Cells in multicellular organisms usually communicate via chemical messengers targeted for cells that may or may not be immediately adjacent. This cell-cell communication is typically called cell signaling.
Types of cell signaling
There are two types of cell signaling -- local signaling and long distance signaling.
Local signaling occurs when cells communicate by direct contact. Plants and animals have cell junctions that directly connect the cytoplasm of adjacent cells. Thus, signaling substances may dissolve in the cytosol and pass freely between two cells.
Animal cells may also communicate through direct contact between membrane-bound molecules on a cell's surface, which occurs during a process called cell-cell recognition. This is important for embryonic development and the immune response.
In other cases, messenger molecules are secreted by the signaling cell. These local regulators travel only short distances and influence cells in their vicinity.
Ex: Growth factors, a type of local regular, stimulates nearby target cells to grow and divide. This type of local signaling is called paracrine signaling.
Chemicals called hormones are used for long-distance signaling. Hormones vary widely in molecular size and type, and usually travel via the circulatory system to target cells in other parts of the body.
- Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Benjamin Cummings, 2002. Print.