Name: calcium control in muscle contraction
Uploaded: 2025-10-23T11:47:01.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.14

SC.912.L.14.17

Cross-bridge Cycle

細い繊維と 太い繊維の重なりが大きくなると 筋肉が収縮し，筋厚が小さくなります。分子レベルでは、ミオシンの球状頭部領域に 結合したATPがADPに 加水分解され，ミオシン頭部が アクチンに結合して架橋を形成する 高エネルギー状態に変換されることで収縮が起こっています。ADPの放出はミオシン頭部を 低エネルギー状態に戻し，アクチンをサルコメアの中心へと動かします。新しいATP分子がミオシン頭部に結合すると，アクチンから解離します。このミオシン頭部が次にアクチンに結合するときは，z線に近い部分で起こります。この結合過程は、2つの調整タンパク質，トロポミオシンおよびトロポニン，そして筋小胞体に貯蔵され，放出される カルシウムの濃度によって 制御されます。トロポミオシンはアクチン上のミオシン結合部位を覆い、トロポミオンは結合可能ならカルシウムに結合し、トロポミオシンを アクチン上のミオシン結合部位から遠ざけます。この動きでは，クロスブリッジが形成され、筋肉が収縮します。カルシウムとATPが筋肉繊維に存在しなくなるまで、このサイクルが続きます。

Guellich, Aziz, Elisa Negroni, Valérie Decostre, Alexandre Demoule, and Catherine Coirault. "Altered Cross-Bridge Properties in Skeletal Muscle Dystrophies." Frontiers in Physiology 5 (2014年10月14日).[<a href="https://doi.org/10.3389/fphys.2014.00393" target="__blank">ソース</a>]

Debold, Edward P. "Recent Insights into Muscle Fatigue at the Cross-Bridge Level." Frontiers in Physiology 3 (2012年6月1日).[<a href="https://doi.org/10.3389/fphys.2012.00151" target="__blank">ソース</a>]

ラル、ジャックA.「骨格筋を横紋にするものは何ですか?Discoveries in the Endosarcomeric and Exosarcomeric Cytoskeleton." Advances in Physiology Education 42, no. 4 (2018年11月15日): 672–84.[<a href="https://doi.org/10.1152/advan.00152.2018" target="__blank">ソース</a>]

クロスブリッジ・サイクル

筋肉が収縮すると、細いフィラメントと太いフィラメントの重なりが大きくなり、ATPというエネルギーを使って筋肉の収縮単位であるサルコメア（Sarcomere）の長さが短くなります。分子レベルでは、ATPの結合と加水分解、ミオシンによるアクチンの移動など、周期的で多段階のプロセスが行われています。 
 
 ミオシンの頭部に付着したATPが加水分解されてADPになると、ミオシンはアクチンと結合した高エネルギー状態に移行し、クロスブリッジを形成します。ADPが放出されると、ミオシン頭部は低エネルギー状態になり、アクチンをサルコメアの中心に向かって移動させます。新しいATP分子が結合すると、ミオシンはアクチンから解離します。このATPが加水分解されると、ミオシン頭部はアクチンに結合しますが、今度はアクチンの端に近い部分に結合します。制御タンパク質であるトロポニンとトロポミオシン、そしてカルシウムが協力して、ミオシンとアクチンの相互作用を制御します。トロポニンがカルシウムと結合すると、トロポミオシンはアクチンのミオシン結合部位から遠ざかり、ミオシンとアクチンが相互に作用して筋収縮が起こります。
 
 <h4>カルシウム</h4>
 
 筋収縮の調節因子であるカルシウムの濃度は、筋線維の中で非常に細かくコントロールされています。筋線維は運動ニューロンと密接に接しています。運動ニューロンの活動電位により、神経伝達物質であるアセチルコリンが筋線維の近くで放出されます。これにより、筋細胞に活動電位（脱分極）が発生し、細胞膜に沿って、横管（T字管）と呼ばれる細胞膜の浸食部を通って運ばれます。
 
 T字管は筋肉の奥深くにあり、小胞体（SR）と呼ばれる特殊な小胞体器官に隣接しています。SRに蓄えられたカルシウムは、脱分極に応じて電位依存性イオンチャネル（局所的な電荷に応じて開閉するイオンチャネル）が開くことで放出され、カルシウムイオンが細胞質に入り込み、筋肉が収縮します。
 
