Neuron

Ikke at forveksle med Nerve.
En stiliseret neuron.

Et neuron (fra græsk: sene, nerve), også kaldet en nervecelle, er en celletype i nervesystemet. De adskiller sig fra andre celler ved deres mange udløbere, kaldet dendritter og aksoner, og ved at være specialiseret i transmittering af signaler, dels elektrisk intraneuronalt og dels ved hjælp af transmitterstoffer interneuronalt, der virker på andre neuroners eller effektorvævenes receptorer (se for eksempel G-protein-koblede receptorer, GPCR og den motoriske endeplade). Af neurotransmittere kan nævnes serotonin, acetylkolin, dopamin, adrenalin og noradrenalin. Formålet med hjernens netværk af neuroner er kommunikation og informationsbehandling.

I 2025 blev det offentliggjort i en artikel, at én enkelt neuron fra et menneske kan representere et enkelt begreb, objekt eller menneske (enkeltindivid), uanset sammenhængen. I 2026 blev det offentliggjort i en artikel, at én enkelt neuron fra et menneske har lang større beregningskraft end et deep learning-netværk. I en anden artikel blev det offentliggjort i 2026, at én enkelt neuron fra et menneske og pattedyr er langt mere fleksible end hidtil anticiperet af videnskaben.

Opbygning

Neuroner er de centrale komponenter i hjernen og rygmarven i centralnervesystemet (CNS) samt ganglier i det perifere nervesystem (PNS). En typisk neuron består af et cellelegeme (soma), dendritter og et axon. Dendritter er tynde strukturer, der udspringer fra cellekroppen og ofte strækker sig flere hundrede mikrometer og forgrener sig flere gange. En Axon, også kaldet en nervefiber når de er myelinerede, udspringer fra cellen ved et sted kaldet axon højen og rejser op til en en meter i mennesker og endnu længere i andre arter. En neurons cellekroppe har ofte flere dendritter, men aldrig til mere end ét Axon. Neuronets lange aksoner kan være omgivet af en isolerende fedtskede kaldet myelinskeden, som har til funktion at øge signaleringshastigheden. Myelinskeden produceres og vedligeholdes i centralnervesystemet af oligodendrocytter og af Schwannske celler i det perifere nervesystem.

I de fleste tilfælde er neuroner genereret af særlige typer af stamceller. Det menes generelt, at neuroner ikke undergår celledeling, men nyere forskning hos hunde viser, at det i nogle tilfælde sker i nethinden. Astrocytter er stjerneformede gliaceller, der er også blevet observeret at blive til neuroner. Hos mennesker ophører neurogenese stort set i voksenalderen, men i to områder i hjernen, hippocampus og den olfaktoriske pære, er der beviser for generering af nye neuroner.

Kommunikation mellem neuroner

En neuron behandler og sender oplysninger gennem elektriske og kemiske signaler. Nervecellernes signaler bygger på en spændingsforskel mellem nervecellens indre og ydre, kaldet membranpotentialet. Er neuronet i hvile, kaldes spændingsforskellen for hvilemembranpotentialet. Er ændringen i membranpotentialet tilstrækkelig stor, genereres en (alt-eller-intet) elektrokemisk puls kaldet et aktionspotentiale, som bevæger sig hurtigt langs cellens axon og aktiverer synaptiske forbindelser til andre celler.

Neurontyper

Neuroner kan overordnet inddeles i projektionsneuroner Golgi type 1 med et enkelt langt akson, der kan kommunikere med andre regioner af nervesystemet, og interneuroner Golgi type 2 som kun befinder sig i en hjerneregion. Der er dog ikke skarp adskillelse mellem disse to typer.

Specialiserede neuroner omfatter: 1) sensoriske neuroner, der reagerer på berøring, lyd, lys og alle andre stimuli, der påvirker cellerne via vores sanser, som derefter sender signaler til rygmarven og hjernen som f.eks. de kemosensoriske neuroner, se lugtesansen; 2) motoriske neuroner, der modtager signaler fra hjernen og rygmarven, som bevirker muskelsammentrækninger og påvirker glandulare udgange; 3) interneuroner, der forbinder neuroner i den samme region i hjernen eller rygmarven.

