advanced physiology (part 3, acid-base balance) by: a. riasi (phd in animal nutrition &...
TRANSCRIPT
Advanced PhysiologyAdvanced Physiology(part 3, Acid-base balance)(part 3, Acid-base balance)
By: A. Riasi (PhD in Animal Nutrition & Physiology)Isfahan University of Technology (IUT)
فیزیولوژی تکمیلی
Introduction
Three aspects of the ECF and ICF that are crucial to the
whole animal and to its individual cells:
The osmotic balance
Total fluid volume of the body
Acid –base status
Introduction
The term of acid-base balance refers to the precise regulation
of free hydrogen ion (H+) and hydronium ion (OH-)
concentration in the body fluids.
Acids are a special group of hydrogen-containing substances.
A strong acid has a greater tendency to dissociated in solution
than does a weak acid.
Acid-base balance in body fluids
�َAdapted from Animal Physiology by Sherwood et al. 2005
Acid-base balance in body fluids
The normal pH of arterial and venous blood
Acidosis exists whenever the blood pH falls below 7.35
Alkalosis occurs when the blood pH is above 7.45
Death can occur if arterial pH falls outside of the range of 6.8-8.0
Acid-base balance in body fluids
�َAdapted from Animal Physiology by Sherwood et al. 2005
Fluctuations in hydrogen ion concentration have profound
effect on body chemistry.
Even small changes in [H+] have dramatic effect on proteins.
The most prominent whole body consequences of fluctuations in
[H+] are changes in excitability of nerves and muscle cells.
Acid-base balance in body fluids
Hydrogen ions are continually being added to body fluids
Metabolic activities are main source for H+ in the body fluids
Normally, H+ is continually being added to the body fluids by:
Carbonic acid formation
Inorganic acid produced during the breakdown of nutrients
Organic acid resulting from intermediary metabolism
Acid-base balance in body fluids
Acid-base balance in body fluids
CO2 + H2O H2CO3 H+ + HCO3-
CO2 + OH- HCO3-CA
H2O H+ + OH-
Sulfuric acid and phosphoric acid are produced in the body.
Fatty acids and lactic acid that are produced during
intermediary metabolism partially dissociate to yield free H+.
In certain disease additional acids may be produced.
Acid-base balance in body fluids
Three line of defense against changes in [H+]:
Chemical buffer systems
Respiratory mechanisms of pH control
Excretory mechanisms of pH control
Acid-base balance in body fluids
There are four buffer system in the vertebrate body:
CO2-HCO3- buffer system
The peptide and protein buffer system
The hemoglobin buffer system
The phosphate buffer system
pH Regulation: Buffers
The Co2-HCO3- buffer system in the ECF.
pH Regulation: Buffers
�َAdapted from Animal Physiology by Sherwood et al. 2005
The most plentiful buffers on the ICF are the cell proteins.
The most important buffering amino acid is histidine.
pH Regulation: Buffers
Hemoglobin (Hb) in erythrocytes buffers the H+ generated.
The phosphate buffer system consists of an acid phosphate
slat (NaH2PO4) and a basic phosphate salt (Na2HPO4).
The phosphate system serve as an excellent urinary buffer.
The respiratory system plays an important role in acid-base
balance through its ability to alter ventilation
pH Regulation: Respiration
The excretory organs are the third line of defense against
changes in [H+] in body fluids.
In mammals, the kidneys are the most potent acid-base
regulatory mechanism.
The kidneys can remove of H+ from any source
The kidneys can variably conserve or eliminate HCO3-
pH Regulation: Excretion
The kidneys control the pH of the body fluids by adjusting
three interrelated factors:
H+ excretion
H2CO3- excretion
Ammonia secretion
pH Regulation: Excretion
Hydrogen ion excretion by the kidneys
The kidneys eliminate H+ derived from sulfuric, phosphoric,
lactic, and other acids.
pH Regulation: Excretion
pH Regulation: Excretion
�َAdapted from Animal Physiology by Sherwood et al. 2005
The H+ secretary process begins in the tubular cells with
CO2 that has come from three sources:
The CO2 diffused from plasma
The CO2 diffused from the tubular fluid
CO2 that has been metabolically produced within the tubular
cells.
pH Regulation: Excretion
The kidneys adjust H+ excretion to compensate for changes
in both carbonic and noncarbonic acids.
The kidneys regulate plasma [HCO3-] by two mechanisms:
Variable reabsorption of the filtered HCO3- back to the plasma.
Variable addition of new HCO3- to the plasma.
pH Regulation: Excretion
pH Regulation: Excretion
�َAdapted from Animal Physiology by Sherwood et al. 2005
pH Regulation: Excretion
�َAdapted from Animal Physiology by Sherwood et al. 2005