 運動ニューロンからのシグナル伝達が停止すると、カルシウムがSRに戻され、細胞質内のカルシウムレベルが低下し、次の収縮に備えてSRのカルシウム貯蔵量が補充されるため、筋肉の弛緩が始まります。
 
 <h4>筋肉の退化</h4>
 
 健康な筋肉は収縮できますが、病気の筋肉はその能力を失っていることが多いです。重症筋無力症のような病気では、運動ニューロンが筋肉を刺激することができず、その結果、筋肉が萎縮し、筋肉量が減少します。また、筋萎縮性側索硬化症（ALS）では、運動ニューロンが変性し、同様に筋肉が変性・萎縮していきます。

筋肉が収縮すると、細いフィラメントと太いフィラメントの重なりが増加し、サルコメアの長さが短くなります。

Education

JoVE Core

Biology

生物学

Human Biology

ヒト生物学

Musculoskeletal System

筋骨格系

KEY TERMS AND CONCEPTS

主要用語と概念

calcium control in muscle contraction

Calcium control in muscle contraction depends on ATP, motor neurons, and the sliding action of actin and myosin. As a muscle contracts, the thin and thick filaments overlap more, and the sarcomere, which is the contractile unit of the muscle, becomes shorter. This process uses energy from ATP and happens in a repeating cycle at the molecular level.

Myosin drives the movement of actin through a cross-bridge cycle. When ATP attached to the myosin head is hydrolyzed to ADP, myosin shifts into a high-energy state and binds actin. This forms a cross-bridge. When ADP is released, the myosin head moves to a lower-energy state and pulls actin toward the center of the sarcomere. A new ATP molecule then binds to myosin and causes it to detach from actin. After that ATP is hydrolyzed, myosin can bind again, this time to a new site on actin closer to the end of the sarcomere.

Troponin, tropomyosin, and calcium regulate this interaction. When troponin binds calcium, tropomyosin moves away from the myosin-binding site on actin. That shift lets myosin and actin interact, and muscle contraction can occur. Calcium concentration in muscle fibers is tightly controlled so this switch can happen at the right time.

Motor neurons start the process by signaling nearby muscle fibers. Their action potentials trigger release of the neurotransmitter acetylcholine near the muscle cell. This produces an action potential, or depolarization, in the muscle cell membrane. The signal travels along the plasma membrane and through T-tubules, which are inward folds of the membrane that carry the signal deep into the muscle. T-tubules sit next to the sarcoplasmic reticulum, or SR, a specialized endoplasmic reticulum that stores calcium.

When depolarization reaches the SR, voltage-gated ion channels open and release calcium into the cytoplasm. The rise in calcium allows the muscle to contract. When signaling from the motor neuron stops, relaxation begins. Calcium is pumped back into the SR, which lowers calcium in the cytoplasm and restores the SR calcium supply for the next contraction.

Healthy muscle can contract, but diseased muscle may lose that ability. Myasthenia gravis can prevent motor neuron stimulation of muscle, which can lead to muscle atrophy and a decrease in muscle mass. Amyotrophic lateral sclerosis, or ALS, also called Lou Gehrig's disease, causes motor neurons to degenerate. That loss of motor neurons can likewise lead to muscle degeneration and atrophy.

Calcium Control in Muscle Contraction

what is the skeletal system?

Human Skeleton: Bones, Cells, and Disease

The human skeleton is a living framework made of 206 bones in adults. Bones connect with cartilage, tendons, and ligaments. This system gives the body support, protects organs, and helps with movement and locomotion. The skeleton has two main parts: the axial skeleton and the appendicular skeleton. The axial skeleton has 80 bones and includes the skull, the vertebral column, and the rib cage. The cranium, or upper skull, has eight bones that enclose the brain, while the lower part of the skull...

bone structure

Inside a Long Bone

Inside a long bone, osseous tissue is organized into two main types: cortical bone and cancellous bone. A femur is a clear example of this structure. The bone also includes outer coverings and inner spaces that support growth, repair, and blood cell production. Cortical bone, also called compact bone, forms the dense outer layer along the diaphysis, or shaft. It is covered by the periosteum, a membrane with connective tissue, capillaries, and nerves. Beneath the cortical layer is the medullary...

