A Textbook of Practical Physiology CL Ghai
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1A TEXTBOOK OF PRACTICAL PHYSIOLOGY2
3A TEXTBOOK OF PRACTICAL PHYSIOLOGY
Eighth Edition
CL Ghai MBBS MD Formerly Professor and Head, Department of Physiology Government Medical College, Amritsar, Punjab, India Professor and Head, Department of Physiology Government Medical College, Patiala, Punjab, India Professor and Head, Department of Physiology GGS Medical College, Faridkot, Punjab, India Professor and Head, Department of Physiology DAV (C) Dental College, Yamunanagar, Haryana, India
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This book has been published in good faith that the contents provided by the author contained herein are original, and is intended for educational purposes only. While every effort is made to ensure accuracy of information, the publisher and the author specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the contents of this work. If not specifically stated, all figures and tables are courtesy of the author. Where appropriate, the readers should consult with a specialist or contact the manufacturer of the drug or device.
A Textbook of Practical Physiology
First Edition: 1983
Second Edition: 1985
Third Edition: 1987
Fourth Edition: 1990
Fifth Edition: 1999
Sixth Edition: 2005
Reprint: 2006
Seventh Edition: 2007
Eighth Edition: 2013
9789350259320
Printed at
5Dedicated to
Prem Shobhit, Seema and Mehak and Akshay6
7Preface to the Eighth Edition
The first edition of this book was published over 25 years ago. During this period of evolution, the growth and development of the book has been an on-going process depending, as it does, on the feedback received from many teachers and students. They have been generous in their appreciation as well as in their criticism. I have tried to incorporate many of their suggestions in the present edition. I owe them my thanks and hope that I will continue to receive such help in the future as well.
The material included in this book conforms to the syllabi and courses laid down by the Medical and Dental Councils of India from time-to-time, courses that are mandatory and are followed by all colleges.
The 8th Edition has been extensively revised and updated by incorporating the latest concepts and developments in the subject. Figures and text that were not found to be helpful have been deleted/replaced and over twenty-five new Figures/Diagrams have been added.
Questions/Answers, at the end of most Experiments, have been particularly appreciated by junior teachers and students. They are not intended to replace the standard textbooks but only to obviate the necessity for the students to refer to textbooks again and again. They also act as bridges between theory and practical.
A new feature of the book is the introduction of OSPEs at the end of most Experiments—a tool that is being used widely for assessing the practical skills of the students during class tests and university examinations.
Most medical students are overawed and overwhelmed by the enormous amount of medical information available today. Besides, there is the language barrier. Every attempt has, therefore, been made to make the book easily-readable and understandable by our students who come from a wide spectrum of educational backgrounds.
It is a pleasure to acknowledge the valuable suggestions received from many sources. I am particularly indebted to Dr DK Soni, Dr AK Anand, Dr RS Sharma, Dr Ashok Kumar, Dr Parveen Gupta, Dr R Vijayalakshmy, Dr Mrs S Vasugi, Dr P Rajan, Dr Aruna Patel, Dr BS Malipatil, Dr Shailendra Chandar, Dr R Latha, Dr K Sarayu, among others.
I am thankful to Shri Jitendar P Vij (Chairman and Managing Director), M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India and his dedicated team for their enthusiasm in doing an excellent job.
CL Ghai8
9Preface to the First Edition
The material included within the covers of this book conforms to the syllabi and courses of practical physiology laid down by the Medical Council of India, and followed by all the medical colleges. The book is divided into three main sections—amphibian, mammalian and human experiments. There is a separate section on electronic recorders and stimulators. If our students are not to be left behind the rapidly advancing field of medical electronics, they have to be introduced at the earliest to the use of some of these modern devices. The book also supplements the cyclostyled material provided by some physiology departments to their students.
In essence, each experiment begins with the PRINCIPLE on which it is based, and the APPARATUS required for it. Then follow the step-by-step PROCEDURES in which the working instructions are so framed that an average student will find no difficulty in tackling any experiment. Next come the OBSERVATIONS, RESULTS and CONCLUSION. The relevant theoretical aspects of each experiment that are needed for immediate reference, including deviations from the normal, are then described under the heading of DISCUSSION. This is intended to obviate the necessity for the student to refer to the textbooks again and again. Finally, the QUESTIONS generally asked from the students are grouped at the end of the each Experiment. A student should be able to assess his/her comprehension of the relevant material in trying to answer these questions. The APPENDIX contains the units and measures employed in physiology, and the equivalents of metric, United States, and English (Imperial) measures. This is followed by some important reference values of clinical importance. These will certainly prove useful to the hurried and harried medical student for quick reference.
