Systems which maintain acid base balance

It therefore improves the acidosis initially but then worsens it if respiratory compensations are not effective RCUK, In acid-base balance other factors are involved in the homeostatic control of the vital components.

These have their own homeostatic mechanisms, which should be considered when looking at the patient holistically. They include:. Haemoglobin - The amount of haemoglobin in the blood affects its oxygen-carrying capacity. This may be too long in the acute setting Proehl, Haemoglobin also acts as a buffer to hydrogen ions in red blood cells, so in acidosis in low haemoglobin states the cells are less able to buffer the acidic effect as efficiently Woodrow, Temperature - Temperature will impact on the amount of oxygen dissociation from oxyhaemoglobin molecules in the circulating blood, and so this should also be considered and corrected where possible Adam and Osborne, Blood pressure - The cardiovascular system should be sufficiently strong to circulate adequate volumes of blood around the body and if there is heart failure for example low cardiac output this will impact on the delivery of oxygen to tissues and the clearance of waste products such as carbon dioxide Proehl, ; Smith, This might be in the form of fluid management for example blood cells or crystalloid , drug therapy for example inotropic support or mechanical support for example a pacemaker or intra-aortic balloon pump Docherty, a; Smith, Sign in or Register a new account to join the discussion.

You are here: Haematology. These weak acids and bases exist in pairs that are in balance under normal pH conditions. The pH buffer systems work chemically to minimize changes in the pH of a solution by adjusting the proportion of acid and base. The most important pH buffer system in the blood involves carbonic acid a weak acid formed from the carbon dioxide dissolved in blood and bicarbonate ions the corresponding weak base.

Acidosis Acidosis Acidosis is caused by an overproduction of acid that builds up in the blood or an excessive loss of bicarbonate from the blood metabolic acidosis or by a buildup of carbon dioxide in the blood Alkalosis Alkalosis Alkalosis is excessive blood alkalinity caused by an overabundance of bicarbonate in the blood or a loss of acid from the blood metabolic alkalosis , or by a low level of carbon dioxide in Acidosis and alkalosis are not diseases but rather are the result of a wide variety of disorders.

The presence of acidosis or alkalosis provides an important clue to doctors that a serious problem exists.

Metabolic acidosis and metabolic alkalosis are caused by an imbalance in the production of acids or bases and their excretion by the kidneys. Respiratory acidosis and respiratory alkalosis are caused by changes in carbon dioxide exhalation due to lung or breathing disorders. Each acid-base disturbance provokes automatic compensatory mechanisms that push the blood pH back toward normal. In general, the respiratory system compensates for metabolic disturbances while metabolic mechanisms compensate for respiratory disturbances.

At first, the compensatory mechanisms may restore the pH close to normal. Thus, if the blood pH has changed significantly, it means that the body's ability to compensate is failing. In such cases, doctors urgently search for and treat the underlying cause of the acid-base disturbance.

A buffer is a chemical system that prevents a radical change in fluid pH by dampening the change in hydrogen ion concentrations in the case of excess acid or base. Most commonly, the substance that absorbs the ions is either a weak acid, which takes up hydroxyl ions, or a weak base, which takes up hydrogen ions.

The buffer systems in the human body are extremely efficient, and different systems work at different rates. It takes only seconds for the chemical buffers in the blood to make adjustments to pH. The respiratory tract can adjust the blood pH upward in minutes by exhaling CO 2 from the body. The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers. The kidneys help control acid-base balance by excreting hydrogen ions and generating bicarbonate that helps maintain blood plasma pH within a normal range.

Protein buffer systems work predominantly inside cells. Nearly all proteins can function as buffers. Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups.

The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers. Buffering by proteins accounts for two-thirds of the buffering power of the blood and most of the buffering within cells. Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell. During the conversion of CO 2 into bicarbonate, hydrogen ions liberated in the reaction are buffered by hemoglobin, which is reduced by the dissociation of oxygen.

This buffering helps maintain normal pH. The process is reversed in the pulmonary capillaries to re-form CO 2 , which then can diffuse into the air sacs to be exhaled into the atmosphere. This process is discussed in detail in the chapter on the respiratory system.

Acids and bases are still present, but they hold onto the ions. The bicarbonate-carbonic acid buffer works in a fashion similar to phosphate buffers. The bicarbonate is regulated in the blood by sodium, as are the phosphate ions. When carbonic acid comes into contact with a strong base, such as NaOH, bicarbonate and water are formed. As with the phosphate buffer, a weak acid or weak base captures the free ions, and a significant change in pH is prevented. Bicarbonate ions and carbonic acid are present in the blood in a ratio if the blood pH is within the normal range.

With 20 times more bicarbonate than carbonic acid, this capture system is most efficient at buffering changes that would make the blood more acidic. Carbonic acid levels in the blood are controlled by the expiration of CO 2 through the lungs. For instance, uncontrolled diabetes results in highly acidic urine. If the diabetes remains uncontrolled, the kidneys could become over-stressed and malfunction, which could lead to coma or death.

Within the human body, fluids such as blood must be maintained within the narrow range of 7. Outside that range, pH becomes incompatible with life; proteins are denatured and digested, enzymes lose their ability to function, and the body is unable to sustain itself.

To maintain this narrow range of pH the body has a powerful buffering system. Acid—base imbalances that overcome this system are compensated in the short term by changing the rate of ventilation. The kidneys are slower to compensate than the lungs, but renal physiology has several powerful mechanisms to control pH by the excretion of excess acid or base. The major, homeostatic control point for maintaining a stable pH balance is renal excretion. In response to acidosis, the tubular cells reabsorb more bicarbonate from the tubular fluid, and the collecting duct cells secrete more hydrogen and generate more bicarbonate, and ammoniagenesis leads to an increase in the formation of the NH 3 buffer.

In response to alkalosis, the kidneys may excrete more bicarbonate by decreasing hydrogen ion secretion from the tubular epithelial cells, and lowering the rates of glutamine metabolism and ammonium excretion.

Privacy Policy. Skip to main content. Body Fluids and Acid-Base Balance. Search for:. Acid-Base Balance. Learning Objectives Explain the composition of buffer solutions and how they maintain a steady pH. Key Terms alkaline : having a pH greater than 7; basic acidic : having a pH less than 7 buffer : a solution composed of a weak acid and its conjugate base that can be used to stabilize the pH of a solution.

Learning Objectives Distinguish between buffer solutions, ventilation, and renal function as buffer systems to control acid—base balance. Buffer solutions keep the pH constant in a wide variety of chemical actions.

A buffer solution is a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid.