as well as the nervous system (Jakab, 2006).

The muscles are excitable in that they are capable of responding to stimuli by production of electrical messages. Besides, they are extensible, elastic and contractile. 1. 2 Homeostatic functions of the muscular system The muscular system together with other body systems works to maintain homeostasis. When skeletal muscles contract, heat is produced that helps to maintain the normal body temperature. For instance, when a person moves forth back while stamping feet during cold weather, warmth is generated.

Muscle movement produces heat which makes people to feel warm and this is apparent in case of shivering where muscles contract at an increased rate thus increasing the body temperature. The muscular system helps in consumption of water and nutrients in the body for maintenance of normal body temperature (Ehrlich & Schroeder, 2004). Muscle contraction also aids in the movements in lymphatic as well as the cardiovascular vessels. These contractions enable movement of blood back to the heart for oxygenation. In addition, the movement of the jaws as well as the tongue allows an individual to grind food using the teeth.

Voluntary muscle movements take place due to the contraction or relaxation of the skeletal muscles across a joint that freely moves. The skeletal muscles help in protection of the internal body organs and the strength of the muscles stabilize joint movements (Ehrlich & Schroeder, 2004). Besides, the skeletal muscles lower the diaphragm while raising the rib cage during breathing. Generally, the muscle primarily converts chemical energy in form of adenosine triphosphate into mechanical energy for performing work, movements and generation of force. 2. 0 Sarcomere contraction Muscle contraction takes place through small sarcomere contractions.

Sarcomere is a functional unit of a myofibril that is made up of two membranes acting as boundaries known as the Z-lines. Myofibrils refer to the rod-like units of muscle fibers that are protein in nature and are capable of contracting. The Z-lines are the points of attachment of the thin or actin filaments while M-lines are attachment points for the thick filaments also known as myosin. Contraction of the muscle results from the sliding of the thick and thin filaments over one another. Molecular motors drive the sliding process and this sliding causes the shortening of the sarcomere length (Sarcomere Contraction, n.

d). However, the length of the two filaments remains constant. Coordinated flexion of several heads of the thick myosin filament is required for the muscle contraction in large scale. The myosin heads interact with a large number of the active sites on the thin actin filament. Stimulation of the muscle fiber ensures that the cycle of cocking, attaching, flexing and releasing continues. Muscle contraction is stimulated by nerve impulses which bring about releases of neurotransmitters at the neuromuscular junction. This signals the contraction of the muscle fibers.

Calcium ions are also necessary for muscle contraction (Komi & International Federation of Sports, 2003). When the nerves are stimulated, there is an influx of calcium ions which frees thick filament binding sites on the thin filaments. This enables the formation of thin-thick filament cross bridges. Fig 1: Sarcomere contraction Source: Sarcomere Contraction Each of the cross bridges independently generates force which interacts with actin pulling it towards the sarcomeric centre (Komi & International Federation of Sports, 2003).

For instance, force is created by enabling the formation of the cross bridges which allows for empowerment of the repeated cycles by the energy stored in the adenosine triphosphate molecules. When this process is simultaneously repeated over and over by millions of the thick filament heads, it results in sarcomere contractions. Contraction of the sarcomere leads to myofibril contraction hence muscle fiber contraction causing bodily movements through large scale contraction of the skeletal muscles (SARCOMERE CONTRACTION, 2002).

Muscle contraction continues as long as the nerve impulses are stimulated and ceases when nerve impulse also ceases returning calcium ions to their stores. Muscles bring about movements in opposed direction by working in antagonistic pairs. An example of this movement is the case of biceps and triceps muscles. As biceps muscles flex the forearm, the triceps work to extend the forearm. 2. 1 Sarcomere contraction and homeostasis Sarcomere contraction causes movement of body parts which in turn fuel body functions. Body temperature is regulated through body movements such as exercises and walking, among other movements.

