Classes

Image of pyramidal neurons in mouse cerebral cortex expressing green fluorescent protein. The red staining indicates GABAergic interneurons. Source PLoS Biology Structural classification Most neurons can be anatomically characterized as:

Unipolar or Pseudounipolar: dendrite and axon emerging from same process. Bipolar: single axon and single dendrite on opposite ends of the soma. Multipolar: more than two dendrites Golgi I: neurons with long-projecting axonal processes. Golgi II: neurons whose axonal process projects locally. Some unique neuronal types can be identified according to their location in the nervous system and distinct shape. Some examples are basket, Betz, medium spiny, Purkinje, pyramidal and Renshaw cells.

 Functional classification Afferent neurons convey information from tissues and organs into the central nervous system. Efferent neurons transmit signals from the central nervous system to the effector cells and are sometimes called motor neurons. Interneurons connect neurons within specific regions of the central nervous system. Afferent and efferent can also refer to neurons which convey information from one region of the brain to another.

Classification by action on other neurons

Excitatory neurons evoke excitation of their target neurons. Excitatory neurons in the brain are often glutamatergic. Spinal motoneurons use acetylcholine as their neurotransmitter. Inhibitory neurons evoke inhibition of their target neurons. Inhibitory neurons are often interneurons. The output of some brain structures (neostriatum, globus pallidus, cerebellum) are inhibitory. The primary inhibitory neurotransmitters are GABA and glycine. Modulatory neurons evoke more complex effects termed neuromodulation. These neurons use such neurotransmitters as dopamine, acetylcholine, serotonin and others. Classification by discharge patterns Neurons can be classified according to their electrophysiological characteristics:

Tonic or regular spiking. Some neurons are typically constantly (or tonically) active. Example: interneurons in neurostriatum. Phasic or bursting. Neurons that fire in bursts are called phasic. Fast spiking. Some neurons are notable for their fast firing rates, for example some types of cortical inhibitory interneurons, cells in globus pallidus. Thin-spike. Action potentials of some neurons are more narrow compared to the others. For example, interneurons in prefrontal cortex are thin-spike neurons. Classification by neurotransmitter released

Some examples are cholinergic, GABA-ergic, glutamatergic and dopaminergic neurons.

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