joints

Types of Joints in the Human Body

Joints are the places where adjacent bones connect. They are also called articulations or articular surfaces. Joints help the body move and stay stable. Joints can be classified by structure or by function. Structural classification depends on the material that forms the joint and whether there is a space between the bones. By structure, joints are fibrous, cartilaginous, or synovial. Fibrous joints are connected by fibrous tissue and have no cavity between the bones. Because of this, they do...

bone remodeling

How Hormones Control Bone Turnover

Bone turnover is a continuous process in which old bone is broken down and new bone is built. Osteoclasts carry out bone resorption, and osteoblasts carry out bone formation. In adults, this balanced cycle helps maintain bone mass and calcium homeostasis. Mechanical stress can also stimulate turnover as part of normal maintenance and repair. Parathyroid hormone, or PTH, helps control blood calcium levels by increasing bone resorption when calcium is low. It is released from the parathyroid...

skeletal muscle anatomy

Muscle Fibers, Tendons, and Contraction

Skeletal muscle moves the body by pulling on bones through tendons. Tendons are the connective tissue that attaches skeletal muscle to bones. When skeletal muscles contract, they create voluntary movement. Skeletal muscle is wrapped in layers of connective tissue. The outer layer is the epimysium, which helps protect the muscle. Beneath it, the perimysium surrounds and groups fasciculi, which are bundles of skeletal muscle cells called myocytes. These cells are also called skeletal muscle...

classification of skeletal muscle fibers

Skeletal Muscle Fiber Speed and Energy

Skeletal muscle fibers can be grouped by how fast they contract and how they make ATP, the energy cells use for movement. These differences also shape their physical features. Most human muscles contain all three fiber types, but in different amounts. Slow oxidative fibers, also called slow-twitch fibers, appear red because they have many capillaries and high levels of myoglobin, an oxygen-storing protein. They also contain more mitochondria, which make ATP through oxidative phosphorylation,...

muscle contraction

Nerve Signals That Trigger Muscle Contraction

Nerve signals trigger muscle contraction in both skeletal and smooth muscle, but the two muscle types use different control systems. In skeletal muscle, the signal begins at the motor end plate, which is the synapse between a motor neuron and a muscle fiber. In smooth muscle, contraction is controlled by the autonomic nervous system and happens without conscious control. In skeletal muscle, motor nerve terminals release acetylcholine. This neurotransmitter binds to receptors on the sarcolemma,...

cross-bridge cycle

Calcium control in muscle contraction depends on ATP, motor neurons, and the sliding action of actin and myosin. As a muscle contracts, the thin and thick filaments overlap more, and the sarcomere, which is the contractile unit of the muscle, becomes shorter. This process uses energy from ATP and happens in a repeating cycle at the molecular level. Myosin drives the movement of actin through a cross-bridge cycle. When ATP attached to the myosin head is hydrolyzed to ADP, myosin shifts into a...

motor units

How Motor Units Control Muscle Movement

Motor units control skeletal muscle movement. A motor unit includes one efferent motor neuron, which carries signals away from the central nervous system, and all of the muscle fibers it innervates. A single motor neuron can connect with multiple muscle fibers, but each muscle fiber is innervated by only one motor neuron. Lower motor neurons are the efferent neurons that control skeletal muscle, the most abundant type of muscle in the body. Their cell bodies are found in the spinal cord or...

the spinal cord

Spinal Cord Structure and Dermatomes

The spinal cord is the main nerve pathway of the central nervous system. It carries sensory signals from the body to the brain and motor signals from the brain to the body. It begins at the foramen magnum, the opening at the base of the skull, and extends to the level of the first or second lumbar vertebra. In cross-section, the spinal cord is cylindrical and contains both gray matter and white matter. The central canal lies in the middle and is a remnant of the lumen of the primitive neural...

nociception

Pain Signaling and Inflammation

Pain signaling begins when the body detects a harmful stimulus. Sharp objects, open flames, and corrosive chemicals can trigger this response. Sensory receptors called nociceptors, which sit on nerve endings, detect these noxious stimuli and use ion channels to turn them into electrical signals. Those electrical signals travel through sensory neurons to the brain, where they are experienced as pain. This warning system helps an organism avoid damage and stay safe. Pain is therefore an...

key terms and concepts

Learn how calcium, troponin, tropomyosin, and ATP control muscle contraction, from motor neuron signaling to relaxation and muscle degeneration.

