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Functions of the constituents of body fluids

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Johanne brolly

on 21 January 2016

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Transcript of Functions of the constituents of body fluids

Acid-Base homeostasis involves chemical and physiologic processes responsible for the maintenance of the acidity of body fluids at levels that allow optimal function of the whole individual
What are they?
chemical processes
represent the first line of defense to an acid or base load and include the
extracellular and intracellular buffers

physiologic processes
modulate acid-base composition by changes in cellular metabolism and by adaptive responses by the
and fixed acids by the
Activity 1
Identify on the body where you think most of the acid-base homestasis happens.

When you have been given the answers, sick them on the right place.
Acid - Base balance is primarily concerned with two ions:

Hydrogen (H+)

Bicarbonate (HCO3- )

(Changes in hydrogen and bicarbonate concentrations in body fluids are common in disease processes)

Acid-base homeostasis:
part of human homeostasis concerning the proper balance between acids and bases

As humans are very sensitive to the pH level within it, strong mechanisms exist to maintain it.

If the pH level shifts outside the acceptable range of pH,
proteins are denatured and digested,
enzymes lose their ability to function, and
death may occur.

Functions of the constituents of body fluids
What do you already know about maintaining a constant pH in the body?
shout out your answers and we will jot down on the board

Acid-Base Regulation
Maintenance of an acceptable pH range in the extracellular fluids is accomplished by three mechanisms:
Chemical Buffers
React very rapidly(less than a second)
Respiratory Regulation
Reacts rapidly (seconds to minutes)
Renal Regulation
Reacts slowly (minutes to hours)

All cells in the body continually exchange chemicals (e.g.,nutrients, waste products, and ions) with the external fluid surrounding them

This external fluid, in turn, exchanges chemicals with the blood being pumped throughout the body.

This usually occurs through diffusion through membrane channels, due to a concentration gradient associated with the contents of the fluids.

Therefore, the chemical composition of the blood (and therefore of the external fluid) is extremely important for the cell.
If, for instance, the pH of the blood and external fluid is too low (too many H+ ions), then an excess of H+ ions will enter the cell..... making it
But .....
the blood is kept relatively constant is by buffers dissolved in the blood...

Extracellular buffers include bicarbonate and ammonia, whereas proteins and phosphate act as intracellular buffers.

The bicarbonate buffering system is especially key, as carbon dioxide (CO2) can be shifted through carbonic acid (H2CO3) to hydrogen ions and bicarbonate (HCO3-):

H2O + CO2 ↔ H2CO3 ↔ H+ + CO−3

The carbonate buffer ....
Any imbalances in blood pH can be compensated in the short term by changing the rate of breathing.... as this alters the concentration of carbon dioxide in the blood.

E.g. if the blood pH drops too low (acidemia), the body will compensate by increasing breathing, expelling CO2, and shifting the following reaction to the left such that less hydrogen ions are free - thus the pH will rise back to normal.

H2O + CO2 ↔ H2CO3 ↔ H+ + CO−3

For alkalemia, the opposite occurs.
Respiratory Regulation
Carbon dioxide is an important by-product of metabolism and is constantly produced by cells.

The blood carries carbon dioxide to the lungs where it is exhaled

When breathing is increased,the blood carbon dioxide leveldecreases and the blood becomes more

When breathing is decreased,the blood carbon dioxide levelincreases and the blood becomes more

By adjusting the speed and depth of breathing, the respiratory control centers and lungs are able to regulate the blood pH minute by minute

Kidney Regulation
Excess acid is excreted by the kidneys, largely in the form of ammonia

The kidneys have some ability to alter the amount of acid or base that is excreted, but this generally takes several days


pH practical
Watch the couple of pH demos and explanation of buffers
Full transcript