In physiology, a stimulus (plural stimuli) is a detectable change in the internal or external environment. When a stimulus is applied to a sensory receptor, it elicits or influences a reflex via stimulus transduction. A stimulus is often the first component of a homeostatic control system. When a sensory nerve and a motor nerve communicate with each other, it is called a nerve stimulus.
Any of your five senses will accommodate to a particular stimulus. The stimulus–response model describes how statistical units such as receptor cells response to their effective stimulus.
Physiology (from Greek φύσις, physis, "nature, origin"; and -λογία, -logia) is the study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided between plant physiology and animal physiology but the principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about the physiology of yeast cells may also apply to human cells.
The field of animal physiology extends the tools and methods of human physiology to non-human animal species. Plant physiology also borrows techniques from both fields. Its scope of subjects is at least as diverse as the tree of life itself. Due to this diversity of subjects, research in animal physiology tends to concentrate on understanding how physiological traits changed throughout the evolutionary history of animals. Other major branches of scientific study that have grown out of physiology research include biochemistry, biophysics, paleobiology, biomechanics, and pharmacology.
Physiology can trace its roots back more than two millennia to classical antiquity, to the Greek and Indian medical traditions. Human physiology dates back to at least 420 B.C. and the time of Hippocrates, the father of medicine. 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. The ancient Indian books of Ayurveda, the Sushruta Samhita and Charaka Samhita, also had descriptions on human anatomy and physiology. The medical world moved on from Galenism only with the appearance of Andreas Vesalius and William Harvey.
During the Middle Ages, the ancient Greek and Indian medical traditions were further developed by Muslim physicians, most notably Avicenna (980-1037), who introduced experimentation and quantification into the study of physiology in The Canon of Medicine. Many of the ancient physiological doctrines were eventually discredited by Ibn al-Nafis (1213-1288), who was the first physician to correctly describe the anatomy of the heart, the coronary circulation, the structure of the lungs, and the pulmonary circulation, for which he is considered the father of circulatory physiology. He was also the first to describe the relationship between the lungs and the aeration of the blood, the cause of pulsation, and an early concept of capillary circulation.
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.
logy is a suffix in English, found in words originally adapted from Greek words ending in -λογία (-logia). The earliest English examples were anglicizations of the French -logie, which was in turn inherited from the Latin -logia.
It has two main senses in English:
In words of the type theology, the suffix is derived originally from -λογ- (-log-) (a variant of -λεγ-, -leg-), from the Greek verb λέγειν (legein, "to speak"). The suffix has the sense of "the character or department of one who speaks or treats of [a certain subject]", or more succinctly, "the study of [a certain subject]".
 -logy versus -ology
In English names for fields of study, the suffix -logy is most frequently found preceded by the vowel o so the word ends in -ology. In traditional English grammar, the -o- in -ology is considered part of the suffix -logy. This is because the -o- is not part of the suffix in the original Greek names for fields of study: In these Greek words, the root is always a noun and -o- is the combining vowel for all declensions of Greek nouns. However, when new names for fields of study have been coined in modern English, the formations ending in -logy almost invariably follow the Greek model by adding an -o-, even though there is no grammatical necessity in English. There are at least 22 exceptions: analogy, dekalogy, disanalogy, genealogy, genethlialogy, herbalogy (a variant of herbology), idealogy, mammalogy, mineralogy, paralogy, pentalogy, petralogy (a variant of petrology), tetralogy; elogy; antilogy, festilogy, trilogy; palillogy, pyroballogy; dyslogy; eulogy; and brachylogy.Linguists sometimes jokingly refer to haplology as haplogy (subjecting the word haplology to haplology).
 Additional usage as a suffix
Per metonymy, words ending in -logy are sometimes used to describe a subject rather than the study of it (e.g. technology). This usage is particularly widespread in medicine; for example, pathology is often used simply to refer to "the study of a disease" but to refer to "the disease" itself (e.g. "We haven't found the pathology yet").
Books, journals and treatises about a subject also often bear the name of this subject (e. g. Ecology (journal)).
When appended to other English words, the suffix can also be used humorously to create nonce words (e.g. beerology as "the study of beer", Wikiology as "the study of Wikipedia"). As with other classical compounds, adding the suffix to a initial word-stem derived from Greek or Latin may be used to lend grandeur or the impression of scientific rigor to humble pursuits, as in cosmetology ("the study of beauty treatment") or cynology ("the study of dog training").
In grammar, a suffix (also postfix, ending) is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs.
Some examples from English:
 Inflectional suffixes
Inflection changes grammatical properties of a word within its syntactic category. In the example:
the suffix -ed inflects the root-word clear to indicate past tense.
Some inflectional suffixes in present day English:
 Derivational suffixes
In the example:
the suffix -ish modifies the root-word clear, changing its meaning to "clear, but not very clear".
Some derivational suffixes in present day English:
 See also
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