There is continuing controversy and divergence of opinion regarding the necessity of including amphibian experiments in the medical curriculum. Often, these experiments may appear to be time wasting and irrelevant to clinical medicine. However, they have to be included in a book meant primarily for the Indian medical student till such time the courses are revised by the MCI. In any case, they do serve a very useful purpose. They train the students to work with their hands in devising and setting up an experiment, making careful observations, critically analyzing the results and then drawing appropriate conclusions. These are the qualities that the students will depend on later in their clinical work. In fact, the ability to solve problems is the ultimate skill of the physician, and this ability will be honed if the above-mentioned qualities are suitably developed. A compromise can, however, be arrived at; the number of amphibian experiments to be done by the students themselves may be reduced while the rest are demonstrated to them in small groups by their tutors.
The chief aim of the book is to help the students in coping with the problems arising from the handling of various apparatuses during the practical work. If a student has a hazy notion of the purpose of an experiment and the correct technique of carrying it out, he/she will easily be disheartened and frustrated. We hope to help with a clear idea of what he/she is expected to do and a more definite plan of doing it.
It is a pleasure to acknowledge the valuable suggestions received from many friends and colleagues, especially Dr (Mrs) P Khetarpal, Dr (Mrs) Usha Nagpal, Dr Kanta Kumari, Dr RS Sidhu, Dr RS Sharma, Dr Ashok Kumar, Dr Parveen Gupta, Dr OP Mahajan, Dr S Mookerjee, Dr (Mrs) BK Maini, Dr SK Manchanda, Dr OP Tandon, Dr GM Shah, and Dr M Sayeed.
I must express my gratitude to my wife, Mrs Prem Ghai, for her understanding and unstinted support during the long months of collecting the material and the writing of the book.10
I fail to find adequate words to thank my students who prompted and encouraged me in the first instance to write this book. We physiologists recognize the importance of the feedback systems of the body, and so too, is feedback essential for the development of a book. Criticism and suggestions from teachers and students for the further improvement of the book will be thankfully received and acknowledged.
I am indebted to Shri Jitendar P Vij (Chairman and Managing Director), M/s Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India, and his dedicated team for their continued cooperation, enthusiasm and their excellent work in bringing out this book.
May this book act as an effective stimulus for the students to gain first-hand knowledge of experimental physiology, and ease their journey through a complex but fascinating science. As they gather experience, the path will become easier. The discipline of work will then become the most exciting and rewarding experience in their lives.
As they say, “When the going gets tough, the tough get going”.
CL Ghai
17General Introduction
The term “physiology” is derived from a Greek root with a Latin equivalent “physiologia”, originally meaning “natural knowledge” (Physic- = nature; -logy = study of). Though first used by Jean Fernel, a French physician, in 1542, the word “physiology” did not come into common use till the 19th century. The subject of “physiology” now refers to the origin, development and progression of living organisms—from bacterias to vertebrates to trees. Thus, there are many branches of physiology. However, we are primarily concerned with “Human Physiology”, i.e. the functional characteristics of the human body.
It is said that medicine is as old as man, and the growth of our knowledge of physiology is closely linked to the growth of medicine—the mother of all branches of natural science. Chemistry, physics, botany, zoology, pathology, pharmacology, microbiology and their branches have all evolved from the study of the art of healing. And they have, in turn, contributed tremendously to the advancement of medical science. Man is always in search of new and better means of maintenance of health and cure of diseases. This has resulted in new lines of thought and newer methods of investigations from time to time, thus creating new sciences.
It is interesting to note that many of the outstanding physiologists have been well known physicians. We are now aware of the tremendous body of physiological knowledge that has its origin in the study of disease. In turn, the exciting progress in physiology during the last two centuries has greatly enriched our knowledge of disease and put medicine on a scientific footing. The student must, therefore, never lose sight of the fact that the knowledge he/she gains from physiology will form the solid basis of all branches of medicine that he/she will be studying later—pharmacology, pathology, internal medicine, surgery, gynecology, etc.
Over a century ago, William Osler, the famous physician said, “The study of physiology (and pathology) within the past half century has done more to emancipate medicine from the routine and thralldom of authority than all the work of all the physicians from the days of Hippocrates to Jenner, and we are as yet on the threshold.”
 
