acid base equilibrium. homoeostasis or homœostasis (from greek: ὅ μοιος,...
TRANSCRIPT
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
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)
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
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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
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+
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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)
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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
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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
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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
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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
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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 .
-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