INTRODUCTION TO BASIC HUMAN PHYSIOLOGY
Physiology is the study of the functions of the body at the cellular level.
1-2. LEVELS OF FUNCTION
Function in the human body occurs at three general levels:
a. Molecular. The basic functional entity is the molecule. The structure and
interaction of the molecules of the body is the subject of the science of biochemistry.
b. Cellular. The individual cell is the basis of the structure and function of the
human body. The individual human body consists of great numbers of these cells
working together as a total organism. Groups of like cells performing a common
function are called tissues. Different tissues collected together form individual organs.
Groups of organs performing an overall function are called organ systems, for example,
the digestive system, the respiratory system, etc. When these systems are together in
a single individual, we refer to that individual as an organism. The cellular level of
function is the primary subject matter of physiology.
c. Regional. Here, individual parts of the human body (made up of specific
organs) perform activities as a unit. For example, the hand serves as a grasping,
tool-holding apparatus. The study of this level of function is called functional anatomy.
There is an inseparable relationship between structure and function in the human
body. Every structure is designed to perform a particular function or functions.
Likewise, every function has structures designed to perform it.
1-4. LAWS OF NATURE
The Universe has a fundamental order. The Universe is governed by discrete
and precise laws of nature. These laws are universal, unchangeable, and omnipresent.
The human organism is ultimately controlled by these laws. The organic body of the
human being is essentially operated by the laws of physics and chemistry.
a. Gravitational Force and Mass.
(1) Gravitational force. As you stand upon the surface of the Earth, your
body and its parts experience the force called gravity. The measure of this force is