Muscular movements directed by sarcomere contractions enable people to chew and swallow food. If it were not for muscular movements, it would not be possible for blood to rush through various body parts. Continuous sarcomere contractions allow for appropriate circulation of blood in the body to support various functions taking place to support life. Breathing is also a function of muscle movement and digestion takes place because of muscular activity (Ehrlich & Schroeder, 2004). Overally, muscles would not be beneficial if it were not for sarcomeric contractions. 3.

0 Diseases and disorders Diseases and disorders that affect the structure of the muscles together with the disorders affecting motor neurons impair the functioning of the muscles. Neuromuscular disorders cause progressive loss of ability to move (Uversky & Fink, 2007). Some disorders are due to mutations of protein substances in the body while others involve normal injuries. In addition, there are diseases caused by pathogenic microorganisms. All these conditions work in unison to affect proper contractions of the sarcomere impairing the whole efforts of the body to move. 3.

1 Acute disorders These are common disorders of the muscular system such as injuries during sports and spasms which are sudden muscle contractions that are involuntary mostly accompanied by pain. The cramps are usually strong causing painful spasms, especially those occurring in the legs and foot. Muscle strains are muscular disorders resulting from injuries that cause the overstretching of a muscle close to a joint. They may result from engagement in a strenuous activity. A sprain is a joint twist causing injury and swelling of muscles, nerves, tendons as well as blood vessels.

Injuries involve tearing or overstretching of muscles and tendons. Management or treatment in cases of such injuries includes light exercises, rest and surgery in severe cases so as to ensure continuous impulse transmission (Marshall Cavendish Corporation, 2007). 3. 2 Autoimmune disorders There are a number of autoimmune disorders that affect the muscular system. An example is myasthenia gravis which is characterized by the inability of the muscles to respond to commands from the nervous system. In this condition, the neuromuscular junction is progressively destroyed.

As a consequence, the muscle cannot contract but becomes weaker and weaker. A common autoimmune disorder that mostly affects women is fibromyalgia. Face and neck muscles are the mostly affected parts where the ability to breathe, see as well as the ability to swallow is impaired leading to paralysis. Inflammations of this kind can be treated by application of drug therapies to suppress the affected parts and to counter the chemicals that are involved in the destruction of the neuromuscular junctions. In cases of multiple sclerosis, the myelin sheaths are destroyed by the immune system.

These myelin sheaths normally insulate nerve cells which control the muscles. This destruction affects the muscles by causing exaggeration of some reflexes in certain parts of the body while reflexes in other parts such as the abdomen are reduced. This can be treated by use of corticosteroids as well as other drugs for prevention of symptoms and slowing disease progression (Marshall Cavendish Corporation, 2007). 3. 3 Parasitic and Infectious diseases Several infectious diseases affect the muscular system. Myalgia is a condition that is accompanied by aching of muscles and is associated with viral infections such as influenza.

Moreover, poliomyelitis attacks the nerve cells causing muscle pain and even paralysis in severe cases. Effect on the respiratory muscles impairs the breathing system. In addition, tetanus releases toxic substances that obstruct sending of messages that prevent nerve transmissions. Absence of neuroinhibitors makes the cells to constantly switch on to trigger exaggerated spasms of voluntary muscles. Some of the muscles involved are the masseter muscles resulting in tight clenching which leads to inhibition of breathing and eating, among other activities.

Treatment of infectious and parasitic infections depends on the disease itself. The best treatment for tetanus is vaccination of individuals before the onset of the disease. Conversely, poliomyelitis has its own treatment. However, it can best be prevented by vaccinations (Marshall Cavendish Corporation, 2007). 3. 4 Involuntary contractions Spasms are sudden involuntary muscle tissue contractions while cramps are sustained involuntary muscle contractions that are painful. These conditions are caused by several factors including overuse of muscles, dehydration, injuries and electrolyte imbalance.

