Physiology

Physiology is the scientific study of the and  which work within a.

As a of, the focus of physiology is on how s, s, , , and s carry out the  and  functions that exist in a living system.

Central to an understanding of physiological functioning is the investigation of the fundamental biophysical and biochemical phenomena, the coordinated control mechanisms, and the continuous  between cells.

The physiologic state is the condition occurring from normal body function, while the state is centered on the abnormalities that occur in animal diseases, including humans.

According to the type of investigated organisms, the field can be divided into, animal physiology (including that of ),, and.

The is awarded to those who make significant achievements in this discipline by the.

Humans
Human physiology seeks to understand the mechanisms that work to keep the alive and functioning, through scientific enquiry into the nature of mechanical, physical, and biochemical functions of humans, their organs, and the cells of which they are composed. The principal level of focus of physiology is at the level of organs and systems within systems. The endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function in animals. Homeostasis is a major aspect with regard to such interactions within plants as well as animals. The biological basis of the study of physiology, integration refers to the overlap of many functions of the systems of the human body, as well as its accompanied form. It is achieved through communication that occurs in a variety of ways, both electrical and chemical.

Changes in physiology can impact the mental functions of individuals. Examples of this would be the effects of certain medications or toxic levels of substances. Change in as a result of these substances is often used to assess the health of individuals.

Much of the foundation of knowledge in human physiology was provided by animal experimentation. Due to the frequent connection between form and function, physiology and are intrinsically linked and are studied in tandem as part of a medical curriculum.

Plants
Plant physiology is a subdiscipline of concerned with the functioning of plants. Closely related fields include, , , , genetics, , and. Fundamental processes of plant physiology include, , , s, , , , s, , , and ta function and transpiration. Absorption of water by roots, production of food in the leaves, and growth of shoots towards light are examples of plant physiology.

Cells
Although there are differences between animal, plant, and microbial cells, the basic physiological functions of cells can be divided into the processes of, , , and.

Microorganisms
Microorganisms can be found almost everywhere on Earth. Types of microorganisms include archaea, bacteria, eukaryotes, protists, fungi, and micro-plants. and in many ways, serving to, , , s and other s. They are essential tools in  as s and have been put to use in  and. They are a vital. In the microorganisms make up the  including the essential. They are the s responsible for many s and as such are the target of. Most microorganisms can reproduce rapidly, and bacteria are also able to freely exchange genes through, and , even between widely divergent species.

The classical era
The study of human physiology as a medical field originates in, at the time of (late 5th century BC). Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in China, India and elsewhere. Hippocrates incorporated his belief system called the theory of humours, which consisted of four basic substance: earth, water, air and fire. Each substance is known for having a corresponding humour: black bile, phlegm, blood and yellow bile, respectively. Hippocrates also noted some emotional connections to the four humours, which Claudius Galenus would later expand on. The critical thinking of and his emphasis on the relationship between structure and function marked the beginning of physiology in. Like Hippocrates, Aristotle took to the humoral theory of disease, which also consisted of four primary qualities in life: hot, cold, wet and dry. Claudius Galenus (c. 130–200 AD), known as of Pergamum, was the first to use experiments to probe the functions of the body. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, including the entire body. His modification of this theory better equipped doctors to make more precise diagnoses. Galen also played off of Hippocrates idea that emotions were also tied to the humours, and added the notion of temperaments: sanguine corresponds with blood; phlegmatic is tied to phlegm; yellow bile is connected to choleric; and black bile corresponds with melancholy. Galen also saw the human body consisting of three connected systems: the brain and nerves, which are responsible for thoughts and sensations; the heart and arteries, which give life; and the liver and veins, which can be attributed to nutrition and growth. Galen was also the founder of experimental physiology. And for the next 1,400 years, Galenic physiology was a powerful and influential tool in medicine.

Early modern period
(1497–1558), a French physician, introduced the term "physiology". Galen,, , , and , are credited as making important discoveries in the. in 1610s was the first to use a device to measure the rate (the pulsilogium), and a  to measure temperature.

In 1791 described the role of electricity in nerves of dissected frogs. In 1811, studied respiration in animal dissection and lesions and found the center of respiration in the. In the same year, finished work on what would later become known as the, which compared functional differences between dorsal and ventral roots of the. In 1824, described the sensory roots and produced the first evidence of the cerebellum’s role in  to complete the Bell-Magendie law.

