figure 3.20 Dendrites, soma, and axon The brain’s neurons are cells that have three primary parts: (1) the main body of the cell, or the soma; (2) dendrites, which receive incoming signals from other neurons; and the neuron’s (3) axon, a long, thin projection from the cell body along which signals are sent to other neurons. The axon is surrounded by a myelin sheath, a fatty substance that increases the speed with which signals travel along the axon.