Name: glial cells and nervous system support
Uploaded: 2025-10-23T11:49:28.000Z
Duration: 1 min 4 s
Channel: JoVE

グリア細胞は神経系の支持細胞です。中枢神経系(CNS)にはさまざまなグリア細胞があります。最も大きく数が多いのがアストロサイトです。この細胞は多くの機能を持ちますが その中のひとつに血液脳関門を維持する機能があります。別の種類のオリゴデンドロサイトは より小さい細胞体で突起も少ないもので 軸索に沿ってミエリン鞘を形成します。ミクログリアは最も数が少なく小さい細胞で 食作用過程に関連しており 病原体や細胞残屑を貪食します。さらに、衛星細胞などの末梢神経系(PNS)は 神経細胞体を囲んでおり 中枢神経系(CNS)のアストロサイトのような機能を持ちます。また、シュワン細胞も同様に オリゴデンドロサイトに似た機能を持ち 末梢軸索を囲む鞘の形成を助けます。研究が進むにつれて、グリア細胞はただ神経系を接着するだけでなく それ以上の機能があるということが明確になっています。

「哺乳類の発達と病気におけるグリア」 開発(ケンブリッジ、イングランド)142、no.22(2015年11月15日):3805-9。[<a href="https://doi.org/10.1242/dev.129304" target="__blank">ソース</a>]

グリア細胞

<h4>概要</h4>
 
 グリア細胞は、神経系の2つの主要な細胞タイプのうちの1つです。グリア細胞は、中枢神経系ではアストロサイト、オリゴデンドロサイト、ミクログリア、上衣細胞、末梢神経系ではサテライト細胞やシュワン細胞を構成します。これらの細胞は、神経細胞のような電気信号によるコミュニケーションは行わないですが、神経系の機能のほぼすべての側面に貢献しています。人間の場合、グリア細胞の数は、脳内のニューロンの数とほぼ同じです。
 
 <h4>中枢神経系のグリア細胞</h4>
 
 中枢神経系(CNS)のグリアには、アストロサイト、オリゴデンドロサイト、ミクログリア、上衣細胞などがあります。アストロサイトは、最も豊富な種類のグリア細胞で、脳全体に組織化された重複しないパターンで存在し、神経細胞や毛細血管と密接に関連しています。アストロサイトは、血流や代謝プロセスの調節、シナプスのイオンやpHのホメオスタシス、血液脳関門の維持など、脳の機能に多くの役割を果たしています。 
 
 もう一つの特殊なグリア細胞であるオリゴデンドロサイトは、中枢神経系で神経軸索を取り囲むミエリン鞘を形成しています。ミエリン鞘は、神経細胞のシグナル伝達が適切に行われるために必要であり、メッセージの伝達速度を大幅に向上させます。
 
 ミクログリア（CNSのマクロファージとして知られている）は最小のグリア細胞のタイプで、病原体と破片の両方を貪食することに特化しています。ミクログリアは、感染症や毒素からCNSを保護し、発達過程でシナプスを切断します。ミクログリアはグリア細胞と考えられていますが、他のグリア細胞タイプと比較して、ユニークで別の起源を持っています。アストロサイトとオリゴデンドロサイトは放射状グリアによって作られますが、ミクログリアは卵黄嚢に由来し、胚発生の初期に胚内に移動します。 
 
 最後に、上衣細胞は繊毛のような突起を持つ立方体状の細胞で、脳室に並んでおり、脳脊髄液（CSF）を生成しています。上衣細胞は脳とCSFの間のバリアを形成し、潜在的に有害な物質をろ過しています。上衣細胞は、アストロサイトやオリゴデンドロサイトと同様に、側脳室の近くにある放射状のグリアに由来します。
 
 <h4>末梢神経系のグリア細胞</h4>
 
 末梢神経系(PNS)には、似て非なるタイプのグリア細胞が存在します。例えば、CNSのアストロサイトの機能は、PNSでは主にサテライト細胞によって実現されています。サテライト細胞は、結合している神経細胞体に構造、クッション性、栄養を提供するグリア細胞です。PNSのもう一つのグリア細胞であるシュワン細胞は、CNSのオリゴデンドロサイトと同様に、神経軸索の周りにミエリン鞘を形成して機能します。CNSのミエリン形成と同様に、PNSの軸索ミエリン形成は、電気信号の適切な伝達に必要な絶縁性と伝導性を提供します。
 
 <h4>健康と病気におけるグリアの重要性</h4>
 
 グリア細胞は、神経系の重要な保護者であり制御者です。グリアは、恒常性を維持し、日常的な脳の機能に貢献するだけでなく、神経系の損傷、感染、病気にも反応します。さらに、グリアは、神経系の胎児期に重要な機能を果たしています。さらに、グリアは、シナプスの刈り込みと呼ばれる、不要な神経細胞の結合の除去にも貢献しています。このようにグリアは脳の様々な機能に重要な役割を果たしているため、グリア細胞が欠損すると、発達障害、アルツハイマー病、パーキンソン病、多発性硬化症などの重篤で衰弱した神経疾患を引き起こす可能性があります。
 
 発達段階では、グリア細胞は神経細胞が適切に移動し、軸索を伸ばすための足場となります。その後、外傷や神経変性疾患により、再生できない神経細胞の結合が失われ、機能障害や麻痺が生じることがあります。

概要

グリア細胞は、神経系の2つの主要なタイプの細胞の1つです。グリア細胞は、アストロサイト、オリゴデンドロサイト、ミクログリア、および...

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JoVE Core

Biology

生物学

Human Biology

ヒト生物学

Nervous System

神経系

KEY TERMS AND CONCEPTS

主要用語と概念

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, non-overlapping patterns in the brain and stay close to neurons and capillaries. They help regulate blood flow, support metabolism, maintain ion and pH balance around synapses, and help maintain the blood-brain barrier.

Oligodendrocytes make the myelin sheath in the central nervous system. This sheath wraps around neuronal axons many times and acts as insulation. Myelin helps nerve signals travel correctly and much faster. Microglia are the smallest glial cells and are known as the macrophages of the CNS. They remove pathogens and debris by phagocytosis and also help prune synapses during development. Unlike other glia, microglia come from the yolk sac and enter the embryo early in development.

Ependymal cells are cube-shaped cells with cilia-like projections that line the ventricles. They produce cerebrospinal fluid, or CSF, and form a barrier between the brain and the CSF. This barrier helps filter out harmful substances. Like astrocytes and oligodendrocytes, ependymal cells come from radial glia near the lateral ventricles.

The peripheral nervous system also has glial cells. Satellite cells support the neuronal cell bodies they surround by providing structure, cushioning, and nutrients. Schwann cells do for peripheral axons what oligodendrocytes do in the CNS. They form myelin around axons and help insulation and conductivity for electrical signaling.

Glia are important for health, development, and disease. They protect the nervous system, keep internal conditions stable, and respond to injury, infection, and disease. They also help guide neuron migration and axon growth during embryonic development. Because they help remove extra neuronal connections through synaptic pruning, problems in glial cells can contribute to developmental disorders, Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and other serious conditions. Damage later in life can also lead to lost connections that are difficult or impossible to replace, which may cause impaired function or paralysis.

Glial Cells and Nervous System Support

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

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...

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 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 astrocytes, oligodendrocytes, microglia, ependymal cells, satellite cells, and Schwann cells support neurons in the CNS and PNS.

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Glial Cells and Nervous System Support

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