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

- [Narrateur] Le cerveau humain est isolé dusystème circulatoire via une barrière protectriceappelée barrière hémato-encéphalique,constituée de cellules endothélialesqui tapissent les capillaires du système nerveux central. 
La barrière hémato-encéphalique comprend égalementune membrane basale et des cellules neuronales spécialisées,appelées astrocytes, en contact étroit avec les capillaires. 
Ces composants aident à empêcherle passage de substances indésirables. 
Cette barrière contrôle les échanges chimiquesentre le sang et le liquide interstitiel dans le cerveauvia différents types de protéinesformant des complexes jonctionnels. 
En règle générale, seuls les composés liposolublespeuvent passer à travers la barrière,tandis que les composés hydrosolubles traversentvia un transport actif ou passif.

Daneman, Richard et Alexandre Prat. « La barrière hémato-encéphalique ». Cold Spring Harbor Perspectives in Biology 7, n° 1 (janvier 2015). [<a href="https://doi.org/10.1101/cshperspect.a020412 » target="__blank">Source</a>]

Andreone, Benjamin J., Baptiste Lacoste et Chenghua Gu. « Interactions neuronales et vasculaires ». Revue annuelle de neurosciences 38 (8 juillet 2015) : 25-46. [<a href="https://doi.org/10.1146/annurev-neuro-071714-033835 » target="__blank">Source</a>]

la barrière hémato-encéphalique

The Blood-brain Barrier

<h4>Aperçu</h4>
 
 La barrière hémato-encéphalique (BBB) fait référence à la vascularisation spécialisée qui fournit au cerveau des nutriments dans le sang tout en régulant strictement le mouvement des ions, des molécules, des agents pathogènes, et d’autres substances. Elle est composée de cellules endothéliales étroitement liées d’un côté et de projections d’astrocytes de l’autre. Ensemble, elles fournissent une barrière semi-perméable qui protège le cerveau et pose des défis uniques à l’apport de thérapies.
 
 <h4>Les constituants cellulaires</h4>
 
 La BBB est composée d’une variété de constituants cellulaires, y compris les cellules endothéliales et les astrocytes. Ces cellules partagent une membrane basale commune et régulent ensemble le passage des constituants entre la circulation et le fluide interstitiel entourant le cerveau.
 
 Le premier type de constituant cellulaire, les cellules endothéliales spécialisées, composent les parois des capillaires cérébraux. Elles sont reliées par des jonctions intercellulaires extrêmement serrées et complexes. Ces jonctions créent une barrière physique sélective, empêchant la simple diffusion de la plupart des substances, y compris les molécules de taille moyenne à grande telles que le glucose et l’insuline.
 
 Un second type de cellule, les astrocytes, sont un type de cellule gliale du système nerveux central qui influence la fonction de cellules endothéliales, le flux sanguin et l’équilibre des ions dans le cerveau par l’interaction et l’association étroite avec la vascularisation cérébrale. Ils fournissent un lien direct entre la vascularisation et les neurones : ils rallongent les prolongements — appelés pieds astrocytaires — qui s’enroulent autour des vaisseaux sanguins d’une extrémité tout en entrant en contact intime avec des neurones aux synapses à l’autre extrémité.
 
 <h4>L’échange chimique</h4>
 
 La faculté d’une substance à traverser la BBB et l’efficacité avec laquelle cet échange se produit dépend des propriétés chimiques et moléculaires de chaque molécule ou ion. En général, les petits constituants liposolubles, tels que l’oxygène et le dioxyde de carbone, subissent une diffusion rapide et simple à travers la couche endothéliale. En revanche, les constituants plus grands ou solubles dans l’eau nécessitent souvent un processus plus sélectif qui peut impliquer un transport passif ou actif par une cellule endothéliale. L’échange de ces substances se produit généralement plus lentement ou peut ne pas se produire du tout, selon l’abondance relative et l’efficacité des récepteurs spécifiques aux molécules et des protéines de transport à la surface des cellules endothéliales, entre autres facteurs.
 
 <h4>La BBB protège le cerveau</h4>
 
 La protection neuronale facilitée par la BBB est essentielle à la bonne santé et à la fonction du cerveau. La dysrégulation de la BBB peut entraîner des maladies neurologiques graves, y compris la sclérose en plaques, l’infection et l’ischémie en raison d’un approvisionnement insuffisant en sang. Inversement, l’activité de la BBB peut être préjudiciable au traitement de certaines maladies neurologiques en empêchant ou en réduisant considérablement le passage de médicaments pharmaceutiques neuroactifs dans le système nerveux central. Pour cette raison, les médicaments avec des cibles neurologiques doivent être conçus d’une manière qui facilite le passage à travers la BBB.

