`color{green}(★)` The `color{violet}("neural system")` provides a point-to-point rapid coordination `color{violet}("among organs.")`

`color{green}(★)` The `color{violet}("neural coordination")` is fast but short-lived.

`color{green}(★)` As the `color{violet}("nerve fibres")` do not innervate all `color{violet}("cells of the body")` and the `color{violet}("cellular functions")` need to be continuously regulated; a special kind of coordination and regulation has to be provided.

`color{green}(★)` This function is carried out by `color{violet}("hormones.")`

`color{green}(★)` The `color{violet}("neural system")` and the `color{violet}("endocrine system")` jointly coordinate and regulate the `color{violet}("physiological functions")` in the body.

`color{green}(★)` `color{violet}("Endocrine glands lack ducts")` and are hence, called `color{violet}("ductless glands.")`

`color{green}(★)` Their secretions are called `color{violet}("hormones.")`

`color{green}(★)` The classical definition of `color{violet}("hormone")` as a chemical produced by `color{violet}("endocrine glands")` and released into the blood and transported to a distantly located target `color{violet}("organ")` has current scientific definition as follows:

`color{green}(★)` `color{brown}("Hormones are non-nutrient")` `color{brown}("chemicals which act as intercellular messengers")` `color{brown}("and are produced in trace amounts.")`

`color{green}(★)` The new definition covers a number of new `color{violet}("molecules")` in addition to the `color{violet}("hormones")` secreted by the `color{violet}("organised endocrine glands")`.

`color{green}(★)` Invertebrates possess very simple `color{violet}("endocrine systems")` with few `color{violet}("hormones")` whereas a large number of chemicals act as `color{violet}("hormones")` and provide coordination in the vertebrates.

`color{green}(★)` The `color{violet}("human endocrine system")` is described here.

`color{green}(★)` The `color{violet}("endocrine glands")` and `color{violet}("hormone")` producing diffused `color{violet}("tissues/cells")` located in different parts of our body constitute the `color{violet}("endocrine system.")`

`color{green}(★)` `color{violet}("Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus")` and `color{violet}("gonads")` (testis in males and ovary in females) are the `color{violet}("organized endocrine")` bodies in our body.

`color{green}(★)` In addition to these, some `color{violet}("other organs")`, e.g., `color{violet}("gastrointestinal tract, liver, kidney, heart")` also produce `color{violet}("hormones.")`

`color{green}(★)` A brief account of the structure and functions of all `color{violet}("major endocrine glands and hypothalamus")` of the human body is given in the following sections.