Since ectothermic animals cannot regulate their own body temperatures, their metabolism is affected by the external temperature. Metabolism has two metabolic pathways. The first is the catabolic pathway, which breaks down complex compounds, such as glucose and proteins, into simple compounds. This makes energy available for the working of the cell. The second pathway is the anabolic pathway, which builds complex compounds needed by the body, such as protein for muscle, from these simple compounds.
Because chemical reactions are unpredictable -- they may not produce the right compounds, or the required amount -- cells need enzymes to regulate metabolic activity. Enzymes bring the right chemicals together and speed up chemical reactions. Enzymes are therefore catalysts of chemical reactions. Only a small amount of the energy obtained from food becomes energy that powers cells. The rest is lost as heat, which is a byproduct of chemical reactions. This heat escapes the bodies of humans and other organisms and is what causes a room full of people to get uncomfortably hot.
Heat generated by metabolism plays an important role in keeping the bodies of endothermic animals warm. Endotherms, primarily birds and mammals, are animals that are able to regulate their own body temperature using the energy generated by metabolism. With pyruvate accumulation, lactic acid production is also increased. This further inhibits anaerobic respiration, inducing fatigue.
Lactic acid can be converted back to pyruvate in well-oxygenated muscle cells; however, during exercise the focus in on maintaining muscle activity. Lactic acid is transported to the liver where it can be stored prior to conversion to glucose in the presence of oxygen via the Cori Cycle. The amount of oxygen required to restore the lactic acid balance is often referred to as the oxygen debt.
With extensive exercise, the osmotically active molecules outside of the muscle are lost through sweating. In extreme cases, this can lead to painful, extended maintenance of muscle contraction or cramp. Nerves are responsible for controlling the contraction of muscles, determining the number, sequence, and force of muscular contractions. Most movements require a force far below what a muscle could potentially generate, and barring disease nervous fatigue is seldom an issue. However, loss of desire to exercise in the face of increasing muscle soreness, respiration, and heart rate can have a powerful negative impact on muscle activity.
Depletion of required substrates such as ATP or glycogen within a muscle result in fatigue as the muscle is not able to generate energy to power contractions.
With sufficient training, the metabolic capacity of a muscle can change, delaying the onset of muscle fatigue. Muscle specified for high-intensity anaerobic exercise will synthesise more glycolytic enzymes, whereas muscle for long endurance aerobic exercise will develop more capillaries and mitochondria.
Additionally, with exercise, improvements to the circulatory and respiratory systems can facilitate better delivery of oxygen and glucose to the muscle. Muscle fibers shrink or are lost and surrounding connective tissue hardens, making muscle contraction slower and more difficult.
Exercise throughout life can help reduce the impact of aging by maintaining a healthy oxygen supply to the muscle. Privacy Policy. Skip to main content. Muscular System. Search for:. Muscle Metabolism. Muscle Metabolism Muscle contraction occurs via metabolism of adenosine triphosphate ATP derived primarily from the simple sugar glucose. The environment provides this element through various ways including rain, rivers, lakes and oceans.
Human beings use water for drinking, washing, irrigation and power generation. Shelter: some of the materials used in construction include sand, stones and trees. The environment has an abundance of these raw materials and that is why human beings are able to build decent shelters.
Clothing: without clothing, human beings would find it difficult to cope with the harsh elements of the climate. The environment provides raw materials, such as silk and cotton, which are all used in manufacture of clothing products.
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