Name: how the blood-brain barrier works
Uploaded: 2025-10-23T11:47:15.000Z
Duration: 49 s
Channel: JoVE

O cérebro humano está isolado do sistema circulatório através de uma barreira protetora chamada de barreira hematoencefálica, que consiste em células endoteliais que alinham os capilares do sistema nervoso central. A barreira hematoencefálica também consiste em uma membrana basal e células neurais especializadas chamadas astrócitos, que estão em contato próximo com os capilares. Esses componentes ajudam a prevenir o cruzamento de substâncias indesejáveis.Esta barreira controla a troca química entre o sangue e o fluido intersticial no cérebro, através de diferentes tipos de proteínas que formam complexos juncionais. Geralmente, apenas compostos lipossolúveis podem se difundir através da barreira, enquanto os compostos solúveis em água cruzam via transporte ativo ou passivo.

Daneman, Richard e Alexandre Prat. "A barreira hematoencefálica." Cold Spring Harbor Perspectives in Biology 7, nº 1 (janeiro de 2015). [<a href="https://doi.org/10.1101/cshperspect.a020412" target="__blank">Fonte</a>]

Andreone, Benjamin J., Baptiste Lacoste e Chenghua Gu. "Interações neuronais e vasculares". Revisão Anual de Neurociência 38 (8 de julho de 2015): 25–46. [<a href="https://doi.org/10.1146/annurev-neuro-071714-033835" target="__blank">Fonte</a>]

a barreira hematoencefálica

The Blood-brain Barrier

<h4>Visão Geral</h4>
 
 A barreira hematoencefálica (BBB) refere-se à vasculatura especializada que fornece ao cérebro nutrientes do sangue, regulando rigorosamente o movimento de iões, moléculas, agentes patogénicos e outras substâncias. É composto por células endoteliais fortemente ligadas de um lado e projeções de astrócitos do outro. Juntas, elas constituem uma barreira semipermeável que protege o cérebro e coloca desafios únicos para a entregas terapêuticas.
 
 <h4>Componentes Celulares</h4>
 
 A BBB é composta por uma variedade de componentes celulares, incluindo células endoteliais e astrócitos. Essas células compartilham uma membrana basal comum e, juntas, regulam a passagem de componentes entre a circulação e o fluido intersticial ao redor do cérebro.
 
 O primeiro tipo de componente celular, as células endoteliais especializadas, compõem as paredes dos capilares cerebrais. Elas estão ligadas por junções intercelulares extremamente apertadas e complexas. Essas junções criam uma barreira física seletiva, prevenindo a difusão simples da maioria das substâncias, incluindo moléculas médias a grandes, como glicose e insulina.
 
 Um segundo tipo de célula, astrócitos, são um tipo de célula da glia do sistema nervoso central que influencia a função celular endotelial, o fluxo sanguíneo e o equilíbrio de iões no cérebro através da interação e estreita associação com a vasculatura cerebral. Eles fornecem uma ligação direta entre a vasculatura e os neurónios: eles estendem processos—chamados endfeet—que envolvem os vasos sanguíneos em uma extremidade enquanto fazem contacto íntimo com neurónios em sinapses na outra extremidade.
 
 <h4>Intercâmbio Químico</h4>
 
 A capacidade de uma substância atravessar a BBB e a eficiência com que essa troca ocorre depende das propriedades químicas e moleculares de cada molécula ou ião. No geral, pequenos componentes lipossolúveis, como oxigénio e dióxido de carbono, sofrem uma rápida e simples difusão através da camada endotelial. Em contraste, componentes maiores ou solúveis em água muitas vezes requerem um processo mais seletivo que pode envolver transporte passivo ou ativo através de uma célula endotelial. A troca dessas substâncias geralmente ocorre mais lentamente ou pode não ocorrer, dependendo da abundância relativa e eficiência de receptores específicos de moléculas e proteínas de transporte na superfície das células endoteliais, entre outros fatores.
 
 <h4>A BBB Protege o Cérebro</h4>
 
 A proteção neural facilitada pela BBB é fundamental para a saúde e função cerebral adequadas. A desregulação da BBB pode levar a doenças neurológicas graves, incluindo esclerose múltipla, infeção e isquémia devido a um fornecimento sanguíneo inadequado. Por outro lado, a atividade da BBB pode ser prejudicial ao tratamento de algumas doenças neurológicas, prevenindo ou reduzindo substancialmente a passagem de medicamentos neuroativos para o sistema nervoso central. Por essa razão, medicamentos com alvos neurológicos devem ser criados de forma a facilitar a passagem pela BBB.

A Barreira Hematoencefálica

Visão geral

A barreira hematoencefálica (BHE) refere-se à vasculatura especializada que fornece ao cérebro nutrientes no sangue, enquanto estritamente ...

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how the blood-brain barrier works

The blood-brain barrier is a specialized system of blood vessels that helps control what enters the brain. It delivers nutrients from the blood while tightly regulating ions, molecules, pathogens, and other substances. This semipermeable barrier protects the brain and also makes it harder to deliver some therapies.

The blood-brain barrier includes several cellular parts, especially endothelial cells and astrocytes. These cells share a common basement membrane and regulate movement between the circulation and the fluid around the brain. Specialized endothelial cells form the walls of cerebral capillaries. They are joined by very tight intercellular junctions, which create a selective physical barrier. This barrier blocks simple diffusion of most substances, including molecules as large as glucose and insulin.

Astrocytes are glial cells in the central nervous system. They influence endothelial cell function, blood flow, and ion balance in the brain. Astrocytes connect closely with the cerebral vasculature. Their processes, called endfeet, wrap around blood vessels on one end and make contact with neurons at synapses on the other. This gives them a direct link between blood vessels and nerve cells.

What crosses the barrier depends on a molecule's chemical and molecular properties. Small lipid-soluble substances, such as oxygen and carbon dioxide, move across by rapid simple diffusion. Larger or water-soluble substances usually need a more selective process. They may move through an endothelial cell by passive or active transport. In many cases, this exchange is slower, or it may not occur at all, depending on receptors and transport proteins on the endothelial surface.

The blood-brain barrier is essential for brain health and normal function. When it does not work properly, severe neurological diseases can occur, including multiple sclerosis, infection, and ischemia from poor blood supply. The barrier can also make treatment difficult because it can reduce the passage of neuroactive drugs into the central nervous system. For that reason, medicines aimed at the brain must be designed to pass through the blood-brain barrier.

How the Blood-Brain Barrier Works

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the blood-brain barrier

The blood-brain barrier is a specialized system of blood vessels that helps control what enters the brain. It delivers nutrients from the blood while tightly regulating ions, molecules, pathogens, and other substances. This semipermeable barrier protects the brain and also makes it harder to deliver some therapies. The blood-brain barrier includes several cellular parts, especially endothelial cells and astrocytes. These cells share a common basement membrane and regulate movement between the...

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key terms and concepts

Learn how the blood-brain barrier protects the brain, which cells build it, what can cross it, and why it matters for disease and drug delivery.

How the Blood-Brain Barrier Works | JoVE K12

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How the Blood-Brain Barrier Works

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