ZOO502 Handouts Topics 1-265

CHAPTER-1 · GENERAL THEMES IN PHYSIOLOGY · TOPIC 1 · THE SPECTRUM OF STUDY OF PHYSIOLOGY · Physiology—Definition

Animal Physiology deals with the study of functions of the tissues, organs and organ systems of animals.

The ultimate goal of the study of physiology is to understand the mechanisms that operate in animals at all levels, in physical and chemical terms.

Physiological Mechanisms Obey Laws of Physics and Chemistry:

The knowledge of Physiology is firmly rooted in the laws and concepts of physics and chemistry. Following are the examples of some physical and chemical laws and concepts that relate to various physiological processes:

Ohm’s Law—applies to blood flow and pressure; ionic current; capacitance of membranes. Boyle’s Law and the Ideal Gas Law—apply to respiration. Law of Gravity—applies to blood flow. Concepts of kinetic and potential energy—apply to muscle contraction; chest movements during inhalation and exhalation. Concepts of Inertia, momentum, velocity and drag—apply to animal locomotion.

These are just a few examples. Many more physical and chemical laws and concepts are used to explain various physiological phenomena.

Curiosity underlies the learning of Physiology

Underlying all studies of animal physiology is the curiosity (desire to know) about how animals and their systems work. e.g.

How can a Hummingbird’s heart beat 20 times a second during hovering flight?

How do insects see in the ultraviolet spectrum?

How do kangaroo rats survive in the desert with no access to drinking water?

Such questions fuel the curiosity of animal physiologists and there is no bound to this curiosity. The more we know, the more we realize how little we know about physiological systems of animals.

From Animal Physiology to Human Physiology

Study of animal physiology has provided an insight into the physiological processes of humans. The human species shares the same fundamental biological processes with all other animal species and has a linked evolutionary history.

To illustrate this relationship let’s give few examples: The heart beat in the human body results from the same physiological mechanisms that underlie heart function in fishes, frogs, snakes, birds, or apes. Similarly, the molecular events that produce an electrical nerve impulse in the human brain are fundamentally the same as those that produce an impulse in the nerves of a squid, crab or rat.

For these reasons, the study of animal physiology has made innumerable contributions to understanding human physiology. In fact, most of what we have learned about the functions of human cells, tissues, and organs was known first through the study of various species of vertebrate and invertebrate animals.

While animal physiology lays the foundation of human physiology, the human physiology is the foundation of scientific medical practice. Understanding of the functioning and malfunctioning of living tissues provides the foundation for developing effective, scientifically sound treatment for human diseases.

In the modern times, animal physiology has contributed through new techniques for generating unique animal models for specific human diseases (e.g., diabetic mice, congenitally fat rats, zebra fish embryos with heart defects). These models allow a wide range of experiments that provide the insights into the underlying physiological processes of such diseases and defects.

TOPIC 2

CENTRAL THEMES IN ANIMAL PHYSIOLOGY

Our major goals of study of animal physiology are to:

explore the physiological processes that are basic to all animal groups show how they have been shaped by selective forces during evolution

Comparing and contrasting how different organisms have adapted to survive similar environmental challenges provides useful insights about the patterns of physiological evolution and the adaptive value of physiological processes.

Central themes in animal physiology:

As we study animal physiology and physiological adaptations, we notice several basic themes, repeatedly emerging.

We shall briefly discuss five major themes here, i.e.

(i) Structure-function relationships (ii) Adaptation, Acclimatization and Acclimation (iii) Principle of homeostasis (iv) Feedback control systems (v) Conformity and Regulation