LESSON ASSIGNMENT
LESSON 1 Introduction to Basic Human Physiology.
LESSON ASSIGNMENT Paragraphs 1‑1 through 1‑10.
LESSON OBJECTIVES
After completing this lesson, you should be able to:
1‑1. Define physiology.
1‑2. Describe the levels of function and the relationship between structure and function in the human body.
1‑3. Identify the effects of fundamental laws, concepts, and forces
of the Universe.
1‑4. Identify processes which distinguish living from nonliving objects.
1‑5. Match three somatotypes with their descriptions.
1‑6. Identify general body functions and their descriptions.
1‑7. Identify fundamental processes for providing energy to human
beings.
SUGGESTION After completing the assignment, complete the
exercises at the end of this lesson. These exercises will help you to
achieve the lesson objectives.
LESSON 1
INTRODUCTION TO BASIC HUMAN PHYSIOLOGY
1‑1. DEFINITION
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.
1‑3. INTERRELATIONSHIPS
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 called weight. Gravity is one type of gravitational force, a force which attracts all particles and bodies to each other. Gravity acts upon your body during every instant of your life.
(2) Mass. If you were standing on the surface of the Moon, you would weigh 1/6 of your weight on Earth, but your mass would remain the same. Mass is an intrinsic property of a particle or object that determines its response to a given force. In a given location, the weight of an object depends upon its mass.
b. Space and Time. Each individual occupies a certain amount of space. We exist over a span of time. During the passage of time, we change‑‑from an infant, to a child, to an adult, to an adult of advanced age.
c. Physical States of Matter. The matter around and in us exists in several states. These various states generally reflect the closeness of the molecules that make up the matter.
(1) Solid. The most compact organization is the solid, which retains its specific form and shape.
(2) Liquid. Liquids tend to flow but still stay together.
(3) Gas. Gases also flow but are widely spread and will readily dissipate in many directions.
d. Pressure Gradients. Substances that flow (gases and liquids) flow in very specific directions. They flow from an area of higher pressure or concentration to an area of lower pressure or concentration as long as the two areas are freely interconnected. The difference in pressures of two interconnected areas is called a pressure gradient. When plotted on graph paper, it is in the form of a slope. The greater the difference, the steeper is the slope and the faster the material flows.
1‑5. MECHANICS/BIOMECHANICS
Machines are devices that do work. The different kinds of machines and their modes of action are the study of applied mechanics. The human body, as already stated, conforms in its structural organization to the laws of physics. The body uses several different kinds of machines, such as levers, pulleys, and valves, in its operation. We refer to these operations as biomechanics.
1‑6. LIFE PROCESSES
The planet upon which we live is composed of inanimate (nonliving) materials such as minerals, water, etc. Living organisms reside upon or in this mass of nonliving material. You can distinguish living from nonliving material by the fact that living material carries on a series of functions known as the life processes. A living thing takes in substances, grows, moves, is irritable, and reproduces. Often, it is difficult to distinguish between living and nonliving materials. But in the ultimate analysis only living materials perform all of these functions.
1‑7. VARIATIONS AMONG HUMAN ORGANISMS
The human organism is known scientifically as Homo sapiens, meaning the intelligent human being. There is a more or less common form for human beings. This common form includes one head, two upper members, two lower members, etc., but there are no two individuals exactly alike in detail. (This even includes identical twins. One tends to be left‑oriented and the other right‑oriented.) As a result, there is a tremendous variation among humans which has been further complicated by selection and propagation of specific traits by humans themselves.
1‑8. SOMATOTYPES
Given the variations among human organisms, various methods of categorization have been established to achieve some common order. The method we will use is referred to as somatotyping. See Figure 1‑1.
Figure 1-1. Human somatotypes.
a. In this method, human beings are categorized into three different groups:
(1) Ectomorphs, who tend to be thin‑bodied individuals.
(2) Endomorphs, who tend to be broad‑bodied individuals.
(3) Mesomorphs, who have a body form between the other two.
b. It has been demonstrated that there are significant differences among human beings in these categories. These differences exist not only in body form but also in internal anatomy of structures and susceptibility to diseases.
1‑9. GENERAL BODY FUNCTIONS
The living human being performs many functions as a part of daily life.
a. Nutrition. The body takes in materials for energy, growth, and repair. Since the body cannot produce its own energy, it must continually take in foods to supply that energy to carry on the life processes. This food also provides materials for growth and repair of the cells and tissues.
b. Motion and Locomotion. Being an erect, standing organism, the body requires special supporting structures. At the same time, it needs a mechanical arrangement to allow the parts to move (motion) and to move from place to place (locomotion).
c. Reproduction. For the species to continue, there must be reproduction, the formation of new human beings belonging to subsequent generations.
d. Control. All of this activity is controlled by three major systems of the body‑‑heredity/environment, hormones, and the nervous system. Hormones provide a chemical control system. The nervous system works much like circuitry in a computer. In the final analysis, however, all of the structures and functions of the body are determined by special units called genes, the study of which is genetics and the transmission of which is heredity. Heredity determines the potential range of an organism's characteristics. The environment determines which potential characteristics are developed and to what degree.
1‑10. ENERGY
As we have previously mentioned, energy is required to carry on the life processes of each individual human being.
a. One of the laws of nature is conservation of energy. This means that energy cannot be created or destroyed but only transformed. For example, electricity can be transformed into heat. The human body cannot produce energy on its own and must, therefore, continuously take in a fresh supply of energy.
b. Except for a few special situations, all of the energy for living matter on Earth is received from the Sun through solar radiation. Green plants trap and bind this solar energy in molecules of glucose by the process of photosynthesis.
c. Humans take this glucose into their bodies directly by eating green plants or indirectly by eating the flesh of plant‑eating animals. The human body releases the trapped energy from glucose by a process known as metabolic oxidation.
d. The released energy is used to form the compound ATP (adenosine triphosphate) from ADP (adenosine diphosphate). ATP is like a charged battery; the "discharged battery" is called ADP. Molecules of ATP are present in all of the living cells of the body. Within each cell, molecules of ATP are "discharged" to release a large quantity of energy to drive the various life processes. Through further metabolic oxidation, the resulting ADP molecules are "recharged" to form ATP molecules once again.