The Endocrine System Functions

The endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, whereas the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body release into the bloodstream specific chemical messengers called hormones. Hormones regulate the many and varied functions of an organism, e.g., mood, growth and development, tissue function, and metabolism, as well as sending messages and acting on them.
  Subscribe in a reader Types of signaling
The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other modes, i.e., paracrine, autocrine, and neuroendocrine signaling. Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.
A number of glands that signal each other in sequence is usually referred to as an axis, for example, the hypothalamic-pituitary-adrenal axis.
Typical endocrine glands are the pituitary, thyroid, and adrenal glands. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast, exocrine glands, such as salivary glands, sweat glands, and glands within the gastrointestinal tract, tend to be much less vascular and have ducts or a hollow lumen.
Autocrine signaling
Autocrine signaling is a form of signalling in which a cell secretes a hormone, or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cell. This can be contrasted with paracrine signaling, intracrine signalling, or classical endocrine signaling.
Paracrine signaling is a form of cell signaling in which the target cell is near ("para" = near) the signal-releasing cell.
A distinction is sometimes made between paracrine and autocrine signaling. Both affect neighboring cells, but whereas autocrine signaling occurs among the same cell, paracrine signaling affects other cells. Two neurons would be an example of a paracrine signal.
Juxtacrine signaling is a type of intercellular communication which is transmitted via oligosaccharide, lipid or protein components of a cell membrane and may affect either the emitting cell or immediately adjacent cells.
It occurs between adjacent cells that possess broad patches of closely opposed plasma membrane linked by transmembrane channels known as connexons. The gap between the cells can only usually be between 2-4nm.

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