Download - Acid Base Equilibrium. Homoeostasis or homœostasis (from Greek: ὅ μοιος, "hómoios", "similar", [1] and στάσις, stásis, "standing still" [2] ), is the.

Transcript

Acid Base Equilibrium

Homoeostasis or homœostasis (from Greek: ὅμοιος, "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 constant

Examples of homeostasis include the regulation of temperature and the balance between acidity and alkalinity (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 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 – 7.45The normal extracellular pH is 7.4 +/- .1Intracellular 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

pH6.07.08.09.0

H+ ion in nmol/lit1000100101.0

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 23o

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

14

0 7

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 Balance15

• 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 , H2SO4 )Weak acid : - Partially dissociate : ( H2CO3)

Base

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

Strengths of Acids and Bases18

• 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 Ions24

Aerobicrespirationof glucose

Anaerobicrespirationof glucose

Incompleteoxidation offatty acids

Oxidation ofsulfur-containingamino acids

Hydrolysis ofphosphoproteinsand nucleic acids

Carbonicacid

Lacticacid

Acidic ketonebodies

Sulfuricacid

Phosphoricacid

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 Concentration26

• 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 Systems27

• 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+ + HCO3- H2CO3 H+ + HCO3

-

• 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+ + HPO4

-2 H2PO4- H+ + HPO4

-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

28

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 CO2…

More CO2 is eliminated through lungs

Rate and depth of breathing increase

Respiratory center is stimulated

Cells increase production of CO2

CO2 reacts with H2O to produce H2CO3

H2CO3 releases H+

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Renal Excretion of Hydrogen Ions30

• Nephrons help regulate the hydrogen ion concentration of body fluids by excreting hydrogen ions in the urine

High intake of proteins

Increased concentrationof H+ in urine

Increased secretionof H+ into fluid ofrenal tubules

Increased concentrationof H+ in body fluids

Increased metabolismof amino acids

Increased formationof sulfuric acid andphosphoric acid

Concentration of H+

in body fluids returnstoward 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

Phosphatebuffer system

Proteinbuffer system

First line of defenseagainst pH shift

Second line ofdefense againstpH shift

Chemicalbuffer system

Physiologicalbuffers

Bicarbonatebuffer system

Respiratorymechanism(CO2 excretion)

Renalmechanism(H+ excretion)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21.6: Acid-Base Imbalances32

• 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

7.45 8.07.06.8 7.8

Acidosis Alkalosis

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Acidosis & Alkalosis33

• 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+

Accumulationof acids

Loss ofbases

Loss ofacids

Accumulationof 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 CO2

Respiratoryacidosis

Decreased rateand depth ofbreathing

Obstruction ofair passages

Decreasedgas exchange Accumulation of nonrespiratory acids

Metabolic acidosis

Excessive loss of bases

Kidney failureto excrete acids

Excessive production of acidicketones as in diabetes mellitus

Prolonged diarrheawith loss of alkalineintestinal secretions

Prolonged vomitingwith loss of intestinalsecretions

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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 CO2

Hyperventilation

Decrease in concentration of H2CO3

Decrease in concentration of H+

Respiratory alkalosis

• Anxiety

• Fever

• Poisoning

• High altitude

Loss of acids

Net increase in alkaline substances

Metabolic alkalosis

Gastricdrainage

Vomiting with lossof 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 IMBALANCEis 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 .