Acid Base Equilibrium

Homoeostasis or homœostasis (from Greek: ὅ μοιος, "hómoios", "similar", [1] and στάσις, stásis, "standing still" [2] ), is the property of a system in which variables are regulated so that internal conditions remain stable and relatively constantGreek [1] [2] Examples of homeostasis include the regulation of temperature and the balance between acidity and alkalinity (pH).pH It is a process that maintains the stability of the human body's internal environment in response to changes in external conditions.

Extracellular fluid (ECF) or extracellular fluid volume (ECFV) usually denotes all body fluid outside of cells. The remainder is called intracellular fluidbody fluidintracellular fluid Extracellular Fluid, in conjunction with intracellular fluid, helps control the movement of water and electrolytes throughout the body. In order to maintain osmotic balance, the extracellular compartments of a mammal's body must be able to excrete and absorb water to and from the environment. Inorganic ions must also be exchanged between ECF and the external environment to maintain homeostasis

Paramater of CES should be maintained in homeostic state are :  Nutrient  O2 dan CO2  Metabolite  pH  Water, salt and electrolyte  Temperature  Volume and pressure

All cells contain an intracellular fluid whose pH value is known as the intracellular pH (pHi). The pHi plays a critical role in the function of the cell, and close regulation is required for cells to survive.

Acid Base Physiology Definition: pH is defined as potential of H + Ion concentration in body fluid. The amount of H + ion concentration is so low in the body hence it is expressed as –ve logarithm to base of the H + ion concentration in mEq/lit. pH = log 1/ [H + ] = - log [H + ]

The Acid-Base Balance Balance of H conc. in Extra Cellular Fluid ----  To Achieve Homeostasis Balance Between : The H Intake or Production The H Removal

NORMAL VALUE Arterial blood = 7.35 – 7.45 The normal extracellular pH is 7.4 +/-.1 Intracellular pH is around 6.8 due to acid production

Acid – Base Imbalance Acidosis = Decrease in arterial PH ( <7.35 ) Due to excess H+ Alkalosis = Elevation in Arterial PH ( >7.45) Due to excess base.

pH and H + ion concentration pH H + ion in nmol/lit Note : one point drop in pH results in a ten fold decrease in H + ion conc.

Scale of pH measurement The pH scale is between 0 – 14. Zero onwards below 7 is acidic. After 7 upto 14 the solution is alkaline. At 7 (neutral e.g. water) where the amount of H+ and Hydroxyl ion are equal at 23 o

Since pH is inversely related to H+ ion conc. so a low pH corresponds to high H+ ion conc. (Acidic) and a high pH corresponds to low H+ ion conc. (Alkaline) Acidic Neutral Alkaline

The Negative logarithmic relationship between [H + ] and pH

A very tight control is needed for normal metabolic functions. eg. Enzymatic activity, blood clotting and neuromuscular activity. Hydrogen ions are the toxic end product of metabolism and they adversely affect all physical and biochemical cellular process in our body.

21.5: Acid-Base Balance 15 Electrolytes that ionize in water and release hydrogen ions are acids Substances that combine with hydrogen ions are bases Acid-base balance entails regulation of the hydrogen ion concentrations of body fluids This is important because slight changes in hydrogen ion concentrations can alter the rates of enzyme-controlled metabolic reactions, shift the distribution of other ions, or modify hormone actions

Acid Molecules containing H atoms that can release (donate) H ions in solutions.  Example, HCL. Strong acids : - Completely dissociate : (HCL, H 2 SO 4 ) Weak acid : - Partially dissociate : ( H 2 CO 3 )

Base An Ion that accept a H ion. An example of a base is the Bicarbonate ( HCO3 ).

Strengths of Acids and Bases 18 Acids: Strong acids ionize more completely and release more H + Weak acids ionize less completely and release fewer H + Bases: Strong bases ionize more completely and release more OH - Weak bases ionize less completely and release fewer OH -

Buffers Substances that Neutralize acids or bases. Chemical Reactions which Reduce the effect of adding acid or base to a solution PH.

How the body defends against fluctuations in PH Three Systems in the body : 1) Buffers in blood. 2) Respiration through the lungs. 3) Excretion by the kidney.

Blood Buffer These buffer systems serve as a first line of defense against changes in the acid-base balance : - HCO3(Regulated by Renal and Respiratory). - Protein - Phosphate - Hemoglobin

Protein and hemoglobin Acidic and Basic Amino acid in plasma and cell protein act as buffers. Hemoglobin is an important buffer, can’t be regulated physiological.

Phosphate & Intracellular Buffers Both Intra and Extra cellular phosphate act as a buffer. But its role is minor compared to Hb or HCO3. Intracellular buffers are needed because H doesn’t cross Plasma Membrane. Intracellular PH is more acidic. (7.2)

Sources of Hydrogen Ions 24 Aerobic respiration of glucose Anaerobic respiration of glucose Incomplete oxidation of fatty acids Oxidation of sulfur-containing amino acids Hydrolysis of phosphoproteins and nucleic acids Carbonic acid Lactic acid Acidic ketone bodies Sulfuric acid Phosphoric acid H + Internal environment Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Medical studies report that a pH that is imbalanced can be correlated to almost all health conditions, including heart disease, arthritis and cancer Acidic blood (having low pH levels) can create cause toxic and acidic waste (acidosis). This is a mostly unknown and dangerously destructive circumstance because it can lead to chronic diseases such as heart disease and cancer. Serious health problems such as low energy, unwanted weight gain, poor athletic performance and accelerated aging, inflammation and auto-immune disorders can be potentially increased as well.

