by Talib F. Abbas
 Physiology, study of the functioning of living
organisms, animal or plant, and of the functioning of
their constituent tissues or cells.
 Discoveries of unity of structure and functions
common to all living things resulted in the
development of the concept of general physiology, in
which general principles and concepts applicable to all
living things are sought.
 The publication in 1628 of Harvey’s Exercitatio
Anatomica de Motu Cordis et Sanguinis in
Animalibus (An Anatomical Dissertation Upon the
Movement of the Heart and Blood in Animals) usually
is identified as the beginning of modern experimental
physiology.
 Elementa Physiologiae Corporis Humani (Elements of
Human Physiology) by Albercht Von Haller.
 Claude Bernard in France; Johannes Müller, Justus von
Liebig, and Carl Ludwig in Germany; and Sir Michael
Foster in England may be numbered among the
founders of physiology.
 Many important ideas in physiology were investigated
experimentally by Bernard, who also wrote books on
the subject. He recognized cells as functional units
of life and developed the concept of blood and body
fluids as the internal environment (milieu intérieur) in
which cells carry out their activities.
 The very fact that we remain alive is almost beyond our
control, for hunger makes us seek food and fear makes
us seek refuge.
 Homeostasis in a general sense refers to stability,
balance or equilibrium. It is the body's attempt to
maintain a constant internal environment.
Maintaining a stable internal environment requires
constant monitoring and adjustments as conditions
change.
 For example, in regulating body temperature there are
temperature receptors in the skin, which communicate
information to the brain, which is the control center,
and the effector is our blood vessels and sweat glands
in our brain.
Homeostasis
 The ECF is more dilute than present-day seawater, but
its composition closely resembles that of the
primordial oceans in which, presumably, all life
originated.
 the ECF is divided into two components: the
interstitial fluid and the circulating blood plasma.
The plasma and the cellular elements of the blood,
principally red blood cells, fill the vascular system, and
together they constitute the total blood volume.
 In the average young adult male, 18% of the body
weight is protein and related substances, 7% is
mineral, and 15% is fat. The remaining 60% is water.
The intracellular component of the body water
accounts for about 40% of body weight and the
extracellular component for about 20%. Approximately
25% of the extracellular component is in the vascular
system (plasma = 5% of body weight) and 75% outside
the blood vessels (interstitial fluid = 15% of body
weight). The total blood volume is about 8% of body
weight.
 The extracellular fluid contains large amounts of
sodium, chloride, and bicarbonate ions plus nutrients
for the cells, such as oxygen, glucose, fatty acids, and
amino acids.
 The intracellular fluid differs significantly from the
extracellular fluid; specifically, it contains large
amounts of potassium, magnesium, and phosphate
ions instead of the sodium and chloride ions found in
the extracellular fluid.