THE INTERNAL ENVIRONMENT OF THE BODY
Life is believed to have originated in warm seas, which, therefore, formed the external environment of the early forms of life. While these unicellular and few-celled organisms could exchange oxygen and other nutrients, as well as their waste products, directly with the external (or general) environment (i.e. sea water), this process could not operate in multicellular organisms in which most of the cells were located deep within the body. But if these cells could not reach the sea, the sea would have to be brought to them within the body. Each cell in the depths of the body would then be bathed by a fluid with which it could enter into exchanges. This is exactly what is believed to have happened. As evolution proceeded, the external environment was ‘internalized’ and the sea became the tissue fluid (interstitial fluid), which, along with blood plasma, constitutes extracellular fluid (ECF). The evolution of ECF from the sea water is evident from its composition— it has more sodium, chloride, and bicarbonate as compared to intracellular fluid (ICF; the fluid within the cells), which has more potassium, magnesium, and proteins. The plasma membranes (cell membranes) of the cells, because of their selective permeability, keep the two chemical worlds separated from each other.
The adult human body consists of nearly 100 trillion cells (25 trillion of which are red cells), most 18of which live in an “internal sea” of ECF, as described above. Since these cells live within 20–30 μm of blood capillaries, materials can easily pass from the blood into the tissue fluid and thence into the cells, as well as in the opposite direction.
Claude Bernard, a French physician and a great experimental physiologist, employed the term “milieu interior” (internal environment), in the mid 19th century, for the very thin layer of tissue fluid that lies immediately outside each cell. Though the tissue fluid lies outside the cells, it is called the “internal environment” of the body because it has no direct communication with the external or general environment that surrounds the body of an organism.
HOMEOSTASIS—THE BASIC THEME OR PHILOSOPHY OF THE BODY
A necessary condition for the survival of each living cell (and the body as a whole) is that the physical and chemical composition of its immediate surrounding (i.e. interstitial fluid) must not change beyond a certain narrow range, although the external or general environment may show wide changes. For example, the temperature of external environment may vary between −60°C and +60°C, the temperature of the tissue fluid will not change by more than a few degrees.
Though the huge varieties of body cells are organized in tissues, organs and organ systems, they do not function in isolation. Rather they act in such a way that the body as a whole reacts as a unit to any change in the environment. Thus, all the specialized systems of the body—blood, circulatory, respiratory, digestive, locomotor, etc.—have one and only one aim in common, i.e. maintenance of a nearly constant condition of equilibrium or balance in the internal environment of the body. Walter Canon, in 1897, introduced the term “homeostasis” (homeo- = sameness; -stasis = standing still) to refer to the dynamic state of relative stability of the tissue fluid—in terms of its temperature, chemical composition, gas pressures, etc.—the so-called “controlled conditions”.
The nervous system and the endocrine (hormonal) system are the two major communication and control systems that coordinate the activities of all the other systems of the body. The nervous system is a “quick-reaction” system that is concerned with the immediate “short-term” maintenance of homeostasis. The endocrine system, on the other hand, maintains “long-term” homeostasis. In both cases, homeostasis is achieved through a “non-stop” interplay of feedback mechanisms (feedback loops)—some of which function at the macro level (e.g. regulation of body temperature, blood pressure, gas pressures, blood glucose, etc.), while others operate at the micro level, i.e. within the cells. In fact, most of physiology deals with homeostatic mechanisms.
Many factors, within and outside the body, tend to disturb the body's state of equilibrium. If the disturbance is mild, the feedback systems help to quickly restore homeostasis required for health and life. However, if the imbalance is moderate, a disorder or disease may result. If, on the other hand, the imbalance is severe or prolonged, death may occur.
 
