From Wikipedia, the free encyclopedia
An interneuron (also called relay neuron,association neuron or bipolar neuron) is a term used to describe a neuron which has two different common meanings.
In the peripheral nervous system, an interneuron is a neuron that communicates only to other neurons. Interneurons are the neurons that provide connections between sensory and motor neurons, as well as between themselves. Contrast to sensory neurons or motor neurons, which respectively provide input from and output to the rest of the body.
Interneurons are found in the grey matter. One type of peripheral interneuron is the Renshaw cell.
According to the PNS definition, the neurons of the central nervous system, including the brain, are all interneurons. However, in the CNS, the term interneurons is also used for the general group of small, locally projecting neurons of the central nervous system. These neurons are typically inhibitory, and use the neurotransmitter GABA. However, excitatory interneurons also exist.
One example of interneurons are inhibitory interneurons in the neocortex which selectively inhibit sections of the thalamus based on synaptic input both from other parts of the neocortex and from the thalamus itself. This is theorized to help focus higher attention on relevant sensory input and help block out behavioraly irrelevant or unchanging input, such as the sensation of the backs of your thighs on a chair. A human brain contains about 100 billion interneurons.
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Anatomy of torso (primarily): the spinal cord |
| epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater, denticulate ligaments
conus medullaris, cauda equina, filum terminale, cervical enlargement, lumbar enlargement, anterior median fissure
spinal nerve: dorsal root, dorsal root ganglion, dorsal ramus, ventral root, ventral ramus, sympathetic trunk, ramus communicans (gray, white)
gray matter: central canal, substantia gelatinosa of Rolando, reticular formation, substantia gelatinosa centralis, interneuron, anterior horn, lateral horn, posterior horn (column of Clarke, dorsal spinocerebellar tract)
white matter: anterior funiculus: descending (anterior corticospinal tract, vestibulospinal fasciculus, tectospinal tract), ascending (anterior spinothalamic tract, anterior proper fasciculus)
lateral funiculus: descending (lateral corticospinal tract, rubrospinal tract, olivospinal tract), ascending (dorsal spinocerebellar tract, ventral spinocerebellar tract, spinothalamic tract, lateral spinothalamic tract, anterior spinothalamic tract, spinotectal tract, posterolateral tract, lateral proper fasciculus, medial longitudinal fasciculus
posterior funiculus: fasciculus gracilis, fasciculus cuneatus, posterior proper fasciculus
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Histology: nervous tissue |
Neurons (gray matter): soma, axon (axon hillock, axoplasm, axolemma, neurofibril/neurofilament), dendrite (Nissl body, dendritic spine)
types (bipolar, pseudounipolar, multipolar, pyramidal, Purkinje, granule)
Afferent nerve/Sensory nerve/Sensory neuron (GSA, GVA, SSA, SVA, Type Ia sensory fiber), Efferent nerve/Motor nerve/Motor neuron (GSE, GVE, SVE) Alpha motor neuron, Gamma motoneurons, Upper motor neuron, Lower motor neuron), Interneuron (Renshaw)
Synapses: neuropil, synaptic vesicle, neuromuscular junction, electrical synapse
Sensory receptors: Free nerve ending, Meissner's corpuscle, Merkel nerve ending, Muscle spindle, Pacinian corpuscle, Ruffini ending, Olfactory receptor neuron, Photoreceptor cell, Hair cell, Taste bud
Glial cells: astrocyte, ependymal cells, microglia, radial glia
Myelination (white matter): Schwann cell, oligodendrocyte, nodes of Ranvier, internode, Schmidt-Lanterman incisures, neurolemma
Related connective tissues: epineurium, perineurium, endoneurium, nerve fascicle, meninges
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