Chromatophores are irregularly shaped, pigment-containing cells.

If the pigment is melanin, they are called melanophores.

Chromatophores are common in

Chromatophores are often used for camouflage. This picture (courtesy of the Field Museum of Natural History) shows a winter flounder resting on a checkerboard pattern.

The chromatophores of cephalopods change size (expand and contract) as a result of


A neuron is a cell specialized to conduct electrochemical impulses called nerve impulses or action potentials.

Link to a page describing these.

All neurons outside the central nervous system (and many within it) conduct impulses along hairlike cytoplasmic extensions, the nerve fibers or axons. (The diagram represents a motor neuron with most of its axon omitted.) The axons connecting your spinal cord to your foot can be as much as 1 m long (although only a few

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Excitable Cells

Excitable cells are those that can be stimulated to create a tiny electric current.

The color photo (courtesy of Julie H. Sandell and Richard H. Masland) is of a single interneuron in the retina of a rabbit. The cell has been