Name the signaling which requires physical contacts between the cells involved.

Cell signaling is a three-stage process that involves a cell detecting a signaling molecule, the signaling molecule binding to a receptor, and the signal triggering a cellular response.  Cell signaling can occur in different ways, including: Autocrine signaling When a cell signals itself by releasing a ligand that binds to the cell's surface. This signaling is important in development and cancer. Intracrine signaling When a chemical signal produced by a cell acts on receptors located in the cytoplasm or nucleus of the same cell. Juxtacrine signaling When signaling occurs between... Show more

Cell signaling is a three-stage process that involves a cell detecting a signaling molecule, the signaling molecule binding to a receptor, and the signal triggering a cellular response. 

Cell signaling can occur in different ways, including:
Autocrine signaling
When a cell signals itself by releasing a ligand that binds to the cell's surface. This signaling is important in development and cancer.
Intracrine signaling
When a chemical signal produced by a cell acts on receptors located in the cytoplasm or nucleus of the same cell.
Juxtacrine signaling
When signaling occurs between physically adjacent cells.
Paracrine signaling
When cells that are near one another communicate through the release of chemical messengers. This type of signaling involves cells communicating over relatively short distances. 

Cell signaling also involves G-protein–coupled receptors (GPCRs), which respond to extracellular stimuli, like hormones, by interaction with a G-protein. GPCRs are highly involved in pituicyte functions. 

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