Nerve cell (neuron), illustration. Neurons are responsible for passing information around the central nervous system (CNS) and from the CNS to the rest of the body. Each nerve cell comprises a body (upper centre) surrounded by numerous extensions called dendrites. Dendrites collect information from other nerve cells or from sensory cells. Each neuron also has one process called an axon (down centre and detail at right), which passes information to other nerve cells, or to effector cells such as muscle fibres. The axon appears segmented as it is surrounded by a myelin sheath (blue) that contains gaps, called nodes of Ranvier. The myelin insulates the axon, allowing signals to be transmitted more quickly. At bottom right is the detail of a synapse, or junction, between two neurons. As the electrical signal reaches the presynaptic end of a neuron it triggers the release of neurotransmitters across the gap, or synaptic cleft, between the two cells. The neurotransmitters bind to receptors on the postsynaptic membrane, changing the membrane's excitability and triggering an electrical impulse.