D.F. Horrobin – författare

of these subjects and should be kept constantly at hand so that it can readily be consulted when difficult topics arise. I hope that it may succeed in reducing the fear with which many nurses face the sciences with which the book deals. Section 1 BIOLOGY 2 The cell and its requirements The world of living things is conveniently and conven­ tionally divided into two great groups, the animals and the plants. Broadly speaking the important feature which distinguishes plants is that they can manufacture most of the substances they require by trapping and using various forms of outside energy, in particular the energy of sunlight. In the process of photosynthesis they utilize the energy of light to build up complex chemical substances from relatively simple ones. In contrast, animals lack the ability to use light or any other form of outside energy. Instead they must obtain the energy they require by breaking down complex substances which ultimately they always obtain from plants. Plant-eating animals such as cows and sheep obtain these substances directly. Carnivores obtain them indirectly after they have passed through the bodies of other animals.

Biochemistry is the study of the chemistry of living organisms, of the ways in which food is used to serve all the many needs of the body. Biochemistry is closely connected with nutrition, the study of the types and amounts of various materials required in the diet. Biochemistry is also inextricably int~rtwined with endo­ crinology, the study of hormones, for most of the hormones exert their actions by altering the behaviour of chemical reactions within the body. The central problem in biochemistry is that of the supply of energy. Energy is needed for a multitude of purposes of which muscular activity is the best known. Energy is required for digestion, and for the functioning of the kidney, the liver, the brain and all the other organs in the body. Energy is also essential for the building up of the complex organic molecules of which the body is con­ structed. Ultimately, most of the energy utilized on earth comes from the sun. Plants are able to tap this energy source directly by the process of photosynthesis. By using pigments, notably the green chlorophyll, plants can trap the energy of sunlight and use it to build up complex substances such as fat, carbohydrate, protein and nucleic acids. The only raw materials required are carbon dioxide, water and simple inorganic substances such as nitrates which can be extracted from the soil.

to Human Physiology D. F. Horrobin Published by MTP Press Limited SI. Leonard's House, Lancaster, England Copyright © 1973, D. F. Horrobin ISBN-13: 978. . ()-85200-048-9 e-ISBN-13: 978-94-010-2349-8 001: 10. 1007/978-94-010-2349-8 First pUblished 1973 No part of this book may be reproduced in any form without permission from the publishers except for the quotation of brief passages for the purpose of review Reprinted 1975 and 1976 by the Blackburn Times Press, Northgate, Blackburn BBZ lAB Contents Introduction 2 The Maintenance of a Constant Internal Environment 7 21 3 Biochemistry The Nervous System 45 4 The Endocrine System 5 79 The Body Fluids and Blood 6 93 7 Circulation 105 8 The Respiratory System 119 9 The Kidneys and Urinary Tract 129 10 The Alimentary Tract 137 11 The Reproductive System 145 12 Responses of the Whole Body 159 An Introduction to Human Physiology Author's Preface In many fie1dliof study it is difficult to understand the sig­ nificance of the part before one understands the whole. Yet one cannot understand the whole without a prior understanding of the parts. The dilemma is one of the most difficult problems to be solved by the teacher and in no subject is it more important than in physiology. In physiology more than in most subjects the part serves the whole and the whole serves the parts in an extraordinarily intimately integrated manner.

Physiology is the study of the normal working of the body. It is essential that its principles should be understood by nurses and doctors, for only if you know how the body works normally can you understand what is happening during disease. This first chapter covers the whole of physiology in outline, so that as later you read the chapters devoted to giving details of the various systems, you will be able to see where each system fits into the scheme of things. THE CELL You can learn a great deal about physiology by considering the requirements of a simple, single-celled organism such as the amoeba. These requirements may be summarized as follows: 1. Supplies. All living organisms require a supply of energy if they are to survive. Plants can obtain their energy directly from the sun and by using very simple inorganic materials they can manu- facture all the substances they need. But animals must obtain their energy from the complex materials which they take in as food. The energy is released by the process known as oxidation (burning), in which food is broken down and combined with oxygen to release all the energy which is required.Animals therefore obviously need a supply of food and a supply of oxygen. Since the animal body is largely made up of water, they need a supply of water as well. The amoeba finds it easy to obtain all these materials from the water which surrounds it.

The two subjects which have been previously widely covered, the roles of prolactin in lactation and in rat mammary cancer, are presented relatively briefly though with a full list of references.