La barrière hémato-encéphalique

Aperçu

La barrière hémato-encéphalique (BHE) fait référence au système vasculaire spécialisé qui fournit au cerveau les nutriments dans le sang tout en ...

Education

Enseignement

JoVE Core

Biology

Biologie

Human Biology

Biologie humaine

Nervous System

Système nerveux

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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

what is a nervous system?

Nervous System Parts and Control

The nervous system is a network of specialized cells that keeps the body working and helps it respond to the world around it. It controls essential functions such as heart rate and breathing. It also supports movement that helps an organism escape danger. In vertebrates, the nervous system has two major parts: the central nervous system, or CNS, and the peripheral nervous system, or PNS. The CNS includes the brain, spinal cord, and retina, which is the sensory tissue of the visual system. The...

the parasympathetic nervous system

Rest and Digest: Parasympathetic Control

The parasympathetic nervous system helps the body stay calm and return to a rested state. It is one of the two major divisions of the autonomic nervous system, which controls many unconscious functions such as heart rate and digestion. Its neurons are found in the brain and the peripheral nervous system, and they send axons to muscles, organs, and glands. This system is often called the “rest and digest” system because it supports body processes that restore homeostasis. It is most active...

the sympathetic nervous system

Sympathetic Stress Response and Body Changes

The sympathetic nervous system helps the body respond to stress and danger. It is one of the two main divisions of the autonomic nervous system. When it turns on, it prepares the body for action and puts lower-priority functions, such as digestion, on hold. This response is often called the fight-or-flight system. A surprise exam can trigger it, and students may notice a tight stomach, a dry mouth, and a fast heartbeat. In a real threat, the system shifts blood away from the digestive system...

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...

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...

glial cells

Glial Cells and Nervous System Support

Glial cells support the nervous system and work alongside neurons. They are one of the two main cell types in the nervous system. Unlike neurons, glia do not send electrical signals, but they help with nearly every other part of nervous system function. In humans, glial cells are about as numerous as neurons in the brain. In the central nervous system, glia include astrocytes, oligodendrocytes, microglia, and ependymal cells. Astrocytes are the most common glial cells. They form organized,...

action potentials

How Nerve Signals Travel in Axons

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...

the resting membrane potential

How Neurons Keep a Negative Resting Charge

Neurons keep a negative resting charge across their membrane. This electrical difference, called the membrane potential, comes from how ions move and how the membrane lets them pass. In a resting neuron, the inside is typically around -70 millivolts and is more negative than the outside, so the cell is polarized. Two main factors create this resting state. First, the membrane is selectively permeable, which means most ions and molecules cannot cross the lipid bilayer without help from ion...

long-term potentiation

Synaptic Strengthening in Learning and Memory

Long-term potentiation, or LTP, is a form of synaptic strengthening in the brain. It changes the strength of chemical synapses over time between pre- and postsynaptic neurons. LTP works against long-term depression, or LTD, which weakens synapses. Together, LTP and LTD are major mechanisms behind learning and memory. LTP can happen when a presynaptic neuron fires again and again and keeps stimulating a postsynaptic neuron. This is called Hebbian LTP, based on Donald Hebb’s idea that neurons...

long-term depression

Synaptic Pruning in Long-term Depression

Long-term depression, or LTD, is a form of synaptic plasticity that weakens chemical synapses over time. It acts between presynaptic and postsynaptic neurons. LTD works in opposition to long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP are two of the main mechanisms behind learning and memory. LTD helps the brain avoid staying locked in a fully strengthened state. If synapses were always maximally strengthened, the brain would become less efficient and it would...

the synapse

How Neurons Signal at Synapses

Neurons communicate through synapses, the points where two neurons meet to pass on signals. At a synapse, the sending neuron is the presynaptic cell, and the receiving neuron is the postsynaptic cell. Most neurons can serve in both roles because they send and receive information. Electrical synapses move signals directly between cells. The presynaptic and postsynaptic cells are linked by gap junctions, which are proteins that physically connect them. This type of synapse can pass electrical...

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

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

La collection JoVE Core Biologie donne vie à la biologie à travers plus de 300 leçons vidéos animées concises et faciles à comprendre qui expliquent les concept clés de la biologie, mais aussi plus de 150 vidéos de scientifiques à l'action effectuant des expériences de recherche dans des laboratoires modernes.

myJoVE Corporation

How the Blood-Brain Barrier Works

Description

Transcript

Tags