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Information about Sliding Filament Mechanism

The sliding filament mechanism is a process used by muscles to contract.

Process of Movement

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Depiction of the contraction of a muscle through the overlap of thick and thin filament fibers
Myosin is a molecular motor that acts like an active ratchet. Chains of actin proteins form high tensile passive 'thin' filaments that transmit the force generated by myosin to the ends of the muscle. Myosin also forms 'thick' filaments. Each myosin 'paddles' along an actin filament repeatedly binding, ratcheting and letting go, sliding the thick filament over thin filament.
  1. Myosin heads bind to the passive actin filaments at the myosin binding sites.
  2. Upon strong binding, myosin and actin undergo an isomerization (myosin rotates at the myosin-actin interface) extending an extensible region in the neck of the myosin head.
  3. Shortening occurs when the extensible region pulls the filaments across each other (like the shortening of a spring). Myosin remains attached to the actin.
  4. The binding of ATP allows myosin to detach from actin. While detached, ATP hydrolysis occurs "recharging" the myosin head. If the actin binding sites are still available, myosin can bind actin again.
  5. The collective bending of numerous myosin heads (all in the same direction), combine to move the actin filament relative to the myosin filament. This results in muscle contraction.
All real muscle cells are composed of a number of actin and myosin filaments in series. The basic unit is called the sarcomere. It consists of a central bidirectional thick filament flanked by two actin filaments, orientated in opposite directions. When each end of the myosin thick filament ratchets along the actin filament with which it overlaps, the two actin filaments are drawn closer together. Thus, the ends of the sarcomere are drawn in and the sarcomere shortens. Sarcomeres are connected together by so-called 'Z lines', which anchor the ends of actin filaments in such a way that the filaments on each side of the Z line point in opposite directions. By this means, sarcomeres are arranged in series. When a muscle fiber contracts, all sarcomeres contract simultaneously so that force is transmitted to the fiber ends.

Pre-Process of Movement

If the process of movement were to continue constantly, all muscles would constantly be contracted. Therefore, the body needs a way to control the ability of myosin to bind to the actin. This is accomplished by the introduction of calcium into the cytoplasm of the muscle cell.
  1. When the muscle does not need to contract (is in a resting state), thin strands of a protein called tropomyosin are wrapped around the actin filaments, blocking the myosin binding sites. This inhibits the myosin from binding to actin, and therefore causing a chain of events leading to muscle contraction.
  2. Molecules called troponin are attached to the tropomyosin.
  3. When calcium is introduced into the muscle cell (fiber), calcium ions bind to troponin molecules.
  4. Calcium binding changes the shape of troponin, causing tropomyosin to be moved as well, therefore causing the myosin binding sites on the actin to be exposed.
  5. Myosin binds to the now-exposed binding sites, and muscles contract via the sliding-filament mechanism.
Nerve impulses affect the way in which calcium bonds to the troponin.

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Histology: muscle tissue
skeletal muscle/generalepimysium, fascicle, perimysium, endomysium, muscle fiber (intrafusal, extrafusal), myofibril sarcomere (a, i, and h bands; z and m lines), myofilaments (thin filament/actin, thick filament/myosin, elastic filament/titin, nebulin), tropomyosin, troponin (T, C, I) costamere (dystrophin, α,β-dystrobrevin, syncoilin, synemin/desmuslin, dysbindin, sarcoglycan, dystroglycan, sarcospan), desmin neuromuscular junction, motor unit, muscle spindle, excitation-contraction coupling, sliding filament mechanism myoblast, satellite cell, sarcoplasm, sarcolemma, sarcoplasmic reticulum, T-tubule
cardiac musclemyocardium, intercalated disc, nebulette
smooth musclecalmodulin, vascular smooth muscle
MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten or remain the same.
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Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.

Structure and Function

Domains

Most myosin molecules are composed of both a head and a tail domain.
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A ratchet may refer to:
  • ratchet (device), a mechanical device for controlling rotational motion
  • socket wrench, a tool that makes use of the above mechanical device
  • ratchet (instrument), a music instrument

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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.

Structure and Function

Domains

Most myosin molecules are composed of both a head and a tail domain.
..... Click the link for more information.
Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions — in this context collectively called ligands, or more specifically, protein ligands — form a chemical bond.
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Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism.
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A sarcomere is the basic unit of a muscle's cross-striated myofibril. Sarcomeres are multi-protein complexes composed of three different filament systems.
  • The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by Titin

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A sarcomere is the basic unit of a muscle's cross-striated myofibril. Sarcomeres are multi-protein complexes composed of three different filament systems.
  • The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by Titin

..... Click the link for more information.
Cytoplasm is a gelatinous, semi-transparent fluid that fills most cells. Eukaryotic cells contain a nucleus that is kept separate from the cytoplasm by a double membrane layer. The cytoplasm has three major elements; the cytosol, organelles and inclusions.
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Please help recruit one or [ improve this article] yourself. See the talk page for details.
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Troponin is a complex of three proteins that is integral to muscle contraction in skeletal and cardiac muscle, but not smooth muscle. Troponin is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue.
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Histology (from the Greek ἱστός) is the study of tissue sectioned as a thin slice, using a microtome. It can be described as microscopic anatomy.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
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Epimysium is a layer of connective tissue which ensheaths the entire muscle. It is composed of dense irregular connective tissue. It is continuous with fascia and other connective tissue wrappings of muscle including the endomysium, and perimysium.
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In anatomy, a fascicle is a bundle of skeletal muscle fibers surrounded by connective tissue.

Specialized muscle fibers in the heart which transmit electrical impulses from the Atrioventricular Node (AV Node) to the Purkinje Fibers are fascicles, also referred to as bundle
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Perimysium is a sheath of connective tissue which groups individual muscle fibers ( anywhere between 10 to 100 or more) into bundles or fascicles

See also

  • Endomysium

External links

  • Histology at cytochemistry.

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The endomysium, literally meaning within the muscle, is a layer of connective tissue that ensheaths a muscle fiber and is composed mostly from reticular fibers. It also contains capillaries, nerves and lymphatics.
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muscle fiber, also spelled muscle fibre (see spelling differences), also technically known as a myocyte, is a single cell of a muscle. Muscle fibers contain many myofibrils, the contractile unit of muscles.
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Intrafusal fibers are muscle fibers that comprise the muscle spindle. These fibers are walled off from the rest of the muscle by a collagen sheath. This sheath has a spindle or "fusiform" shape, hence the name "intrafusal.
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Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons.

They are motor neurons and generate tension, mechanical work and allow for movement by contracting.
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Myofibrils (obsolete term: sarcostyles) are cylindrical organelles, found within muscle cells. They are bundles of actomyosin filaments that run from one end of the cell to the other and are attached to the cell surface membrane at each end.
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A sarcomere is the basic unit of a muscle's cross-striated myofibril. Sarcomeres are multi-protein complexes composed of three different filament systems.
  • The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by Titin

..... Click the link for more information.
The filaments of myofibrils constructed from proteins, myofilaments, consist of 2 types, thick and thin. Thin filaments consist primarily of the protein actin; thick filaments consist primarily of the protein myosin.
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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
..... Click the link for more information.
Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.

Structure and Function

Domains

Most myosin molecules are composed of both a head and a tail domain.
..... Click the link for more information.
Not to be confused with Tintin.


Titin, also known as connectin[1] (UniProt name: Q10466_HUMAN; accession number: Q10466), is a protein that is important in the contraction of striated muscle tissues.
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