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.
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.[2] Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.
Endocrine
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
Other signaling can target the same cell.
Paracrine
Paracrine signaling is where the target cell is nearby.
Juxtacrine
Juxtacrine signals are transmitted along cell membranes via protein or lipid components integral to the membrane and are capable of affecting either the emitting cell or cells immediately adjacent.
Endocrinopathies are classified as primary, secondary, or tertiary. Primary endocrine disease inhibits the action of downstream glands. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.
Cancer can occur in endocrine glands, such as the thyroid, and hormones have been implicated in signaling distant tissues to proliferate, for example the Estrogen receptor has been shown to be involved in certain breast cancers. Endocrine, Paracrine, and autocrine signaling have all been implicated in proliferation, one of the required steps of oncogenesis.[4]
Table of endocrine glands and secreted hormones
This is a table of the glands of the endocrine system, and their secreted hormones
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