Maintenance of a Healthy PH in Human Body - Report Example

Discuss how the body keeps blood pH within the healthy range Introduction Maintenance of a healthy pH is vital for the human body. The normal body pHranges from 7.35 to 7.45 where deviations from the normal range can prove fatal as many of the enzyme controlled reactions occurring within our body are sensitive to pH changes (Jones at al. 2007, 47). A great portion of our human body comprises of proteins including enzymes and hormones, which are globular proteins. Such chemicals, particularly enzymes are pH and temperature sensitive where they work optimally at a particular pH and temperature. Any deviation from the required pH causes a distortion in the tertiary structure of proteins and consequently causes the denaturation of enzymes, thereby affecting the functioning of the human body. Not only is it necessary to maintain pH within our blood but it is also important to regulate the intracellular pH levels, especially as required by the brain. Several physiological and pathological processes in our body result in pH changes and our body mechanisms work to regulate such changes. Because pH measures the concentration of hydrogen ions, activities such as food intake, excessive exercise, and alcoholism causes a change in the blood pH levels. This essay will discuss how the body maintains a normal blood pH level. Mechanism for blood pH regulation Homeostasis is a process within the body involved in the maintenance of a stable internal environment. Part of the homeostasis process is the regulation of blood pH levels and the acid base concentration through buffers, chemo sensors present in the brain and the blood circulation, kidneys, and lungs. These components form the essential acid-base component of the body. The buffers include chemicals such as bicarbonate, proteins, phosphates, and so on. Bicarbonate is an important buffer due to its chemical reaction where it breaks down into its constituent components. It can either form carbon dioxide and water or form hydrogen ions (H+) and bicarbonate ions (HCO3-) (Seifter, Sloane and Ratner 2005, 392; Rhoades and Bell 2009, 458). Any acid-base change within the body is countered by the buffering system without having to remove the acids or bases from the body (Johnson and Byrne 2003, 296). Lungs also act as a secondary line of defense with the renal compensation working to act as a late response. Physiological sources of acid Two main sources of acid exist within our body. The first includes volatile and gaseous sources such as carbon dioxide, which is produced as an end product in metabolic reactions of dietary carbohydrates and fats. All aerobic cells within our body undergo respiration and metabolism, during which they produce carbon dioxide. An increased amount of carbon dioxide increases the concentration of hydrogen ions (H+) within the body thereby lowering the blood pH levels. The non-volatile sources of acid are created through the metabolism of amino acids. The end products of amino acid metabolism mainly includes hydrochloric acid (HCl) and sulfuric acid (H2SO4), which increases the concentration of hydrogen ions thereby shifting the carbonic acid equation towards carbon dioxide and lowering the bicarbonate levels (Seifter, Sloane and Ratner 2005, 393). Changes in the systemic pH also control the rate of endogenous acid production, which is both rapid and reversible. Keto acids and lacto acids are endogenously produced in the body are products of metabolism. Lactic acid is an important source of energy during exercise while keto acids serve as sources of energy during the conditions of fasting or starvation. A low pH inhibits the production of glycolytic metabolism producing lactic acids and a high pH stimulates the process (Hood and Tannen 1998). Therefore, there is a need for a pH regulation system in the form of buffers. Blood pH buffer systems Major chemical pH buffers in the body are in the form of acid-base conjugates and regulate the pH. In the ECF, important buffers are in the form of bicarbonates or carbon dioxide, inorganic phosphate, plasma proteins and in the ICF the important chemical buffers include cell proteins such as hemoglobin, organic phosphates, and bicarbonates or carbon dioxide. Bones also play a central role in the buffering system as they contain mineral phosphates and carbonates for the regulation of blood pH (Rhoades and Bell 2009, 455). Findings from research have shown that during both, acute and chronic, conditions of pH aberrations, the buffering system in the bones are activated. A low pH level leads to a loss of calcium ions from the bones and buffering of hydrogen ions, thereby bringing the pH to normal levels. Release of calcium ions is associated with the generation of an alkaline environment thereby increasing the pH levels. The response of bone buffers is more active during metabolic acidosis as compared to respiratory acidosis. Bones are key reservoirs of carbon dioxide in the form of carbonates and during metabolic acidosis it leads to active release of carbonates into the blood (Green and Kleeman 1991). Beyond the bones, the kidneys also act as important buffer systems for the regulation of blood pH levels. Renal compensation of metabolic acidosis Kidneys perform a major role in the regulation of acid-base balance by controlling the amount of bicarbonate concentration within the body. Kidneys reabsorb the bicarbonate to prevent its depletion in cases such as metabolic acidosis. The kidneys also excrete large amounts of bicarbonates in situations of metabolic alkalosis. The proximal convoluted tubules in the kidneys are the principle sites of the reabsorption of most