Physiology

Human physiology

Human physiology is the study of how the human body's systems and functions work together to maintain a stable internal environment. It includes the study of the nervous, endocrine, cardiovascular, respiratory, digestive, and urinary systems, as well as cellular and exercise physiology. Understanding human physiology is essential for diagnosing and treating health conditions and promoting overall wellbeing.

It seeks to understand the mechanisms that work to keep the human body alive and functioning,^[4] 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.^[8]

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.^[9] Change in behavior as a result of these substances is often used to assess the health of individuals.^[10][11]

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 anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum.^[12]

Subdisciplines by research objective

Comparative physiology

Involving

The study of human physiology as a medical field originates in classical Greece, at the time of Hippocrates (late 5th century BC).^[14] Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in China,^[15] India^[16] and elsewhere. Hippocrates incorporated the theory of humorism, which consisted of four basic substances: earth, water, air and fire. Each substance is known for having a corresponding humor: black bile, phlegm, blood, and yellow bile, respectively. Hippocrates also noted some emotional connections to the four humors, on which Galen would later expand. The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the humoral theory of disease, which also consisted of four primary qualities in life: hot, cold, wet and dry.^[17] Galen (c. 130–200 AD) 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.^[18] 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 humors, 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.^[18] Galen was also the founder of experimental physiology.^[19] And for the next 1,400 years, Galenic physiology was a powerful and influential tool in medicine.^[18]

Early modern period

In the 1820s, the French physiologist Henri Milne-Edwards 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 Adam Smith, 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 systems (called by him as appareils).^[23]

In 1858,

In 1891, Ivan Pavlov performed research on "conditional responses" that involved dogs' saliva production in response to a bell and visual stimuli.^[24]

In the 19th century, physiological knowledge began to accumulate at a rapid rate, in particular with the 1838 appearance of the

In 1920, August Krogh won the Nobel Prize for discovering how, in capillaries, blood flow is regulated.^[24]

In 1954, Andrew Huxley and Hugh Huxley, alongside their research team, discovered the sliding filaments in skeletal muscle, known today as the sliding filament theory.^[24]

Recently, there have been intense debates about the vitality of physiology as a discipline (Is it dead or alive?).^[34][35] If physiology is perhaps less visible nowadays than during the golden age of the 19th century,^[36] 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 neuroscience, endocrinology, and immunology.^[37] Furthermore, physiology is still often seen as an integrative discipline, which can put together into a coherent framework data coming from various different domains.^[35][38][39]

Notable physiologists

Women in physiology

Initially, women were largely excluded from official involvement in any physiological society. The

• Bodil Schmidt-Nielsen, the first woman president of the American Physiological Society in 1975.^[45]
• Carl Cori, received the Nobel Prize in Physiology or Medicine in 1947 for their discovery of the phosphate-containing form of glucose known as glycogen, as well as its function within eukaryotic metabolic mechanisms for energy production. Moreover, they discovered the Cori cycle, also known as the Lactic acid cycle,^[47] which describes how muscle tissue converts glycogen into lactic acid via lactic acid fermentation
  .
• genetic transposition. McClintock is the only female recipient who has won an unshared Nobel Prize.^[48]
• autoimmune disorders, gout, malaria, and viral herpes
  .
• Linda B. Buck,^[50] along with Richard Axel, received the Nobel Prize in Physiology or Medicine in 2004 for their discovery of odorant receptors and the complex organization of the olfactory system.
• Acquired Immunodeficiency Syndrome
  (AIDS).
• telomeres and the enzyme called telomerase
  .

References