Regulation of Hydrogen Ion Concentration 26 Either an acid shift or an alkaline (basic) shift in the body fluids could threaten the internal environment Normal metabolic reactions generally produce more acid than base These reactions include cellular metabolism of glucose, fatty acids, and amino acids Maintenance of acid-base balance usually eliminates acids in one of three ways: Acid-base buffer systems Respiratory excretion of carbon dioxide Renal excretion of hydrogen ions

Acid-Base Buffer Systems 27 Bicarbonate buffer system The bicarbonate ion converts a strong acid to a weak acid Carbonic acid converts a strong base to a weak base H + + HCO 3 -  H 2 CO 3  H + + HCO 3 - Phosphate buffer system The monohydrogen phosphate ion converts a strong acid to a weak acid The dihydrogen phosphate ion converts a strong base to a weak base H + + HPO 4 -2  H 2 PO 4 -  H + + HPO 4 -2 Protein buffer system NH3 + group releases a hydrogen ion in the presence of excess base COO - group accepts a hydrogen ion in the presence of excess acid

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Respiratory Secretion of Carbon Dioxide 29 The respiratory center in the brainstem helps regulate hydrogen ion concentrations in the body fluids by controlling the rate and depth of breathing If body cells increase their production of CO 2 … More CO 2 is eliminated through lungs Rate and depth of breathing increase Respiratory center is stimulated Cells increase production of CO 2 CO 2 reacts with H 2 O to produce H 2 CO 3 H 2 CO 3 releases H + Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Renal Excretion of Hydrogen Ions 30 Nephrons help regulate the hydrogen ion concentration of body fluids by excreting hydrogen ions in the urine High intake of proteins Increased concentration of H + in urine Increased secretion of H + into fluid of renal tubules Increased concentration of H + in body fluids Increased metabolism of amino acids Increased formation of sulfuric acid and phosphoric acid Concentration of H + in body fluids returns toward normal.

Time Course of Hydrogen Ion Regulation 31 Various regulators of hydrogen ion concentration operate at different rates Acid-base (chemical buffers) function rapidly Respiratory and renal (physiological buffers) mechanisms function more slowly Phosphate buffer system Protein buffer system First line of defense against pH shift Second line of defense against pH shift Chemical buffer system Physiological buffers Bicarbonate buffer system Respiratory mechanism (CO 2 excretion) Renal mechanism (H + excretion ) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21.6: Acid-Base Imbalances 32 Chemical and physiological buffer systems ordinarily maintain the hydrogen ion concentration of body fluids within very narrow pH ranges Abnormal conditions may disturb the acid-base balance 7.35 Survival range Normal pH range pH scale AcidosisAlkalosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Acidosis & Alkalosis 33 Acidosis results from the accumulation of acids or loss of bases, both of which cause abnormal increases in the hydrogen ion concentrations of body fluids Alkalosis results from a loss of acids or an accumulation of bases accompanied by a decrease in hydrogen ion concentrations pH rises pH drops Increased concentration of H + pH scale 7.4 Acidosis Alkalosis Decreased concentration of H + Accumulation of acids Loss of bases Loss of acids Accumulation of bases Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Acidosis 34 Two major types of acidosis are respiratory acidosis and metabolic acidosis Accumulation of CO 2 Respiratory acidosis Decreased rate and depth of breathing Obstruction of air passages Decreased gas exchange Accumulation of nonrespiratory acids Metabolic acidosis Excessive loss of bases Kidney failure to excrete acids Excessive production of acidic ketones as in diabetes mellitus Prolonged diarrhea with loss of alkaline intestinal secretions Prolonged vomiting with loss of intestinal secretions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Alkalosis 35 Respiratory alkalosis develops as a result of hyperventilation Metabolic alkalosis results from a great loss of hydrogen ions or from a gain in bases, both accompanied by a rise in the pH of blood Excessive loss of CO 2 Hyperventilatio n Decrease in concentration of H 2 CO 3 Decrease in concentration of H + Respiratory alkalosis Anxiety Fever Poisoning High altitude Loss of acids Net increase in alkaline substances Metabolic alkalosis Gastric drainage Vomiting with loss of gastric secretions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

REASONS FOR METABOLIC ACIDOSIS AND ALKALOSIS

CAUSES OF RESPIRATORY ACIDOSIS AND ALKALOSIS

The body response to acid-base IMBALANCE is called Compensation If the body is bruoght to the normal limits then, It is Complete If the Range is still outside the normal then, It is Partial

Compensation -If underlying problem is metabolic : Hyperventilation and Hypoventilation mechanisms will help through Respiratory Compensation. -If the problem is Respiratory, Renal mechanisms, then Renal mechanisms will help through Metabolic Compensation.

COMPENSATION IN PRIMARY METABOLIC DISORDERS

RENAL COMPENSATION IN PRIMARY RESPIRATORY ACIDOSIS

-Principal effect of acidosis is Depression of the CNS through the decrease in synaptic transmission. - Generalized Weakness. - Dearranged CNS is the greatest thread. - severe acidosis causes : 1- Disorientation 2- Coma 3- Death Acidosis

Alkalosis -Causes over excitability of the central and peripheral nervous systems. -Numbness - Light headedness It can cause : - nervousness. - muscle spasms or tetany. - convulsions - loss of consciousness - death.