Deprived Oxygen Cells Research Paper
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Adenosine triphosphate (ATP) is considered the major energy source of the body and like in any other system, it is used to initiate and carry out a contraction of a muscle or group of muscles. This contraction causes body movements and maintenance of equilibrium. For a contraction to take place, a large amount of energy is broken down from ATP to Adenosine diphosphate (ADP). The amount of breaking down of ATP into ADP is directly proportional to the amount of work on a muscle. This has been postulated as Fenn effect. The presence of Adenosine triphosphatase (ATPase) enzyme on the myosin head facilitates this cleavage of ATP into ADP. Simultaneously, calcium ions merge with troponin-tropomyosin complex and causes exposure of binding sites on actin filament for myosin head to get attached. A conformational change occurs that causes the striking force to pull the actin filaments. This tilting of the head causes release of ADP and phosphate already bound to the head. The new molecule of ATP gets attached after the separation of head from the actin and the process is repeated. It becomes evident from above mentioned details that, a constant supply of ATP is required to meet the energy requirements of a muscular tissue. (Guyton and Hall, 2006, p.78)
Eroschenko and Fiore (9th ed., 2000, p 117) describes the histological arrangement of the skeletal muscle cell. Fibres of skeletal muscles are long, cylindrical and have many peripherally located nuclei. The basic unit of these fibres is a myofilament which consists of actin and myosin. Actin and myosin are proteins that are contractile in nature. They are arranged systematically in a cross striation pattern. This cross striation is labelled as lighter I bands and darker A bands under light microscope. This gives skeletal muscle another name, striated muscles. On electron microscopy, it may be observed that I bands are cut in half by Z line. The area present between two consecutive Z lines represents the sarcomere, which is the smallest contractile unit. The general overview of muscle cell histology is pivotal in understanding the mechanics of muscle contraction which is described in the subsequent text.
Muscle acts as cellular machinery that is able to transform chemical energy into the mechanical energy. The main chemical source is ATP which comes from the metabolism of lipids and carbohydrates. (Barrett, Boitano, Barman and Brooks, 2010, p102)
Barrett, Boitano, Barman and Brooks (2010, p103) describes the energy consumption during different degrees of exercise and the source of raw material for the energy. Mild exercise and resting muscle tissue uses fatty acids as their energy source that is formed by the lipid metabolism. But, these lipids fail to meet the energy requirement whenever there is increase in the intensity of exercise. The rapidness of muscle contraction and its energy demand is only met by carbohydrates at that time. Carbohydrates basically split into carbon dioxide (CO2) and H2O while glucose is degraded to pyruvate in the blood. Pyruvate is also present in the stored form of glucose, called glycogen which is present in the liver and skeletal muscles. In an O2 deprived state, the pyruvate that is formed by the metabolism of glucose is not entered into Tricarboxylic Acid (TCA) cycle. Instead, it is reduced to another entity called lactate which has high energy yielding, oxygen independent phosphate bonds but in smaller amount. This process is called anaerobic glycolysis.
It has been postulated that among other things, rate of delivery of O2 to the peripheral tissues or to the lungs limits the exercise. Lactate accumulation gives rise to a feeling of fatigue. The capacity of an individual to exercise is reached when this feeling is turned into exhaustion. This fatigue is brought by the neural impulses from muscular tissue, accumulation of lactic acid decreasing the pH, rise in body temperature, difficulty breathing and the feeling of discomfort produced by J-receptors activation of lungs. (Barrett, Boitano, Barman and Brooks, 2010, p637)
The muscular tissue is dependent upon the uninterrupted and ample supply of energy to carry out contractions. This contraction helps human body to maintain a posture and equilibrium. It provides mobility as well. The energy used depends on the activity of the muscle. Vigorous exercises need a lot of energy beyond the capacity of human stores for aerobically synthesized ATP. The demand is then fulfilled through production of lactate which does not require oxygen supply for its synthesis. Everything has a price and excessive lactate can have deleterious effects on human body pertaining to its nature to reduce the pH and cause acidosis. The sensation may start from feeling of fatigue and moving on to exhaustion and difficulty breathing.
Barrett, K., Boitano S., Barman S., & Brooks H. (2010). Excitable Tissue: Muscle. In Ganong’s Review of Medical Physiology (23rd ed., pp. 102-104,637). New York: McGraw-Hill Medical.
Eroschenko, V., & Fiore, M. (2000). Muscle Tissue. In Di Fiore's Atlas of Histology with Functional Correlations (9th ed., p. 117). Philadelphia: Lippincott Williams & Wilkins.
Guyton A., & Hall, J. (2006), Contraction of Skeletal Muscle. In Textbook of Medical Physiology(11th ed., p.78), Philadelphia: Elsevier Saunders.