Monday, November 17, 2008

intercellular communication

How do heart muscle cells synchronize their beat? How do the cells lining our windpipe synchronize the movement of their cilia? The answer my friend is – through rapid intercellular communication.

Neighboring cells maintain rapid communication lines with each other so they can act as a single unit and not as uncoordinated separate units. In animal cells the rapid communication lines (actually pipes) are called gap junctions while in plant cells they are called plasmodesmata.

Gap junctions are pipe-like structures that connect adjacent animal cells. Unlike a pipe however which is made up of one rounded piece, gap junctions consist of 6 pieces that can change orientation and therefore open or close the opening of the pipe.

In the heart for example, only one part, the pacemaker, needs to receive the activation information but the whole heart responds as an integrated beating unit. This is possible through the opening of gap junctions between adjacent cells which then rapidly spread the information received. The same process allows for the synchronized beating of the cilia in respiratory cells as they move substances from one end of the windpipe to the other end. The peristaltic movement of the digestive tube is also synchronized through the same rapid communication across gap junctions of smooth muscle cells.

Because of their cell walls, plant cells cannot move in any synchronized manner. However, through their plasmodesmata which are small channels not covered by cell walls, the cytoplasm of adjacent cells can communicate with each other and move substances between them. This way, parts of the plant can function as one metabolic unit.

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