Se også

Referencer

  1. ↑ Artikelomtale: March 6, 2025, Possible foundations of human intelligence observed for the first time Citat: "...A study has demonstrated how neurons in the human brain generate memories and establish narratives. Contrary to previous beliefs, individual neurons represent the concepts we learn, regardless of the context in which we encounter them. This allows humans, unlike other animals, to establish higher and more abstract relationships, which lays the foundation of human intelligence...This is the first study to observe this neuronal behavior in humans...Published in Cell Reports, the study confirms that neurons can distinguish objects or people regardless of their context, enabling the formation of higher and more abstract relationships, which constitutes the basis of human intelligence..."The basic principle of neuronal coding in humans is the opposite of what has been observed in other species, which has significant implications," notes Quian Quiroga..."Memories are stored in a much more abstract manner in humans compared to other animals. You can think of concepts or anything else in more abstract terms, independent of the context in which you learned them," explains Dr. Quian Quiroga, suggesting that this could be one of the "foundations of human intelligence." "This ability allows us to make much more abstract and complex associations and inferences than if we were forced to think of each concept within a specific, concrete context," he asserts. In other words, humans can decontextualize their memories to create more abstract thought..."
  2. ↑ Open access: Hernan G. Rey, Theofanis I. Panagiotaropoulos, Lorenzo Gutierrez, Fernando J. Chaure, Alejandro Nasimbera, Santiago Cordisco, Fabian Nishida, Antonio Valentin, Gonzalo Alarcon, Mark P. Richardson, Silvia Kochen, Rodrigo Quian Quiroga. Lack of context modulation in human single neuron responses in the medial temporal lobe. Cell Reports, 2025; 44 (1): 115218 DOI: 10.1016/j.celrep.2024.115218, backup Citat: "...Nearly all neurons (97% during encoding and 100% during recall) initially responding to a person/place do not modulate their response with context. Likewise, nearly none (<1%) of the initially non-responsive neurons show conjunctive coding, responding to particular persons/places in a particular context during the tasks. In line with these findings, taking all neurons together it is possible to decode the person/place being depicted in each story, but not the particular story. Moreover, the neurons show consistent results across encoding and recall of the stories and during passive viewing of pictures. These results suggest a context invariant, non-conjunctive coding of memories at the single-neuron level in the human hippocampus and amygdala, in contrast to what has been described in other species..."
  3. ↑ Artikelomtale: A Single Human Neuron Is Far More Powerful Than Scientists Thought. By The Hebrew University of Jerusalem July 21, 2026 Citat: "...Inside the human cortex, a single neuron may be doing far more than simply deciding whether to send a signal. New research suggests that one brain cell can carry out computations complex enough to rival the work of a deep artificial neural network...“People often think of a neuron as a simple switch that either turns on or off,” said Segev. “What we show is that a single human neuron is itself an extraordinarily sophisticated computing device.”..."
  4. ↑ July 7, 2026, Neuroscience: Dendritic morphology and synaptic nonlinearities enhance functional complexity in human cortical neurons Citat: "...we uncover a pronounced species gap: human neurons exhibit higher complexity...Human cortical pyramidal neurons are significantly more functionally complex than their rat counterparts, primarily due to differences in dendritic membrane area and branching patterns, as well as in the density and nonlinearity of NMDA-mediated synaptic receptors...From an evolutionary perspective, our results suggest that increased single-neuron complexity may coevolve with network architecture. In humans, we find that layer 2/3 pyramidal neurons exhibit higher functional complexity than neurons in other layers, in contrast to rats where layer 5 neurons dominate..."
  5. ↑ Artikelomtale: A Massive Study Reveals the Brain Is Far More Flexible Than We Thought. By The Zuckerman Institute at Columbia University August 1, 2026 Citat: "...Are neurons dedicated specialists, or can individual brain cells participate in many different processes?...as signals moved into brain regions involved in more complex processing, neurons became increasingly difficult to sort into distinct functional groups...The researchers also found that individual neurons rarely responded in exactly the same way..."
  6. ↑ Artikel: Open Access: “Rarely categorical, highly separable representations along the cortical hierarchy” by Lorenzo Posani, Shuqi Wang, Samuel P. Muscinelli, Liam Paninski and Stefano Fusi, 15 July 2026, Nature. DOI: 10.1038/s41586-026-10668-4, backup

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