Human physiology is the science of the mechanical, physical, bioelectrical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. Physiology focuses principally at the level of organs and systems. Most aspects of human physiology are closely homologous to corresponding aspects of animal physiology, and animal experimentation has provided much of the foundation of physiological knowledge. Anatomy and physiology are closely related fields of study: anatomy, the study of form, and physiology, the study of function, are intrinsically related and are studied in tandem as part of a medical curriculum.
The term "homeostasis" refers to the maintenance of overall inner resistance in the body. Homeostasis stabilizes the body by regulating the internal environment. This is required for the body to function sufficiently. The Homeostatic process is essential for the survival of each cell, tissue, and body system. Homeostasis in a general sense refers to stability, balance or equilibrium. Maintaining a stable internal environment requires constant monitoring, mostly by the brain and nervous system. The brain receives information from the body and responds appropriately through the release of various substances like neurotransmitters, catecholamines, and hormones. Individual organ physiology furthermore facilitates the maintenance of homeostasis of the whole body e.g. Blood pressure regulation: the release of renin by the kidneys allow blood pressure to be stabilized (Renin, Angiotensinogen, Aldosterone System), though the brain helps regulate blood pressure by the Pituitary releasing Anti-Diuretic Hormone (ADH). Thus, homeostasis is maintained within the body as a whole, dependent upon its parts.
Traditionally, the academic discipline of physiology views the body as a collection of interacting systems, each with its own combination of functions and purposes. Each body system contributes to the homeostasis of other systems and of the entire organism. No system of the body works in isolation, and the well-being of the person depends upon the well-being of all the interacting body systems.
The circulatory system consists of the heart and blood vessels (arteries, veins, capillaries). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen, fuel, nutrients, waste products, immune cells, and signalling molecules (i.e., hormones) from one part of the body to another. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as the spleen and bone marrow.
The integumentary system consists of the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands. The skin provides containment, structure, and protection for other organs, but it also serves as a major sensory interface with the outside world.
The reproductive system consists of the gonads and the internal and external sex organs. The reproductive system produces gametes in each sex, a mechanism for their combination, and a nurturing environment for the first 9 months of development of the offspring.
The traditional divisions by system are somewhat arbitrary. Many body parts participate in more than one system, and systems might be organized by function, by embryological origin, or other categorizations. In particular, is the "neuroendocrine system", the complex interactions of the neurological and endocrinological systems which together regulate physiology. Furthermore, many aspects of physiology are not as easily included in the traditional organ system categories.
The study of human physiology dates back to at least 420 B.C. and the time of Hippocrates, the father of medicine.1 The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece, while Claudius Galenus (c. 126-199 A.D.), known as Galen, was the first to use experiments to probe the function of the body. Galen was the founder of experimental physiology.2 The medical world moved on from Galenism only with the appearance of Andreas Vesalius and William Harvey.3
Portrait of Vesalius from his De humani corporis fabrica (1543).
Following from the Middle Ages, the Renaissance brought an increase of physiological research in the Western world that triggered the modern study of anatomy and physiology. Andreas Vesalius was an author of one of the most influential books on human anatomy, De humani corporis fabrica.4 Vesalius is often referred to as the founder of modern human anatomy.5AnatomistWilliam Harvey described the circulatory system in the 17th century,6 demonstrating the fruitful combination of close observations and careful experiments to learn about the functions of the body, which was fundamental to the development of experimental physiology. Herman Boerhaave is sometimes referred to as a father of physiology due to his exemplary teaching in Leiden and textbook Institutiones medicae (1708).citation needed
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.
In terms of the human body, the endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function. Homeostasis is a major aspect with regard to the interactions within an organism, humans included.