How Cells Communicate

1) Direct Intercellular Signaling – requires that cells be in direct contact (adjacent) to each other. Signals are passed through “cell junctions” from the cytosol of one cell to the cytosol of the next cell.

Advantages:  quickest transport of signals.

Disadvantages: not all signaling molecules can readily diffuse from one cell to another.

Example: Movement of cilia on the cells in the lungs that help remove particles from the lungs by “sweeping” the particles away.

2) Contact-Dependent Signaling –  requires that cells be in contact so that contact is made between a membrane-bound signaling molecule on on cell and a receptor on the surface of another cell.

Advantages: allows communication via molecules that are too large to diffuse through cell walls.

Disadvantages: the signaling molecule and receptor have to touch each other “just right” in order for the proper contact and communication to be made.

Example: As nerve cells grow, they bump into each other and recognize the signal that they have just bumped into a cell of a the same type.

3) Autocrine Signaling – cells release signaling molecules that bind to themselves and other nearby cells of the same type.

Advantages: allows behavior of all cells of the same type in a certain area to be affected quickly.

Disadvantages: Affects only one type of cell within a limited area from the signal cell.

Example: Allows cells to recognize how dense their numbers are. If there are many cells of the same type in the same place, the concentration of autocrine signals will be high.

4) Paracrine Signaling – cells release signaling molecules that bind to nearby cells of a different type.

Advantages: provides a way for cells of different types to communicate within a small area.

Disadvantages: only works within a limited area from the signal cell.

Example: Synaptic signaling allows neurotransmitters to cross a synapse and bind to receptors in target cells. A couple examples of neurotransmitters are dopamine and seratonin.

5) Endocrine Signaling – cells release signals that travel long distances to affect their target cells.

Advantages: allows communication to occur over long distances.

Disadvantages: the slowest form of cell communication.

Example: Hormones are secreted into the bloodstream and affect cells in other parts of the body. Signaling molecules can also be released as a gas; for example, plants give of ethylene which accelerate the ripening of fruit.