A brief introduction to physiology: History, biological systems, and branches

A brief introduction to physiology: History, biological systems, and branches

Physiology is the science of physical activity within living beings. It is a biology sub-section, covering a variety of subjects that include organs, anatomy, cells, biological compounds and how they all work to make life possible.

From ancient theories to molecular laboratory techniques, our knowledge of the components of our body, how they interact and how they keep us alive has been influenced by physiological research.

Merrian-Webster defines physiology as:

‘[A] branch of biology dealing with the roles and activities of life or of living matter (such as organs , tissues or cells) and the physical and chemical phenomena concerned.’

Important facts about physiology

Here are some key points about physiology. More detail and supporting information is in the main article.

  • Physiology can be considered a study of the functions and processes that create life.
  • The study of physiology can be traced back to at least 420 BC.
  • The study of physiology is split into many disciplines covering topics as different as exercise, evolution, and defense.

What is physiology?

Physiology covers a multitude of disciplines within human biology and beyond.
Physiology covers a multitude of disciplines within human biology and beyond.

In a way , the study of physiology is the study of life. It asks questions about the organisms’ internal roles, and how they communicate with the environment around them.

Physiology measures how organs and processes function within the body, how they interact and how they coordinate their efforts to establish optimal conditions for survival.

Specifically , human physiology is also divided into subcategories; these subjects cover a large amount of knowledge.

Researchers in the field will concentrate on anything ranging from microscopic organelles in cell physiology to wider subjects such as ecophysiology, which looks at entire species, and how they respond to conditions.

Applied human physiology is the most important branch of physiological science to Nccmed; this field examines biological processes at cell, organ, system, anatomy, body, and anywhere in between.

We’ll visit some of the physiology subsections in this post, providing a brief overview of this huge topic. First we’re going to run through a brief physiology history.


Hippocrates is considered by many to be the “father of medicine.”
Hippocrates is considered by many to be the “father of medicine.”

Physiology studies trace back its origins to ancient India and Egypt.

It goes back at least as far as the time of Hippocrates, the famed “father of medicine,” as a medical discipline-around 420 BC.

Hippocrates invented the four-humor theory, arguing that the body contains four distinct body fluids: black bile, phlegm, blood, and yellow bile. As theory goes, any disturbance in their ratios causes ill health.

The theory of Hippocrates was updated by Claudius Galenus (c.130-200 AD), also known as Galen, and was the first to use experiments to derive information about the body systems. He’s widely called the father of experimental physiology.

It was Jean Fernel (1497-1558), a French doctor who invented the word “physiology” from Ancient Greek for the first time , meaning “nature study, roots.”

Fernel was also the first to identify the spinal canal (the area in the spine through which the spinal cord goes). For his contributions, he has a crater on the moon named after him-it ‘s called Fernelius.

Another leap forward in physiological knowledge came in 1628 when William Harvey ‘s book, An An Anatomical Dissertation On the Movement of the Heart and Blood in Animals, was published.

Harvey was the first to identify the systemic circulation and the heart-fueled flow of blood through the brain and body.

Perhaps unexpectedly, until well into the 1800s (for example, bloodletting) a lot of medical practice had been based on the four humors. In 1838, when the cell theory of Matthias Schleiden and Theodor Schwann arrived on the scene, a change of thought occurred, theorizing that the body consisted of tiny individual cells.

From here on, the physiology area opened up, and rapid progress was made:

  • Joseph Lister, 1858 – initially studied coagulation and inflammation following injury, he went on to discover and utilize lifesaving antiseptics.
  • 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.

Biological systems

The major systems covered in the study of human physiology are as follows:

  • Circulatory system – including the heart, the blood vessels, properties of the blood, and how circulation works in sickness and health.
  • Digestive/excretory system – charting the movement of solids from the mouth to the anus; this includes study of the spleen, liver, and pancreas, the conversion of food into fuel and its final exit from the body.
  • Endocrine system – the study of endocrine hormones that carry signals throughout the organism, helping it to respond in concert. The principal endocrine glands – the pituitary, thyroid, adrenals, pancreas, parathyroids, and gonads – are a major focus, but nearly all organs release endocrine hormones.
  • Immune system – the body’s natural defense system is comprised of white blood cells, the thymus, and lymph systems. A complex array of receptors and molecules combine to protect the host from attacks by pathogens. Molecules such as antibodies and cytokines feature heavily.
  • Integumentary system – the skin, hair, nails, sweat glands, and sebaceous glands (secreting an oily or waxy substance).
  • Musculoskeletal system – the skeleton and muscles, tendons, ligaments, and cartilage. Bone marrow – where red blood cells are made – and how bones store calcium and phosphate are included.
  • Nervous system – the central nervous system (brain and spinal cord) and the peripheral nervous system. Study of the nervous system includes research into the senses, memory, emotion, movement, and thought.
  • Renal/urinary system – including the kidneys, ureters, bladder, and urethra, this system removes water from the blood, produces urine, and carries away waste.
  • Reproductive system – consisting of the gonads and the sex organs. Study of this system also includes investigating the way a fetus is created and nurtured for 9 months.
  • Respiratory system – consisting of the nose, nasopharynx, trachea, and lungs. This system brings in oxygen and expels carbon dioxide and water.


Defense physiology investigates nature’s natural defensive reactions.
Defense physiology investigates nature’s natural defensive reactions.

  • Cell physiology – studying the way cells work and interact; cell physiology mostly concentrates on membrane transport and neuron transmission.
  • Systems physiology – this focuses on the computational and mathematical modeling of complex biological systems. It tries to describe the way individual cells or components of a system converge to respond as a whole. They often investigate metabolic networks and cell signaling.
  • Evolutionary physiology – studying the way systems, or parts of systems, have adapted and changed over multiple generations. Research topics cover a lot of ground including the role of behavior in evolution, sexual selection, and physiological changes in relation to geographic variation.
  • Defense physiology – changes that occur as a reaction to a potential threat, such as preparation for the fight-or-flight response.
  • Exercise physiology – as the name suggests, this is the study of the physiology of physical exercise. This includes research into bioenergetics, biochemistry, cardiopulmonary function, biomechanics, hematology, skeletal muscle physiology, neuroendocrine function, and nervous system function.

The above topics are only a small subset of the physiologies available. The physiological area is as critical as it is vast.

Physiology or anatomy?

Anatomy is directly connected to physiology. Anatomy relates to the study of body parts structure, but physiology focuses on how those parts function and how they relate to one another.