Neuron Cell Body and Processes

Neuron Cell Body

Main part of a neuron containing the nucleus, located in the CNS

Nuclei

Clusters of neuron cell bodies in the CNS

Ganglia

Clusters of neuron cell bodies in the PNS

Neuron Processes

Armlike extensions from the cell body; includes dendrites and axons

Tracts

Bundles of neuron processes in the CNS

Nerves

Bundles of neuron processes in the PNS

Dendrites

Short, tapering processes that convey incoming messages toward the cell body

Axon

Single process that carries nerve impulses away from the cell body

Axon Hillock

Cone-shaped area where the axon originates from the cell body

Nerve Fibers

Long axons, some over 1 meter, with terminal branches called axon terminals or boutons

Myelin Sheath

Whitish substance that insulates and increases the speed of nerve impulse transmission

Schwann Cells

Cells in the PNS that form myelin sheath around axons in a jelly roll fashion

Nodes of Ranvier

Gaps between adjacent Schwann cells in the myelin sheath

Oligodendrocytes

Cells in the CNS that form myelin sheath around multiple axons

White Matter

Brain and spinal cord regions with dense collections of myelinated fibers

Gray Matter

Regions with neuron cell bodies and nonmyelinated fibers

Multipolar Neurons

Neurons with three or more processes, including one axon and multiple dendrites; most common in the CNS

Bipolar Neurons

Neurons with two processes (one axon, one dendrite); rare and found in sensory organs

Unipolar Neurons

Neurons with a single T-like process, also called pseudounipolar; found in sensory receptors and enter the CNS

Sensory Neurons

Neurons that transmit impulses from sensory receptors toward the CNS; mostly unipolar

Motor Neurons

Neurons that carry impulses from the CNS to effectors; mostly multipolar

Interneurons

Neurons that shuttle signals through CNS pathways, mostly entirely within the CNS