EXPERIMENTATION AND OBSERVATION
 
Experimentation
Science is the study of the world around us; rather it is an organized language for describing the world. Experimentation forms the core concept, and a time-honored procedure, in the process of learning about any science.
  1. An experiment consists in making an event occur under certain known conditions, care being taken to exclude as many extraneous factors as possible. Only then observations can be made and proper conclusions drawn.
  2. It is very important for the student to understand the workings of various instruments and apparatuses that she/he will be using. There is a definite protocol or procedure for conducting every experiment. Careful attention given to apparently minor and seemingly unimportant, yet troublesome, points and the precautions to be taken, usually determine the outcome of an experiment. It is an important axiom of science that “mistakes in technique can lead to misleading results”.
  3. The fundamental idea in experimentation is that “you learn by doing”. It is an opportunity provided to the student to gain first-hand knowledge about various aspects of the functioning of one's own body.
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  4. Laboratory work in Physiology is meant to inculcate in the students the habit of carrying out certain procedures in an orderly manner, make careful observations, and draw appropriate conclusion. This will help them in developing scientific skills that will aid them when they approach a problem in clinical setting.
  5. Practical work and theory always complement each other. Therefore, the student must read up as much as possible about the practical and theoretical aspects of an experiment beforehand. Francis Bacon, a great philosopher of science, said, “Read not to contradict, nor to believe and take for granted… but to weigh and consider”. So, read critically and reflectively, with an open mind.
 
Observation
  1. Relations between phenomena can only be revealed if proper observations have been made. Observations should not be passive. Active and effective observations involve noticing something and giving it significance by correlating it with something else noticed or already known.
  2. The student must keep an open mind, forget for the time being, his/her preconceived notions and be on the lookout for the unusual. “Look out for the unexpected” is a good maxim for the medical student.
New knowledge very often has its origin in some quite unexpected observation or chance occurrence arising during an experiment.
Alfred North Whitehead, the famous philosopher says, “First-hand knowledge is the ultimate basis of intellectual life. The peculiar merit of scientific education is that it bases thought upon first-hand observation; and the corresponding merit of a technical education is that it follows our deep natural instinct to transfer thought into manual skill, and manual activity into thought. The thought which science evokes is logical thought.”
 
REPORTING THE RESULTS
  1. Students have a common tendency to report their observations and results similar to those described in the books. One should always remember that the result of an experiment is, strictly speaking, valid only for the precise conditions under which the experiment was conducted.
  2. It is well-known that the accuracy with which an experiment is conducted varies from person to person. Therefore, if your results are at variance with those expected, some unrecognized factor or factors might be operating. Such occurrences must always be welcomed, because the search for the unknown factor may lead to an interesting discovery. It is when experiments go wrong that we find things out.
 
INSTRUCTIONS TO THE STUDENTS
  1. Check the laboratory schedule a day earlier and read up the relevant material in the practical physiology book. This will help you to plan and organize each experiment.
  2. Pay due attention to the practical demonstration given by your teacher before each experiment.
  3. Always bring your practical physiology book as well as your practical work-book (file) to the laboratory.
  4. Check out the apparatus being issued to you by the laboratory technician at the distribution table, and see that it is in proper working condition. This will avoid frustration and wastage of time once you start your work. You will be required to sign for the apparatus and return it after completing your work. If there is any breakage or damage to the apparatus, it must be reported to the teacher-in-charge.
  5. As you may be working in groups of two, you should not expect nor depend entirely on the efforts of your work-partner to do most of the work. Each student is expected to be able to independently carry out each experiment.
  6. As you and your partner will be acting as the ‘subject’ in human experiments and clinical examination, try to be gentle and considerate. You will need these qualities later when you handle patients.
 
Important
As you start each practical, be certain to go through the “Student objectives” at the start of each 20experiment. This will help you to focus on what is important and what is expected from you.
 
LABORATORY DISCIPLINE
  1. Wear a clean overall, as it constitutes an essential part of laboratory discipline.
  2. The working area on the worktable must be kept clean and the equipment placed in proper and convenient locations. Avoid clutter.
  3. Do not throw any used cotton/gauze, pieces of paper, etc. into the sink.
  4. Do not indulge in idle gossip. However, discussions with your work-partner and other students will be of tremendous help.
  5. Guidance from your teacher is always available and should be actively sought and welcomed.
  6. Equipment. The department will provide most of the equipment needed by you. However, you must bring your own colored pencils (blue, heliotrope, black lead, etc.) ruler, rubber, clean piece of cloth, etc. You will be told about other instruments (e.g. stethoscope, percussion hammer, etc.) required for “Human Experiments”, “Clinical Examination,” and “Amphibian Experiments”.
 
