Regulate the acidity (pH) of the blood
Help regulate the level of oxygen in the blood
Are involved in moving nutrients into cells and waste
products out of cells
Description
Water is essential to life.Dehydration occurs
when more water is lost from the body than is
replaced. A loss of 20% of the body’s water can be
fatal. Water balance and electrolyte concentrations
are closely intertwined. Dehydration is a major cause
of electrolyte imbalances.
Electrolytes, proteins, nutrients, waste products,
and gasses are dissolved in fluid in the body. This fluid
is not distributed evenly. About two-thirds of it is
found inside cells (intracellular fluid). The rest is
found in the spaces between cells (interstitial fluid),
in the circulatory system, and in small amounts in
other places such as the stomach. Changes in the con-
centration of electrolytes results in changes to the dis-
tribution of water throughout the body as water
moves into or out of cells.
The components of body fluid—electrolytes, pro-
teins, and so forth—are not evenly distributed either.
Different types of cells have membranes that allow
some electrolytes (and other components of the fluid)
to pass across them while blocking others. This differ-
ence in the distribution of electrolytes (and thus elec-
tric charges) on either side of cell membranes makes it
possible for many metabolic reactions to take place.
Water passes easily across cell membranes. When
fluid with two different concentrations of electrolytes
is separated by a cell membrane, there is pressure
(called osmotic pressure) for water to flow across the
membrane from fluid that contains fewer electrolytes
(less concentrated) into fluid that contains more elec-
trolytes (more concentrated). The cell uses energy to
resist osmotic pressure and maintain different concen-
trations of electrolytes on either side of the membrane
because even small changes in the concentrations and
distribution of electrolytes can result in large move-
ments of water in and out of cells. Maintaining this
difference, or gradient, across cell membranes is a
major part of the complex regulatory events called
homeostasis that keep conditions within the body sta-
ble within very narrow limits. When there is an imbal-
ance in electrolytes many systems in the body are
affected and serious, even fatal, health problems can
result.Causes of electrolyte imbalances
An electrolyte imbalance occurs when the concen-
tration of a specific electrolyte is either too high or too
low. The concentration of electrolytes is strongly
affected by the amount of fluid in the body. Fluid
balance is largely controlled by hormones that act on
the kidneys and regulate how much urine the kidneys
produce. The average male adult loses about 1.5-2.5 L
of water daily through urine production, sweating,
breathing out water vapor, and bowel movements
depending on exercise levels and environmental temper-
ature. The United States Institute of Medicine recom-
mends that adult men drink a minimum of 3 L of liquids
a day, and that women drink a minimum of 2.2 L to
replace lost water.
Dehydration is a major cause of electrolyte imbal-
ance. It occurs whenever water is lost from the body
and not replaced fairly quickly. When fluids are lost,
electrolytes in those fluids are lost too, increasing the
risk of electrolyte imbalance. Dehydration can be
caused in many ways. These include:
Heavy exercise, especially in hot weather. Sodium
and water are both lost through the skin with heavy
sweating.
Limited fluid intake. This is a particular problem
with the elderly, especially those who are unable to
walk or are bedridden.
Severe vomiting and diarrhea. Large amounts of
water and many electrolytes that would normally
be absorbed in the intestines are lost with diarrheaKEY TERMS
Diuretic—A substance that removes water from the
body by increasing urine production.
Glucose—A simple sugar that results from the
breakdown of carbohydrates. Glucose circulates
in the blood and is the main source of energy for
the body.
Homeostasis—The complex set of regulatory
mechanisms that works to keep the body at optimal
physiological and chemical stability in order for
cellular reactions to occur.
Hormone—A chemical messenger produced by
one type of cell and travels through the blood-
stream to change the metabolism of a different
type of cell.
Serum—The clear fluid part of the blood that
remains after clotting. Serum contains no blood
cells or clotting proteins, but does contain
electrolytes.Electrolytes