Name: how neurons send signals
Uploaded: 2025-10-23T11:49:29.000Z
Duration: 1 min 31 s
Channel: JoVE

Os neurônios são as células do sistema nervoso que transmitem sinais elétricos. Eles vêm em uma variedade de formas e tamanhos, mas geralmente têm algumas características comuns. Todos os neurônios têm um corpo celular também chamado de soma, que contém o núcleo.A maioria dos neurônios também tem dendritos e um axônio que se estendem do corpo celular. Os dendritos são muitas vezes altamente ramificados e recebem sinais de outros neurônios em junções chamadas sinapses. O axônio, por outro lado, transmite sinais para neurônios e outras células.A colina do axônio onde o corpo celular encontra o axônio, gera o potencial de ação. A principal forma de sinalização elétrica no sistema nervoso. Os axônios são frequentemente envoltos em uma bainha de mielina gordurosa feita por células de suporte chamadas gliais, que os isola, ajudando a manter o sinal elétrico à medida que é transmitido.Os nós de ranvier, lacunas na bainha de mielina, são regiões onde o potencial de ação é repetidamente regenerado ao longo do axônio. No final do axônio está o terminal contendo vesículas sinápticas cheias de moléculas de neurotransmissores. Quando um potencial de ação chega ao terminal neurotransmissores são liberados na fenda sináptica, uma região de espaço entre células em uma sinapse.Dependendo do tipo de canal, o neurotransmissor pode ajudar a transmitir o sinal para a próxima célula.

Vasile, Flora, Elena Dossi e Nathalie Rouach. "Astrócitos Humanos: Estrutura e Funções no Cérebro Saudável." Estrutura e Função Cerebral 222, nº 5 (2017): 2017–29. [<a href="https://doi.org/10.1007/s00429-017-1383-5" target="__blank">Fonte</a>]

estrutura do neurónio

<h4>Visão Geral</h4>
 
 Os neurónios são o principal tipo de célula no sistema nervoso e geram e transmitem sinais eletroquímicos. Eles comunicam principalmente uns com os outros usando neurotransmissores em junções específicas chamadas sinapses. Os neurónios existem em muitas formas que muitas vezes estão relacionadas com a sua função, mas a maioria compartilha três estruturas principais: um axónio e dendrites que se estendem de um corpo celular.
 
 <h4>Estrutura e Função dos Neurónios</h4>
 
 O corpo celular neuronal—o soma—abriga o núcleo e os organelos vitais para a função celular. Estendendo-se do corpo celular estão estruturas finas que são especializadas em receber e enviar sinais. As dendrites normalmente recebem sinais enquanto que o axónio passa os sinais para outras células, como outros neurónios ou células musculares. O ponto em que um neurónio faz uma conexão com outra célula é chamado de sinapse.
 
 Os neurónios recebem sinais principalmente em terminais pós-sinápticos, que são frequentemente localizados em espinhas—pequenos altos salientes das dendrites. Essas estruturas especializadas contêm receptores para neurotransmissores e outros sinais químicos. As dentdrites são frequentemente altamente ramificadas, permitindo que alguns neurónios recebam dezenas de milhares de sinais. Os neurónios geralmente recebem sinais nas suas dendrites, mas também podem ter sinapses em outras áreas, como no corpo celular.
 
 O sinal recebido nas sinapses percorre a dendrite até ao soma, onde a célula pode processá-lo e determinar se deve seguir com a mensagem ou não. O potencial de ação é o principal sinal elétrico gerado pelos neurónios. Ele leva a informação para a célula seguinte. É gerado pela primeira vez no cone axónico—a junção entre o soma e o axónio.
 
 Os axónios variam em comprimento, mas podem ser bastante longos. Por exemplo, alguns estendem-se desde a medula espinhal até ao pé. Axónios mais longos são geralmente envolvidos por uma camada de mielina gordurosa que isola o axónio, ajudando a manter o sinal elétrico. A camada de mielina é criada por glia—outro tipo de célula do sistema nervoso. Em axónios com mielina, o potencial de ação é regenerado em cada nó de Ranvier—lacunas repetidas na mielina—até chegar ao terminal no final do axónio, ou terminal pré-sináptico.
 
 O terminal pré-sináptico tem vesículas que contêm conjuntos de neurotransmissores. Os potenciais de ação desencadeiam as vesículas a serem submetidas à exocitose, fundindo-se à membrana celular e libertando neurotransmissores na fenda sináptica—a lacuna entre as células em uma sinapse. Diferentes neurotransmissores podem ter efeitos variados na célula pós-sináptica. Uma sinapse excitatória aumenta a probabilidade de iniciar um potencial de ação na célula pós-sináptica, enquanto que uma sinapse inibitória diminui a probabilidade de um potencial de ação.
 