Calcium Control in Muscle Contraction | 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

JoVE Core シリーズは、生物学の重要な概念を説明する 300 を超える簡潔でわかりやすいアニメーション ビデオ レッスンに加え、今日の研究室で行われる実際の研究実験を示す 150 以上の科学者の活動ビデオを通じて、生物学に命を吹き込みます。

SC.912.L.14.18

myJoVE Corporation

What are Cells?

Cells are the smallest and basic units of life, whether it is a single cell that forms the entire organism, e.g., in a bacterium or trillions of them, ...

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Animal and Plant Cell Structure

Animal and plant cells not only differ in their structure, function, and mode of nutrition but also in how they reproduce, specialize, and organize into ...

Eukaryotic Evolution

The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the ...

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Chemistry of the Cell

The cell is chemically composed of water, organic molecules and inorganic ions.
Water
The polarity of the water molecule and its resulting hydrogen ...

Describe the scientific theory of cells (cell theory) and relate the history of its discovery to the process of science.

SC.912.L.14.1

Cell Size

Cell sizes vary widely among and within organisms. Bacterial cells range between 1-10 micrometers (&#x3BC;m)and are considerably smaller than most ...

Eukaryotic Compartmentalization

One of the distinguishing features of eukaryotic cells is that they contain membrane-bound organelles, such as the nucleus and mitochondria, that carry ...

Prokaryotic Cells

Prokaryotes are small unicellular organisms that include the domains&#x2014;Archaea and Bacteria. Bacteria include many common organisms, such as ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

Endoplasmic Reticulum

Endoplasmic ReticulumThe endoplasmic reticulum (ER) is an extensive network of membranous sacs and tubules in eukaryotic cells, continuous with the outer ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Golgi Apparatus

As they leave the Endoplasmic Reticulum (ER), properly folded and assembled proteins are selectively packaged into vesicles. These vesicles are ...

Microtubules

There are three types of cytoskeletal structures in eukaryotic cells&#x2014;microfilaments, intermediate filaments, and microtubules. With a diameter of ...

Peroxisomes

Peroxisomes and mitochondria are two important oxygen-utilizing organelles in eukaryotic cells. Mitochondria carry out cellular respiration&#x2014;the ...

Gap Junctions

Multicellular organisms employ a variety of ways for cells to communicate with each other. Gap junctions are specialized proteins that form pores between ...

The Extracellular Matrix

In order to maintain tissue organization, many animal cells are surrounded by structural molecules that make up the extracellular matrix (ECM). Together, ...

Tissues

Cells with similar structure and function are grouped into tissues. A group of tissues with a specialized function is called an organ. There are four main ...

Plant Cell Wall

The plant cell wall gives plant cells shape, support, and protection. As a cell matures, its cell wall specializes according to the cell type. For ...

Plasmodesmata

The organs in a multicellular organism&#x2019;s body are made up of tissues formed by cells. To work together cohesively, cells must communicate. One way ...

What are Membranes?

A key characteristic of life is the ability to separate the external environment from the internal space. To do this, cells have evolved semi-permeable ...

Membrane Fluidity

Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are ...

Fluid Mosaic Model

The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of ...

What is an Electrochemical Gradient?

Adenosine triphosphate, or ATP, is considered the primary energy source in cells. However, energy can also be stored in the electrochemical gradient of an ...

Diffusion

Diffusion is the passive movement of substances down their concentration gradients&#x2014;requiring no expenditure of cellular energy. Substances, such as ...

Osmosis

Approximately 60% to 95% of the weight of living organisms is attributed to water. Therefore, maintaining appropriate water balance within cells is of ...

Tonicity in Animals

The tonicity of a solution determines if a cell gains or loses water in that solution. The tonicity depends on the permeability of the cell membrane for ...

Tonicity in Plants

Tonicity describes the capacity of a cell to lose or gain water. It depends on the quantity of solute that does not penetrate the membrane. Tonicity ...

Introduction to Membrane Proteins

The cell membrane, or plasma membrane, is an ever-changing landscape. It is described as a fluid mosaic where various macromolecules are embedded in the ...

Facilitated Transport

The chemical and physical properties of plasma membranes cause them to be selectively permeable. Since plasma membranes have both hydrophobic and ...

Primary Active Transport

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or ...

Secondary Active Transport

One example of how cells use the energy contained in electrochemical gradients is demonstrated by glucose transport into cells. The ion vital to this ...

Receptor-mediated Endocytosis

Overview

Receptor-mediated endocytosis is a process through which bulk amounts of specific molecules can be imported into a cell after binding to cell ...

