From ancient theories to molecular laboratory techniques, physiological research has shaped understanding of our internal milieu, how it communicates and how it keeps us alive.
Contents of this article:
What is physiology?
Physiology is, in a sense, the study of life. It asks questions about the internal workings of organisms and how they interact with the world around them. Physiology tests how organs and systems within the body work, how they speak to each other and how they combine their efforts to make conditions favorable for survival.
Physiology covers a multitude of disciplines within human biology and beyond.
Human physiology, specifically, is often separated into subcategories, these disciplines have an impressive breadth of scope.
Physiologists can focus on anything from microscopic organelles in cell physiology up to more cumbersome topics, such as ecophysiology, which looks at whole organisms and how they adapt to environments.
The most relevant arm of physiological research for Medical News Today is applied human physiology; this field investigates biological systems at the level of the cell, organ, system, anatomy, organism and everywhere in between.
In this article, we will visit some of the subsections of physiology, developing a brief overview of the huge subject that is physiology. Firstly, though, a highly abbreviated history of physiology.
A brief history of physiology
Hippocrates is considered by many to be the "father of medicine."
The study of physiology traces its roots back to ancient India and Egypt. As a medical discipline, it goes back at least as far as the time of Hippocrates, the famous "father of medicine" - around 420 BC.
Hippocrates coined the theory of the four humors, stating that the body contains four distinct bodily fluids: black bile, phlegm, blood and yellow bile. Any disturbance in their ratios, the theory goes, causes ill health.
Claudius Galenus (c.130-200 AD), also known as Galen, modified Hippocrates' theory and was the first to use experimentation to derive information abut the systems of the body. He is widely referred to as the founder of experimental physiology.
It was Jean Fernel (1497-1558), a French physician, who first introduced the term "physiology," from Ancient Greek, meaning "study of nature, origins." Fernel was also the first to describe the spinal canal (the space in the spine where the spinal cord passes through). He has a crater on the moon named after him for his troubles; it is called Fernelius.
Another leap forward in physiological knowledge came with the publication of William Harvey's book titled An Anatomical Dissertation Upon the Movement of the Heart and Blood in Animals in 1628.1
Harvey was the first to describe systemic circulation and blood's journey through the brain and body, propelled by the heart.
Perhaps surprisingly, much medical practice was based on the four humors until well into the 1800s (bloodletting, for instance). In 1838, a shift in thought occurred when the cell theory of Matthias Schleiden and Theodor Schwann arrived on the scene, positing that the body was made up of minute individual cells.
From here on in, the field of physiology opened up and advancement was swift:
- Joseph Lister, 1858: initially studied coagulation and inflammation following injury, he went on to discover and utilize lifesaving antiseptics2
- Ivan Pavlov, 1891: conditioned physiological responses in dogs
- August Krogh, 1910: won the Nobel Prize for discovering how blood flow is regulated in capillaries
- Andrew Huxley and Alan Hodgkin, 1952: discovered the ionic mechanism by which nerve impulses are transmitted
- Andrew Huxley and Hugh Huxley, 1954: made advances in the study of muscles with the discovery of sliding filaments in skeletal muscle.
On the next page, we look at some of the biological systems covered by physiology and other related topics.