WRITING RECORDS
  1. The practical notebook should be of good quality paper, blank (unruled) on the left side for diagrams, and ruled on the right side for description of the practical work.
  2. Every student must keep a record of the demonstrations attended and experiments conducted. Get every experiment signed from your teacher regularly. Make an index of your work in your notebook, and get each entry initialed by your teacher.
  3. Remember that Relevance, the Principle on which the experiment is based, Observations and Results, Conclusions and the Precautions taken constitute an important part of your training in basic scientific work. Enter all this material in your notebook.
  4. Observations and results should be properly entered, and diagrams, graphs and tables prepared as and when needed.
  5. Variations under normal and abnormal conditions form an important part of a medical experiment. These should also be recorded.
 
SUGGESTIONS FOR TUTORS/JUNIOR TEACHERS
  1. Teachers are managers of the learning process of the students. Every student needs help and guidance in her/his learning process and teachers are meant to fulfill this need.
  2. Teachers have great responsibility of inculcating discipline and work culture in their students.
  3. They must ensure that the students do not indulge in idle gossip. However, they should be easily accessible to the students in need of guidance.
  4. Students are generally afraid to seek help and ask questions out of fear of the teacher, or out of a fear of exposing their ignorance of the subject and cutting a sorry figure in front of other students. They need to be assured that it is all right to ask questions (and even make mistakes in the process). In these days of knowledge explosion, nobody can even hope to know everything even about a limited part of knowledge available.
  5. Junior teachers should acquaint themselves thoroughly with the subject so that they can help students effectively.
 
STUDENT OBJECTIVES
Any organized study for the acquisition of knowledge involves clear-cut ideas about the objectives or the purpose of the study. Each practical (experiment), therefore, starts with certain objectives that a student is expected to know and achieve in knowledge and skills.
The Student Objectives form the basis of what the student is expected to do in each practical and know its practical applications. The student must go through these before starting the practical as well as afterwards. She/he can then assess if she/he has achieved the desired objectives and skills.
 
Assessment of Students' Practical Skills
The assessment of students in ‘practicals’ during the class tests and final examination has been largely a subjective process. Usually, the student has finished 21his/her practical task by the time the examiner comes to assess his/her work. Questions are asked and what is usually assessed is his/her knowledge rather than his/her practical skills. (In some practicals, he/she is asked to perform a part of his/her practical, such as, focusing a leukocyte under the microscope, eliciting a reflex, recording the blood pressure, etc.) Depending on the experience of the examiner, marks/grades are awarded. This method has stood the test of time and proved quite satisfactory.
However, the trend has changed during the last few years in many medical colleges.
In addition to long and short experiments, spotting, charts, and grand viva, etc. the student is asked to carry out part of a practical according to clearly defined aim within a given period of time (usually 4–5 minutes)—a tool called OSPE (Objective Structured Practical Examination), and OSCE (Objective Structured Clinical Examination).
 
METHODOLOGY OF OSPE
Conducting OSPE requires much organization and planning. It involves setting important and relevant questions and preparing accurate and clear-cut checklists. The student moves around a number of work-stations (usually 4 to 6), performs the given task at each in 4–5 minutes and moves to the next in response to a signal (bell). While the student performs the given task, the examiner, with the checklist in hand, stands beside his/her and watches every step, grading his/her accordingly. The examiner does not ask any questions, nor answers any queries by the student.
The chief advantage of OSPE is that it is purely an objective tool; there is no examiner's bias, nor any other extraneous factor operating.
The setting up of work-stations requires that all the equipment needed at a station is provided beforehand. The checklists also must be ready for the examiners.
Note. The OSPEs given in this book are mostly to act as guides. These can be altered, changed or modified according to local requirements. It is important that the students be exposed to OSPE tests during routine class tests to acquaint them with the methodology.