In the 1820s, the French physiologist introduced the notion of physiological division of labor, which allowed to "compare and study living things as if they were machines created by the industry of man." Inspired in the work of, Milne-Edwards wrote that the "body of all living beings, whether animal or plant, resembles a factory ... where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual." In more differentiated organisms, the functional labor could be apportioned between different instruments or (called by him as appareils).

In 1858, studied the cause of blood coagulation and inflammation that resulted after previous injuries and surgical wounds. He later discovered and implemented s in the operating room, and as a result decreased death rate from surgery by a substantial amount.

was founded in London in 1876 as a dining club. (APS) is a nonprofit organization that was founded in 1887. The Society is, "devoted to fostering education, scientific research, and dissemination of information in the physiological sciences."

In 1891, performed research on "conditional responses" that involved dogs' saliva production in response to a bell and visual stimuli.

In the 19th century, physiological knowledge began to accumulate at a rapid rate, in particular with the 1838 appearance of the of  and. It radically stated that organisms are made up of units called cells. 's (1813–1878) further discoveries ultimately led to his concept of  (internal environment), which would later be taken up and championed as "" by American physiologist in 1929. By homeostasis, Cannon meant "the maintenance of steady states in the body and the physiological processes through which they are regulated." In other words, the body's ability to regulate its internal environment. William Beaumont was the first American to utilize the practical application of physiology.

Nineteenth century physiologists such as, , and , based on 's ideas, elaborated what came to be called "general physiology", a unified science of life based on the cell actions, later renamed in the 20th century as.

Late modern period
In the 20th century, biologists became interested in how organisms other than human beings function, eventually spawning the fields of  and. Major figures in these fields include and. Most recently, has become a distinct subdiscipline.

In 1920, won the Nobel Prize for discovering how, in capillaries, blood flow is regulated.

In 1954, and Hugh Huxley, alongside their research team, discovered the sliding filaments in, known today as the sliding filament theory.

Recently, there have been intense debates about the vitality of physiology as a discipline (Is it dead or alive?). If physiology is perhaps less visible nowadays than during the golden age of the 19th century, it is in large part because the field has given birth to some of the most active domains of today's biological sciences, such as, , and. Furthermore, physiology is still often seen as an integrative discipline, which can put together into a coherent framework data coming from various different domains.

Women in physiology
Initially, women were largely excluded from official involvement in any physiological society. The, for example, was founded in 1887 and included only men in its ranks. In 1902, the American Physiological Society elected as the first female member of the society. Hyde, a representative of the and a global advocate for gender equality in education, attempted to promote gender equality in every aspect of science and medicine.

Soon thereafter, in 1913, proposed that women be allowed to formally join, which had been founded in 1876. On 3 July 1915, six women were officially admitted:, , , , , and. The centenary of the election of women was celebrated in 2015 with the publication of the book "Women Physiologists: Centenary Celebrations And Beyond For The Physiological Society." (ISBN 978-0-9933410-0-7)

Prominent women physiologists include:
 * , along with husband, received the Nobel Prize in Physiology or Medicine in 1947 for their discovery of the -containing form of known as , as well as its function within   mechanisms for energy production. Moreover, they discovered the , also known as the Lactic acid cycle, which describes how muscle tissue converts glycogen into lactic acid via.
 * was rewarded the 1983 Nobel Prize in Physiology or Medicine for the discovery of McClintock is the only female recipient who has won an unshared Nobel Prize.
 * , along with and, received the Nobel Prize for Physiology or Medicine in 1988 for their development of drugs employed in the treatment of several major diseases, such as , some , , , and.
 * , along with, received the Nobel Prize in Physiology or Medicine in 2004 for their discovery of and the complex organization of the.
 * , along with, received the Nobel Prize in Physiology or Medicine in 2008 for their work on the identification of the (HIV), the cause of  (AIDS).
 * , along with and, was awarded the 2009 Nobel Prize for Physiology or Medicine for the discovery of the genetic composition and function of  and the enzyme called.

Subdisciplines
There are many ways to categorize the subdiscplines of physiology:
 * based on the studied:, animal physiology, , microbial physiology, viral physiology
 * based on the :, , physiology, organismal physiology, , integrative physiology
 * based on the process that causes physiological variation: physiology, ,
 * based on the ultimate goals of the research: (e.g., medical physiology),  (e.g., )