of the bicarbonates. However, the bicarbonate is not directly reabsorbed, it is first combined with hydrogen ions to form carbonic acid which is then acted upon by the carbonic anhydrase enzyme that are present in the brush border of the proximal cells (Lee 2009, 180). It is converted to carbon dioxide which then diffuses across the cell membrane and into the cell where it forms carbonic acid and bicarbonate ions again. The bicarbonate ions are then reabsorbed into the blood capillaries. Respiratory compensation of metabolic acidosis Lungs maintain the blood pH levels mainly through the regulation of PaCO2. After the veins return the blood from the tissues to the heart, the pulmonary artery takes the blood to the lungs where the carbon dioxide is diffused from the capillaries to the alveoli thereby getting exhaled outside (Lee 2009, 180). The rate at which carbon dioxide is excreted from the body coincides with the rate of ventilation. Chemo receptors in the medulla of the brain as well as the arteries are highly sensitive to the blood PaCO2 levels and respond by increasing or decreasing ventilation. Increased ventilation decreases the carbon dioxide while reduced ventilation increases the carbon dioxide levels in the blood. Lungs therefore respond quickly to changes in the blood pH levels and act by adjusting the ventilation rate. The rate of respiration is complemented by an increase in ventilation. Besides this, other processes occurring within the body are also important for the maintenance of a constant body environment and most importantly, a normal blood pH level. ECF Potassium Changes Maintenance of a normal extracellular potassium range is important for various normal body functions, most importantly the electrical activity of the heart muscles. Metabolic acidosis leads to shifting of potassium from the intracellular compartment to the outside of cell leading to hyperkalemia. On the other hand, in alkalosis, there is a net shift of potassium ions from the ECF to the inside of the cell leading to hypokalemia. Most of the exchange takes place through the K-H exchange pump present on the cell membrane of several cells. In acidosis, an increased number of hydrogen ions (H+) are shifted into the cell with a net shift potassium outwards and the opposite is the case with alkalemia (Aronson and Giebisch 2011). There is no change in the ICF voltage of the cells in patients with respiratory acid-base disturbances because at such conditions, the movement of sodium ions (Na+) and chloride ions (Cl-) across the cells is minimal and therefore, no net effect on potassium is observed (Halperin, Goldstein and Stark 1994). Acid-base imbalances Metabolic acidosis is characterized by decreased plasma pH, that is, less than 7.35, and decreased plasma bicarbonate levels (Porth and Hannon 2010). Metabolic alkalosis is characterized by an increase in plasma pH and an increase in plasma bicarbonates. It can be caused by an increased intake of bicarbonate, increased loss of hydrogen ions, or retention of bicarbonates or retraction of alkalosis (Porth and Hannon 2010, 786). Respiratory acidosis is characterized by a rapid increase in arterial PCO2, a minimal decrease in plasma bicarbonate and an increase in plasma pH. It can be caused by a depression in respiratory center or any lung disease, such as emphysema or pneumonia, airway obstruction or disorder of chest wall or respiratory muscles leading to hypoventilation and it can also be a result of long-term breathing in air that contains high levels of carbon dioxide. Respiratory alkalosis is also known as hypocapnia because of fall in arterial PCO2, a minimal rise in plasma bicarbonates and rise in plasma pH. Causes of respiratory alkalosis include conditions which lead to hyperventilation such as anxiety, hypoxia, lung disease, stimulation of respiratory centers, salicylate toxicity and fever (Porth and Hannon 2010, 787-789). Conclusion Regulation of pH in blood is governed by several mechanisms which are activated at various stages in time or based on the severity of deviations from normal ranges. All the body functions and the protein structures are sensitive to changes in pH levels and hence, body systems are activated as soon as deviations are detected. Chemical buffer systems are composed of proteins, phosphates, and bicarbonates, and are the first line of defense in case of pH aberrations. Lungs are also seminal components of the system in maintaining the blood pH levels assisted by the detection carried out by chemo receptors in the brain. Since they are sensitive to changes in blood PCO2 levels, they can quickly respond by adjusting the ventilation. Through excretion or reabsorption of bicarbonates, the kidneys also help in the regulation of blood pH. Bones also buffer changes in pH through the carbonate reserves they hold. References Aronson, P. and Giebisch, G. (2011). Effects of pH on potassium: new explanations for old observations. Journal of the American Society of Nephrology, 22(11), pp.1981--1989. Hood, V. and Tannen, R. (1998). Protection of acid--base balance by pH regulation of acid production. New England Journal of Medicine, 339(12), pp.819--826. Green, J. and Kleeman, C. (1991). Role of bone in regulation of systemic acid-base balance. Kidney International, 39(1), pp.9--26. Halperin, M., Goldstein, M. and Stark, J. (1994). Fluid, electrolyte and acid-base physiology: a problem-based approach. Critical Care Nursing Quarterly, 17(3), pp.88--89. Johnson, L. and Byrne, J. (2003). Essential medical physiology. 1st ed. Amsterdam: Elsevier Academic Press. Jones, M., Frosbery, R., Taylor, D. and Gregory, J. (2007). 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