What type of cell with a long arm - the axon?

The type of cell with a long arm known as the axon is a neuron. Neurons are specialized cells in the nervous system that transmit electrical signals, allowing for communication between different parts of the body. The axon extends from the neuron's cell body and is responsible for carrying impulses away from the cell, often over long distances to other neurons or muscles. Axons can be covered by myelin sheaths, which enhance the speed of signal transmission.