A Lifestyle Consultant's Course in Natural Living - Sample Lesson 74

Subject: Physiology

By John L. Fielder

Introduction to Physiology


The word physiology is derived from two Greek words—physis, meaning Nature or natural science, and logos, meaning study of or discourse—and is that science which deals with the functions of living organisms and their parts, in contradistinction to anatomy, which deals with the structure of living organisms.

Animal physiology deals with and is the study of the functions of animals, while the term human physiology is that of human beings.

As it is impossible to understand the various parts of the body without knowledge of their structure, we have commenced your studies with those of anatomy.

Humans belong to that division of the animal kingdom known as vertebrates, from the Latin vertebra, meaning a turning joint, that is, humans are characterised by a possession of a long dorsal chain of morable bones—the vertebral column.

The human being, then, is a vertebrate animal in the class mammalia. This division comprises fish, amphibians, reptiles, birds, and mammals, humans belonging to the class of mammals whose characteristics are those of having breasts for suckling their young, and the occurrence of hair on their bodies.

Humans are in the order primates and, along with monkeys and apes, belong to the suborder anthropoidia. Because so many of human features resemble those of monkeys, humans are classed with apes in the superfamily hominoidia. Humans are the tallest of the hominoidia, and only the some times surpasses them in size. Superficially, humans appear to have a relatively primitive structure—to be a seemingly hairless ape—with a large brain, and to retin certain foetal characteristics in their adult anatomy.

Humans are bi-pedal, walking upright— orthograde—on their soles, in a plantigrade fashion. This type of locomotion is associated with numerous adaptations of the skeleton from the foot to the skull.

Since the upper limbs are not needed for locomotion, as is often the case in other primates, man can use them for prehension (grasping, seizing), particularly since the arms are strutted to the body by a collarbone— clavicle. The human forearm is long and can be rotated with the arm by the side so that the palm faces forward (supinated)-or backward (pronated). The large thumb-pollex-can be opposed to each of the other fingers, to grasp either delicately or powerfully. The expanded pelvis, which helps to support the Internal organs—viscera, has a capacious cavity, associated in the female with the birth of a large-headed foetus. The legs are long and greatly strengthened, the hip in the upright position is extended, as is the knee joint certain muscles involved in walking are enlarged. The great toe—hallux—is large, and the bones of the feet are arched. The skull possesses a large cranial cavity; the face is oriented forward in the upright position, and the head is poised above the vertebral column. Although humans have a prominent chin, their jaws are weak and their teeth are small.

Human beings are probably the longest lived of all the mammals.

A social, gregarious, and political animal, humans lead a complex existence, with a unique culture and an aesthetic sense. They display various degrees of freedom from conduct enforced by primitively predetermined responses in behaviour. Humans are educable and can develop complex mental processes. They can communicate in many ways, principally by articulate speech and thoughts and symbols.

To return to our original thesis, physiology is the study of the functions of the body as a whole, and of the individual structures and organs contained therein. Some of this is reasonably simple; some involves complicated chemical physical and electrical details.

Every living structure, whether it be animal or vegetable, is derived, so fat as we know, from another living structure. It has the power of growth and reproduction, and its life is dependent upon its ability to absorb non living material, which it builds up into the framework of its own body.

Before we consider living matter, it is necessary to go back a step further and ascertain the nature of the chemical sub stances of which it is composed, which are, therefore, found in the human body as a whole.

Broadly speaking, there are two types of matter:

  1. Elements; and
  2. Compounds.

The latter may he divided into inorganic and organic.


An element is a substance which contains only one kind of matter. A simple substance, which cannot be decomposed or further reduced, by other than chemical means. An element is made of atoms which are alike in their peripheral electronic configuration— chemical properties—but which may differ in their nuclei, and so in their atomic weight and their radioactive properties.

The following are the most important elements found in the human body:

Carbon, Hydrogen, Nitrogen, Oxygen, Iodine, Sulphur, Phosphorous, Chlorine, Sodium, Iron, Potassium, Magnesium, Calcium.

Of these, oxygen and nitrogen sometimes occur in their uncombined natural state. The balance is to be found combined with one another in the form of compounds.

Certain elements have the peculiar ability to change spontaneously into other elements. These elements are called radioactive elements, the best known being radium.

In chemistry there is in excess of 100 named elements.


A chemical compound is a combination of two or more elements in fixed proportions, forming an entirely new substance in which the individual elements apparently lose their identity, thereby differing from a simple mixture. Every part of a compound has exactly the same composition and properties as every other part.

Inorganic compounds are relatively simple compounds of the elements found especially in non-living matter such as minerals, water, and salts.

The essential feature of organic com pounds is the presence of the element carbon, usually combined with hydrogen and oxygen. in addition, nitrogen and other elements may also be included and form compounds of a highly complicated nature, which are found specially in living matter.

The two main organic compounds found in the body are:

  1. Carbohydrates containing carbon, hydrogen, and oxygen
  2. Fats containing nitrogen and other elements in addition to the above
  3. Proteins containing nitrogen and other elements in addition to the above.

Going back one stage further in the structure of matter, and in order to understand some of the principles which must he considered in physiology, it is necessary to have some knowledge of the Atomic Theory, which was propounded by Dalton over one hundred fifty years ago. This has been the basis of chemical science ever since.

Atomic Theory

When elements unite with each other to form a compound, a definite weight of each element combines with definite weights of the other elements.

Atoms in this state of ionisation, because they carry an electrical charge, are referred to as electrolytes, and the solution containing them, an electrolyte solution.

It is in this form that many salts circulate in the water contained in the blood and tissue fluids of the body.

Another aspect of this subject is the “acid/alkaline” reaction of body fluids. The hydrogen ions (H+) have a positive charge and are acid, while the hydroxyl ions (HO—) are negative and cause alkalinity. If the H ions and the HO ions are equally balanced, the reaction of the fluid will be neutral:

H+ + HO = H2O (or water, which is neutral).

For practical purposes a scale has been devised and numbered from 1 to 14. The central figure of 7 is taken to represent neutrality and the hydrogen ion concentration is indicated by the symbol pH.

Fluids having a pH of 1 to 7 are acid and those with a pH exceeding 7 are alkaline.

It must be understood that this is a scale only used to measure very small degrees of acidity and alkalinity. For example, the pH of the blood is kept constant at 7. ie, very slightly alkaline but never acid. That of the urine is usually slightly acid, with a pH of 5 to 6.

One of the most important functions of the various salts present in the body is to keep the pH of the blood constant, and there is a constant interchange of various positive and negative ions in the tissues to maintain the equilibrium. Any excess of acid hydrogen ions are excreted in the urine by the kidney cells.

On the other hand, one of the most important end products of carbohydrate and fat metabolism is carbon dioxide, CO. When this is dissolved in water, it forms a weak acid—carbonic acid: H H + CO.

This, when ionised, also liberates acid H ions in considerable quantity, which would tend to lower the pH of the blood towards the neutral figure of 7. However, the respiratory centre in the medulla of the brain is particularly sensitive to any change in the pH of the blood, and immediately causes an increase in the rate and depth of breathing, which is maintained until the excess of carbon dioxide (and at the same time, excess of hydrogen ions in the blood) is removed.

There are also certain salts, together with the blood plasma that are neutral, but which have the power of reacting with hydrogen ions without becoming acid. These are called buffer substances, which also help to maintain the pH of the blood at a constant level.


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