 <h4>Morfologia Neuronal</h4>
 
 A forma geral dos neurónios—a sua morfologia—pode variar drasticamente e frequentemente está relacionada com a sua função. Alguns neurónios têm poucos processos dendríticos e um único axónio, outros têm árvores dendríticas muito complexas, enquanto que outros têm axónios que podem percorrer o comprimento do organismo. As diversas morfologias são frequentemente usadas para definir o tipo de neurónio. O número de sinais—conexões sinápticas—pode influenciar a forma como uma célula responde aos sinais. Portanto, a morfologia das dendrites, e o número de sinapses que contêm, é uma característica importante que pode determinar o tipo de neurónio. No sistema nervoso periférico, as dendrites também podem definir o campo receptivo de uma célula—o espaço físico no corpo ao qual são sensíveis.
 
 <h4>A Arte de Visualizar Estruturas Neuronais</h4>
 
 O anatomista Espanhol Santiago Ramon y Cajal, trabalhando no final do século XIX e início do século XX, foi pioneiro no rastreamento de neurónios individuais e forneceu informações fundamentais sobre sua natureza. Ele produziu representações impressionantes de células que ainda oferecem uma quantidade considerável de detalhes. Usando a técnica de coloração desenvolvida e nomeada em homenagem ao biólogo Italiano Camillo Golgi, ele foi capaz de traçar a estrutura de muitos tipos diferentes de células do cérebro. Ele também esboçou algumas das conexões básicas dos circuitos neuronais—redes de neurónios que são ativadas em conjunto para processar informações específicas.

Estrutura do Neurónio

Visão geral

Os neurônios são o principal tipo de célula do sistema nervoso que gera e transmite sinais eletroquímicos. Eles se comunicam principalmente com cada ...

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Neuron Structure

how neurons send signals

Neurons send signals through a clear set of structures that let them receive, process, and pass on information. They are the main cells of the nervous system and use electrochemical signals to communicate. Neurons also talk to other cells through neurotransmitters at junctions called synapses.

Most neurons share three main parts: a cell body, also called the soma, dendrites, and an axon. The soma holds the nucleus and other organelles needed for cell function. Dendrites usually receive signals, while the axon carries signals onward to other neurons or to muscle cells.

Neurons receive input mainly at postsynaptic terminals, which are often found on small bumps called spines on dendrites. These spines contain receptors for neurotransmitters and other chemical signals. Because dendrites can branch a great deal, some neurons can collect tens of thousands of inputs. Neurons can also have synapses on other parts of the cell, such as the cell body.

Signals that arrive at synapses move down the dendrite to the soma. The cell then processes the message and decides whether to pass it on. If it does, the main electrical signal, called an action potential, starts at the axon hillock, the junction between the soma and the axon.

Axons can vary in length and may be very long. Some extend from the spinal cord all the way to the foot. Longer axons are often wrapped in a fatty myelin sheath, which insulates the axon and helps keep the electrical signal going. Glia, another type of nervous system cell, make the myelin sheath.

In myelinated axons, the action potential is regenerated at each node of Ranvier, which is one of the repeated gaps in the myelin. The signal continues this way until it reaches the presynaptic terminal at the end of the axon. That terminal contains vesicles filled with neurotransmitters.

When an action potential arrives, the vesicles fuse with the cell membrane and release neurotransmitters into the synaptic cleft, the gap between cells at a synapse. Different neurotransmitters can affect the postsynaptic cell in different ways. An excitatory synapse makes an action potential more likely, while an inhibitory synapse makes it less likely.

Neuron shape, or morphology, can vary a lot and often matches function. Some neurons have few dendritic processes and one axon, while others have highly branched dendritic trees or axons that span the length of the organism. Scientists often use these shapes to help define neuron types.

The number of synaptic connections also affects how a cell responds to signals. For neurons in the peripheral nervous system, dendrites can help define the receptive field, which is the physical area of the body that the cell senses. The form of the dendrites and the number of synapses they contain are important clues about neuron function.

The study of neuron shape was advanced by Santiago Ramon y Cajal in the late 19th and early 20th century. He traced individual neurons and made detailed drawings that still show a great deal of information. Using the staining method developed by Camillo Golgi, he was able to map many cell types in the brain and sketch basic neuronal circuits, which are networks of neurons that work together to process specific information.

How Neurons Send Signals

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neuron structure

Neurons send signals through a clear set of structures that let them receive, process, and pass on information. They are the main cells of the nervous system and use electrochemical signals to communicate. Neurons also talk to other cells through neurotransmitters at junctions called synapses. Most neurons share three main parts: a cell body, also called the soma, dendrites, and an axon. The soma holds the nucleus and other organelles needed for cell function. Dendrites usually receive...

glial cells

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action potentials

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Neurons send signals through action potentials, the rapid electrical changes that move along the axon. These signals lead to neurotransmitter release at axon terminals, which passes information through the nervous system. An action potential is an all-or-none change in membrane potential, the voltage across a cell membrane. A neuron usually has a resting membrane potential of about -70 millivolts. When it receives signals from neurotransmitters or sensory input, the membrane can become more...

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the synapse

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key terms and concepts

Learn how neurons receive, process, and transmit signals through dendrites, axons, myelin, synapses, and neurotransmitters in this high school science page.

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How Neurons Send Signals

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