Pinocytosis

Cells use energy-requiring bulk transport mechanisms to transfer large particles, or large amounts of small particles, into or out of the cell. The cells ...

Phagocytosis

Cells pull particles inward and engulf them in spherical vesicles in an energy-requiring process called endocytosis. Phagocytosis (&#x201C;cellular ...

Exocytosis

Exocytosis is used to release material from cells. Like other bulk transport mechanisms, exocytosis requires energy.

While endocytosis takes particles ...

Relate structure to function for the components of plant and animal cells. Explain the role of cell membranes as a highly selective barrier (passive and active transport).

SC.912.L.14.2

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Compare and contrast the general structures of plant and animal cells. Compare and contrast the general structures of prokaryotic and eukaryotic cells.

SC.912.L.14.3

Overview of Microscopy Techniques

The early pioneers of microscopy opened a window into the invisible world of microorganisms. In 1830, Joseph Jackson Lister created an essentially modern ...

Introduction to Light Microscopy

The light microscope is an instrument used by researchers in many different fields to magnify specimens to as much as a thousand times their original ...

Overview of Electron Microscopy

The wavelengths of visible light ultimately limit the maximum theoretical resolution of images created by light microscopes. Most light microscopes can ...

phase-contrast-and-differential-interference-contrast-microscopy

Phase Contrast and Differential Interference Contrast Microscopy

Phase-Contrast Microscopes
In-phase-contrast microscopes, interference between light directly passing through a cell and light refracted by cellular ...

Confocal Fluorescence Microscopy

Confocal microscopy is an advanced microscopic technique. The prime advantage of the confocal microscope over other microscopy techniques is its ability ...

Introduction to Fluorescence Microscopy

Fluorescence microscopy is a very powerful analytical tool that combines the magnifying properties of light microscopy with visualization of fluorescence. ...

Super-resolution Fluorescence Microscopy

Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread ...

Compare and contrast structure and function of various types of microscopes.

SC.912.L.14.4

comparing-mitochondrial-chloroplast-and-prokaryotic-genomes

Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes

The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new ...

the-tree-of-life-bacteria-archaea-eukaryotes

The Tree of Life - Bacteria, Archaea, Eukaryotes

The &#8220;tree of life&#8221; describes the evolution of life and the evolutionary relationships between organisms. The root of the tree is the common ...

The Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor specialized organelles called chloroplasts to carry out photosynthesis. They ...

Explain the evidence supporting the scientific theory of the origin of eukaryotic cells (endosymbiosis).

SC.912.L.14.5

An Overview of Genetics and Disease

Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from ...

Factors Affecting Illness

When a person&#39;s physical, emotional, intellectual, social development or spiritual functioning is compromised, this deviation from a healthy normal ...

Gene-Environment Interactions

Gene expression is influenced by environmental factors such as radiation, temperature, behavior, nutrition, and stress.
The range of reaction suggests ...

Dimensions of Health and Illness

The factors influencing the health-illness continuum can be internal or external and may or may not be under conscious control. They are related to the ...

Factors Affecting the Risk of Infection

The hosts&#39; susceptibility to infection depends on several factors. The integrity of the skin and mucous membranes helps protect the body against ...

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

Heritability

Heritability measures the genetic influence on traits or physical characteristics such as height or eye color.
Heritability can vary depending on the ...

Infection

When a pathogen enters the body and reproduces, it can cause an infection, damage body cells, and cause illness symptoms that eventually lead to disease. ...

models-of-health-promotion-and-illness-prevention-ii

Models of Health Promotion and Illness Prevention II

The person&#39;s health status fluctuates continually, varying from being in good health to becoming ill and returning to being healthy. To understand the ...

background-and-environment-affect-phenotype

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

Inheritance

Gregor Mendel&#39;s principles of inheritance demonstrated how traits are transmitted from parents to offspring and are controlled by distinct units known ...

Explain the significance of genetic factors, environmental factors, and pathogenic agents to health from the perspectives of both individual and public health.

SC.912.L.14.6

A. Cells have characteristic structures and functions that make them distinctive.

B. Processes in a cell can be classified broadly as growth, maintenance, reproduction, and homeostasis.

C. Life can be organized in a functional and structural hierarchy ranging from cells to the biosphere.

D. Most multicellular organisms are composed of organ systems whose structures reflect their particular function.

Calcium Control in Muscle Contraction

Description

Transcript

Tags

More videos by Standards