Interneuron

Interneuron
An interneuron (relay neuron) forms part of a reflex arc
MeSH	Interneurons
Code	TH H2.00.06.1.00058

An interneuron (also called relay neuron, association neuron, connector neuron or local circuit neuron) is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways. Found within the central nervous system and the enteric nervous system.

Contents 1 CNS 1.1 Current list of Petilla Interneurons maintained by the NeuroLex 1.2 Spinal interneurons 1.3 Cortical interneurons 1.4 Cerebellar interneurons 2 References 3 External links

CNS

When contrasted with the peripheral nervous system (PNS), the neurons of the central nervous system (CNS), including the brain, are all interneurons. However, in the CNS, the term interneuron is used for small, locally projecting neurons (in contrast to larger projection neurons with long-distance connections). CNS interneurons are typically inhibitory, and use the neurotransmitter GABA or glycine. However, excitatory interneurons using glutamate also exist, as do interneurons releasing neuromodulators like acetylcholine.

Examples of interneurons include the homeostasis neuron and sexual arousal neuron also connecting to the brain through the association neurons. This is theorized to help focus higher attention on relevant sensory input and help block out behaviorally irrelevant or unchanging input, such as the sensation of the backs of your thighs on a chair. The neurophysiological measure short-latency intracortical inhibition (SICI) is believed to be mediated by these inhibitory interneurons. Inhibitory interneurons are also thought to play an important role in the generation of neural oscillations.^[1]

In 2008, a nomenclature for the features of GABAergic cortical interneurons was proposed, called Petilla terminology.^[2]

Current list of Petilla Interneurons maintained by the NeuroLex

http://neurolex.org/wiki/Category:Intrinsic_neuron_role

Spinal interneurons

• 1a Inhibitory Neuron: Found in Lamina VII. Responsible for inhibiting antagonist motor neuron. 1a spindle afferents activate 1a inhibitory neuron.

• 1b Inhibitory Neuron: Found in Lamina V, VI, VII. afferent or Golgi tendon organ activates it.

Cortical interneurons

• Parvalbumin-containing interneurons
• CCK-containing interneurons
• VIP-containing interneurons

Cerebellar interneurons

• Molecular layer interneurons (basket cells, stellate cells)
• Golgi cells
• Granule cells

References

External links

• Interneurons at eMedicine Dictionary

Anatomy of torso (primarily): the spinal cord (TA 14.1.02, GA 9.749) External, dorsal Posterior median sulcus · Posterolateral sulcus Grey matter/ Rexed laminae I–VI: Posterior horn I: Marginal nucleus · II: Substantia gelatinosa of Rolando · III+IV: Nucleus proprius · Spinal lamina V · Spinal lamina VI VII: Lateral horn Intermediolateral nucleus · Posterior thoracic nucleus VIII–IX: Anterior horn Interneuron · Alpha motor neuron (Onuf's nucleus) X: Other Central gelatinous substance · Gray commissure Central canal White matter somatic/ ascending (blue) Posterior/PCML: touch: Gracile · Cuneate Lateral: proprioception: Spinocerebellar (Dorsal, Ventral) · pain/temp: Spinothalamic (Lateral, Anterior) · Posterolateral (Lissauer) · Spinotectal Spinoreticular tract · Spino-olivary tract motor/ descending (red) Lateral: Corticospinal (Lateral) · Ep (Rubrospinal, Olivospinal) Anterior: Corticospinal (Anterior) · Ep (Vestibulospinal, Reticulospinal, Tectospinal) both Anterior white commissure External, ventral Anterior median fissure · Anterolateral sulcus External, general Cervical enlargement · Lumbar enlargement · Conus medullaris · Filum terminale · Cauda equina M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D)

Histology: nervous tissue (TA A14, GA 9.849, TH H2.00.06, H3.11) CNS General Grey matter · White matter (Projection fibers · Association fiber · Commissural fiber · Lemniscus · Funiculus · Fasciculus · Decussation · Commissure) · meninges Neuroglia Myelination: Oligodendrocyte Astrocyte (Radial glial cell) · Ependymal cells (Tanycyte) · Microglia Other Pyramidal · Purkinje · Granule Neuropil PNS General Posterior (Root, Ganglion, Ramus) · Anterior (Root, Ramus) · rami communicantes (Gray, White) · Autonomic ganglion (Preganglionic nerve fibers · Postganglionic nerve fibers) Connective tissues epineurium · perineurium · endoneurium · nerve fascicle Neuroglia Myelination: Schwann cell (Neurolemma, Myelin incisure, Myelin sheath gap, Internodal segment) Satellite glial cell Neurons/ nerve fibers Parts Perikaryon (Axon hillock) Axon (Axon terminals, Axoplasm, Axolemma, Neurofibril/neurofilament) Dendrite (Nissl body, Dendritic spine, Apical dendrite/Basal dendrite) Types Bipolar · Unipolar · Pseudounipolar · Multipolar · Interneuron (Renshaw) Afferent nerve fiber/ Sensory nerve GSA · GVA · SSA · SVA fibers (Ia, Ib or Golgi, II or Aβ, III or Aδ or fast pain, IV or C or slow pain) Efferent nerve fiber/ Motor nerve GSE · GVE · SVE Upper motor neuron · Lower motor neuron (α motorneuron, γ motorneuron, β motorneuron) Termination Synapse Electrical synapse/Gap junction · Chemical synapse (Synaptic vesicle, Active zone, Postsynaptic density) · Ribbon synapse · Neuromuscular junction Sensory receptors Meissner's corpuscle · Merkel nerve ending · Pacinian corpuscle · Ruffini ending · Muscle spindle · Free nerve ending · Olfactory receptor neuron · Photoreceptor cell · Hair cell · Taste bud M: CNS anat(n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp noco(m/d/e/h/v/s)/cong/tumr, sysi/epon, injr proc, drug(N1A/2AB/C/3/4/7A/B/C/D) M: PNS anat(h/r/t/c/b/l/s/a)/phys(r)/devp/prot/nttr/nttm/ntrp noco/auto/cong/tumr, sysi/epon, injr proc, drug(N1B)