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

İnsan beyni, dolaşım sisteminden koruyucu bir bariyerle yalıtılmıştır.
 Kan beyin bariyeri merkezi sinir sisteminin kılcal damarlarını kaplayan endotelyal hücrelerden oluşur.
 Kan beyin bariyeri ayrıca bir bazal membrandan ve kılcal damarlarla yakın temasta olan astrosit denen özel sinir hücrelerinden oluşur.
Bu elemanlar istenmeyen maddelerin geçişini engeller.
 Bu bariyer kanla beyindeki doku içi sıvı arasındaki kimyasal alışverişi, kavşak kompleksler oluşturan farklı protein türleriyle kontrol eder.
 Genellikle bariyeri sadece yağda çözünen bileşikler geçebilirken, suda çözünen bileşikler aktif vaya pasif transportla geçer.

Daneman, Richard ve Alexandre Prat. "Kan-Beyin Bariyeri." Cold Spring Harbor Biyolojide Perspektifler 7, no. 1 (Ocak 2015). [<a href="https://doi.org/10.1101/cshperspect.a020412" target="__blank">Kaynak</a>]

Andreone, Benjamin J., Baptiste Lacoste ve Chenghua Gu. "Nöronal ve Vasküler Etkileşimler." Sinirbilimin Yıllık İncelemesi 38 (8 Temmuz 2015): 25–46. [<a href="https://doi.org/10.1146/annurev-neuro-071714-033835" target="__blank">Kaynak</a>]

kan-beyin bariyeri

The Blood-brain Barrier

<h4>Genel Bakış</h4>

Kan-beyin bariyeri (KBB), beyne kandaki besin maddelerini sağlarken, iyonların, moleküllerin, patojenlerin ve diğer maddelerin hareketini sıkı bir şekilde düzenleyen özel vasküler yapıyı ifade eder. Bir tarafta sıkıca bağlanmış endotel hücreleri ve diğer tarafta astrosit projeksiyonlarından oluşur. Birlikte, beyni koruyan ve terapötiklerin uygulanmasında farklı zorluklar yaratan yarı geçirgen bir bariyer sağlarlar.

<h4>Hücresel Bileşenler</h4>

KBB, endotel hücreleri ve astrositler de dahil olmak üzere çeşitli hücresel bileşenlerden oluşur. Bu hücreler ortak bir bazal membranı paylaşır ve birlikte dolaşım ile beyni çevreleyen interstisyel sıvı arasındaki bileşenlerin geçişini düzenler.

İlk tip hücresel bileşen olan özel endotel hücreleri, serebral kılcal damarların duvarlarını oluşturur. Son derece sıkı ve karmaşık hücreler arası kavşaklarla bağlanırlar. Bu kavşaklar, glikoz ve insülin gibi ortalama ve büyük boyutlu moleküller de dahil olmak üzere çoğu maddenin basit difüzyonunu önleyen seçici bir fiziksel bariyer oluşturur.

İkinci bir hücre tipi olan astrositler, beyindeki endotel hücre fonksiyonunu, kan akışını ve iyon dengesini etkileşim ve serebral vasküler yapı ile yakın ilişki yoluyla etkileyen merkezi sinir sisteminin bir glial hücresidir. Vasküler yapı ve nöronlar arasında doğrudan bir bağlantı sağlarlar: bir uçta kan damarlarının etrafını sararken ve diğer uçta sinapslardaki nöronlarla yakın temas kurarlar.

<h4>Kimyasal Değişim</h4>

Bir maddenin KBB'ni geçme yeteneği ve bu değişimin gerçekleştiği verimlilik, her molekülün veya iyonun kimyasal ve moleküler özelliklerine bağlıdır. Genel olarak, oksijen ve karbondioksit gibi küçük lipitte çözünen bileşenler, endotel tabakasından hızlı şekilde, basit difüzyona uğrar. Buna karşılık, daha büyük veya suda çözünür bileşenler genellikle bir endotel hücresi boyunca pasif veya aktif taşınmayı içerebilecek daha seçici bir işlem gerektirir. Bu maddelerin değişimi, diğer faktörlerin yanı sıra, endotel hücrelerinin yüzeyindeki moleküle özgü reseptörlerin ve taşıma proteinlerinin göreceli bolluğuna ve verimliliğine bağlı olarak genellikle daha yavaş gerçekleşir veya hiç gerçekleşmeyebilir.

<h4>KBB Beyni Korur</h4>

KBB tarafından kolaylaştırılan nöral koruma, uygun beyin sağlığı ve işlevi için kritik öneme sahiptir. KBB'nin düzensizliği, yetersiz kan dolaşımına bağlı olarak multipl skleroz, enfeksiyon ve iskemi gibi ciddi nörolojik hastalıklara yol açabilir. Tersine, KBB'nin aktivitesi, nöroaktif farmasötik ilaçların merkezi sinir sistemine geçişini önleyerek veya önemli ölçüde azaltarak bazı nörolojik hastalıkların tedavisinde zararlı olabilir. Bu nedenle, nörolojik hedefleri olan ilaçlar, KBB’nden geçişi kolaylaştıracak şekilde tasarlanmalıdır.

Kan-beyin Bariyeri

Genel bakış

Kan-beyin bariyeri (BBB), beyne kandaki besinleri sağlayan özel damar sistemini ifade ederken, kesinlikle ...

Education

JoVE Core

Biology

Biyoloji

Human Biology

İnsan Biyolojisi

Nervous System

Sinir Sistemi

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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

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JoVE Core serisi, biyolojinin ana konseptlerini açıklayan 300 adet kısa ve kolay anlaşılabilir olan video dersleriyle ve günümüz laboratuvarlarında yürütülen gerçek araştırmaları gösteren 150'den fazla \"bilim insanları iş başında\" videolarıyla biyolojiye hayat vermektedir.

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How the Blood-Brain Barrier Works

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