They are treated by use of drugs such as painkillers, doing light exercises and resting. Other involuntary muscle contractions include fasciculations which involve involuntary muscle unit contractions that are not part of the affected part. Fibrillations are another example of involuntary movements characterized by spontaneous muscle fiber contractions. These fibrillations may cause deterioration of the motor nerves. These conditions are best managed by treatment of the underlying disease conditions (Marshall Cavendish Corporation, 2007). 3. 5 Myopathies

These are disorder whereby muscle tissues fail to function appropriately leading to eventual weakening of the muscles (Uversky & Fink, 2007). There are some myopathies that may affect young children impairing the ability of the mitochondria to produce energy for movement purposes. Glycogen in the body may accumulate in the muscle tissues because of defects in the chemical pathways preventing the conversion of the glycogen into glucose. Glucose is required for fueling muscle contractions (Marshall Cavendish Corporation, 2007). Distal myopathies can be caused by mutations in the sarcomere.

The protein that is expressed in the thick myolin filament together with other factors such as gender may undergo mutation to cause the myopathies. Myopathies have no cure but supportive measures including orthotic appliances and physiotherapies can help. Perchance, diseases originating in the sarcomeric proteins could be countered by muscle transplants as successes in such trials may be beneficial in treatment of certain multiple mutations occurring in multiple genes (Laing, 2007). 3. 6 Tumors Tumors are another condition that affects effective transfer of messages for body movements.

There are tumors that can spread from one part of the body to the other and are referred to as cancers. Cancers of the skeletal muscles are found mostly in the arms and legs. However, the head, urinary tract, reproductive tract and the neck are also affected. Cancers are fatal if not given the appropriate treatment. Benign tumors can be easily controlled by administering the correct treatment. Nonetheless, they may also be deadly depending on the location of the tumor as well as the extent of the damage that they cause to the surrounding tissues.

Chemotherapy is available for cancers and benign tumors but prevention of these tumors is the best treatment (Marshall Cavendish Corporation, 2007). 3. 7 Muscular dystrophy This is a condition characterized by a progressive weakening and muscle degeneration. Muscular dystrophy is a term used to refer to a group of muscular disorders (Uversky & Fink, 2007). The dying muscle fibers are replaced by connective tissues and fat. The different types of the conditions vary depending on the body muscles affected, age as well as the rate at which the diseases progress.

An example of a common muscular dystrophy is Duchenne muscular dystrophy which is inherited when a mother carries a defective gene. The condition then occurs due to the lack of dystrophin protein production. This disorder mainly affects children resulting in deaths in children as young as twenty years of age. Death results from the inability of the muscles that aid in breathing to perform their function as the muscles become too weak to perform the intended functions. Muscular dystrophy patients need assistance in activities such as walking, positioning and exercises, among other motion exercises (Carter, 2007).

Other muscular dystrophies include limb girdle, myotonic dystrophy and Becker muscular dystrophy. Muscular dystrophies have no treatment. Nevertheless, physical therapies in addition to orthopedic surgery can be applied so as to slow the rate of disease progression and to improve the quality of life of the affected (Marshall Cavendish Corporation, 2007). 4. 0 Conclusion It is worth noting that the muscular system is very important in the human body. However, it cannot function alone to maintain the homeostatic functions but it works together with other systems of the body.

Within the muscular system are several functional processes that enable the system to accomplish the intended activities. Sarcomere contraction, being one of the functional processes in the muscular system, supports homeostasis and has several disorders as well as diseases that may occur affecting the normal function of the process. It is apparent that there are those diseases and conditions that can be treated while others cannot. Therefore, it is important to prevent such unhealthy conditions from occurring so as to avoid problems long term health problems and even death. References: Carter, P. J. (2007).

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(2007). Diseases and Disorders, Volume 2. New York: Marshall Cavendish. SARCOMERE CONTRACTION. (2002). Retrieved July 21, 2010, from http://163. 16. 28. 248/bio/activelearner/38/ch38c6. html Sarcomere Contraction. (n. d). Retrieved July 21, 2010, from http://www. unc. edu/~scmannin/greg. html STANFIELD, P. S. (2007). ESSENTIAL MEDICAL TERMINOLOGY. New York: Jones ; Bartlett Learning. Uversky, V. N. , ; Fink, A. L. (2007). Protein misfolding, aggregation and conformational diseases: Molecular mechanisms of conformational diseases, Part 2. New York: Springer Science + Business Media, LLC.

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