Explanation

In multicellular organisms, chemical signaling can be categorized into three basic types:

• Paracrine signaling: This type of signaling involves the release of chemical signals, such as hormones or neurotransmitters, into the extracellular fluid, where they can bind to nearby cells. Examples include histamine release during an allergic reaction and neurotransmitters released by nerve cells.
• Autocrine signaling: In this type of signaling, cells release chemical signals that bind to receptors on their own surface, regulating their own behavior. Examples include the regulation of cell growth and division.
• Endocrine signaling: This type of signaling involves the release of hormones into the bloodstream, which are then transported to distant cells, where they bind to receptors and regulate various physiological processes. Examples include insulin regulating blood sugar levels and thyroid hormones regulating metabolism.