Have you ever wondered how physiology is different from medicine? Did you know that there are physiologists who study plants or bacteria or fungi? This lesson describes what physiology is and offers a brief history of how the field developed.
What Is Physiology?
Physiology is the study of how organisms function. The physi- part of the word comes from a Greek word that is broadly translated as ‘natural origin.
‘ The same root is used to form the words physician, physical, and physics. When we think of physics today we think of the study of how matter and energy work, but another way to think about physics is as a study of how nature functions. In that sense, physiology is also a study of how nature functions – in this case, within a living organism. Physiology can be divided into many sub-fields, including plants, animals, bacteria, and more, but most early physiology records focused on how human systems work.
Levels of Organization
An organism can be broken down into different levels of organization, all of which can be studied by physiologists. Within an organism are multiple organ systems, like the digestive system and the respiratory system. These organ systems are typically made up of multiple organs and glands.
An organ is a distinct structure that has a specific function within an organism. For example, the stomach is an organ that is part of the digestive system. In the stomach, food is both mechanically and chemically broken down to make it easier to absorb nutrients.Organs are made up of one or more types of tissue. A tissue is a collection of cells that have similar structures and function. Smooth muscle is a type of tissue that makes up a large portion of the stomach. At the smallest level of organization is a single cell from a tissue.
For example, a single muscle fiber within a muscle. Some physiologists study how the parts within a cell work or how different proteins or chemicals interact within a cell.
History of Physiology
Physiology has long been studied together with anatomy and medicine.
Ancient civilizations from Greece, Egypt, India, and China all have written records describing human physiology and treatments for various diseases. The history of physiology in Europe during the Renaissance from the 16th to the 18th century was greatly influenced by classical Greek works of natural philosophers such as Hippocrates, Aristotle, and Galen. The term physiology was first used by 16th-century French physician Jean Fernel.
Advances in physiology greatly accelerated in the 19th century with the proposal of cell theory and the concept that cells maintain themselves through their environment. Cell theory, proposed by German biologists Matthias Schleiden and Theodor Schwann, states that all living things are made of cells, and the cell is the basic structural unit of life. The idea that cells maintain themselves through supportive and nutritive extra-cellular fluids, originally termed milieu interieur (environment inside), was first described by French physiologist Claude Bernard.
This was expanded on by American physiologist Walter Cannon who used the term homeostasis to describe how cells maintain themselves within a range of normal function. Greater technological advances and understanding of genetics have further accelerated the amount of physiological knowledge gained in the 20th century and today.Early physiologists often experimented on themselves or sometimes even their students! In modern times, human experimentation is rarer and very carefully regulated to follow ethical standards. Most physiology experiments today use what are called model systems. These model systems are designed to be similar to human physiology. Often times, animals are used in place of humans. These include the commonly mentioned lab rat and guinea pig.
In fact, there are many different strains of lab rat used in physiology studies, often bred for specific characteristics. For example, there are rat strains that spontaneously develop hypertension (high blood pressure) and others that develop diabetes. Other model systems may consist of isolated organs, tissues, or cells. These types of preparations are called reduced preparations because they do not use a whole organism.
This allows an experimenter to isolate certain types of cells or tissues or specific physiological processes. Mathematical and computer models are also used sometimes to predict physiological processes.
For all of recorded history, humans have shown interest in how their bodies work and why certain things may stop working. Physiology is the study of how an organism functions and what factors may cause those functions to change.
Western physiology owes its beginnings to classical Greek writings. The concepts of cell theory and homeostasis are two key concepts that helped propel modern physiology.Cell theory states that all organisms are made of cells, and cells are the basic structural unit of an organism. Homeostasis is the concept that cells maintain their internal environment with respect to their external environment in order to remain within a certain functional range.
Physiologists use model systems at various levels of organization to study specific questions about normal and abnormal function.