In complex multicellular organisms

In complex multicellular organisms - In complex...

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In complex multicellular organisms cell-cell signaling can be divided into 3 general categories depending on the distance over which the signal is transmitted: (Fig. 13.1) endocrine signaling : the signal molecule is secreted by specialized endocrine cells, carried over far distances with the circulatory system, and finally is perceived by target cells far away from the signal-producing cells. Such signaling molecules are called hormones , per definition signal molecules that act over great distances. paracrine signaling : the signal molecule acts locally on neighboring cells . The signal molecule might not even be released into the extracellular fluid by the signal-producing cell but rather expressed on its surface (direct cell-to-cell signaling). autocrine signaling : the signaling molecule acts on the signal-producing cell itself inducing it to respond. But a cell will only respond to a signal, if it is able to perceive the signal. This is accomplished via receptors which are proteins that specifically bind signal molecules. Another prerequisit for response to a signal is the ability of the activated receptor (the
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In complex multicellular organisms - In complex...

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