Myocytes

Information about Myocytes

A simplified, global view of a neuromuscular junction:
1. Axon
2. Neuromuscular junction
3. Muscle fiber
4. Myofibril

A top-down view of skeletal muscle

A 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. Muscle fibres are very long; a single fibre can reach a length of 30cm.

Muscle fibres can be grouped according to what kind of tissue they are found in -- skeletal muscle, smooth muscle, and cardiac muscle. The muscle cells of heart muscle tissue are called cardiomyocytes.

Skeletal muscle fibers

Skeletal muscle fibers can be further divided into two basic types, type I (slow-twitch fibers) and type II (fast-twitch fibers). Type II is further divided, as follows:

type	Type I	Type IIa	Type IIb
Description	slow oxidative (SO) fibers	fast oxidative-glycolytic (FOG)	fast-twitch glycolytic fibers
myoglobin	high	medium	low
mitochondria	many	moderate	few
fatigues	slowly	moderate speed	fast
color	red	red	white
diameter	narrow	medium	wide

Type I

Type I muscle fibers (slow-oxidative fibers)use primarily cellular respiration and, as a result, they have relatively high endurance.

To support their high-oxidative metabolism, these muscle fibers typically have lots of mitochondria and myoglobin, and thus appear red (what is typically termed "dark" meat in poultry.)

Type I muscle fibers are typically found in muscles of animals that require endurance, such as chicken leg muscles or the wing muscles of migrating birds (e.g., geese).

Type II

Type II muscle fibers use primarily anaerobic metabolism and have relatively low endurance. These muscle fibers are typically used during tasks requiring short bursts of strength, such as sprints or weightlifting. Type II muscle fibers cannot sustain contractions for significant lengths of time, and are typically found in the white meat (e.g., the breast) of chicken.

There are two sub-classes of type II muscle fibers, type IIa (Fast-Oxidative) and IIb (Fast-Glycolytic).

Type IIa (fast-oxidative) fibers also appear red, due to their high content of myoglobin and mitochondria.
Type IIb (fast-glycolytic) are the fastest firing and most powerful, twitching in upwards of 120 times per second, are the fiber type of choice to a power lifter. They also tire the fastest. These fibers appear white histologically, due to their low oxidative demand, manifested by the lack of myoglobulin and mitochondria (relative to the Type I and Type IIa fibers)

Other terminology

Most sources use the I/IIa/IIb division described above. However, this distinction is much more clear in other animals (such as chickens) than they are in humans, where the muscle tissue usually contains combinations of different kinds of fibers in varying proportions.

Some terms used to describe this blending include:

"Type III" or "Intermediate fast-twitch fibers" are a cross between Type I and Type IIb. They can utilize both aerobic and anaerobic pathways for energy metabolism.
"Type IIc" fibers are created from a fusion of satellite cells to the corrupted Type IIb, so long as the cortisone hormone is inhibited, and offer the attributes of both Type IIa and Type IIb.

External links

http://www.coachr.org/fiber.htm - Article at coachr.org xplaining muscle fibers, especially in relation to training.
Physiology at MCG 2/2ch6/2ch6obj
Duke Orthopedics muscle_fiber_types

• • [ e] Muscular system
Topics	Muscular tissue • Muscle contraction • Muscles of the human body
Types of muscles	Cardiac muscle • Skeletal muscle • Smooth muscle

• • [ e] Histology: muscle tissue
skeletal muscle/general	epimysium, 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 muscle	myocardium, intercalated disc, nebulette
smooth muscle	calmodulin, vascular smooth muscle

American and British English spelling differences are one aspect of American and British English differences.

In the early 18th century, English spelling was not standardised. Different standards became noticeable after the publishing of influential dictionaries.
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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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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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1 centimetre =
SI units
010⁻³ m 0 mm
US customary / Imperial units
010⁻³ ft 0 in

A centimetre (American spelling: centimeter, symbol cm
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Biological tissue is a collection of interconnected cells that perform a similar function within an organism.

The study of tissue is known as histology, or, in connection with disease, histopathology.
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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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Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the
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'Cardiac muscle' is a type of involuntary striated muscle found within the heart. Its function is to "pump" blood through the circulatory system by contracting.
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Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the
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Embden-Meyerhof pathway, initially explained by Gustav Embden and Otto Meyerhof. The term can be taken to include alternative pathways, such as the Entner-Doudoroff Pathway. However, glycolysis will be used here as a synonym for the Embden-Meyerhof pathway.
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Myoglobin is a single-chain globular protein of 153 amino acids, containing a heme (iron-containing porphyrin) prosthetic group in the center around which the remaining apoprotein folds.
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Cellular respiration describes the metabolic reactions and processes that take place in a cell or across the cell membrane to obtain biochemical energy from fuel molecules and the release of the cells' waste products.
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Poultry is the category of domesticated birds kept for meat, eggs, and feathers. These most typically are members of the order Galliformes (which includes chickens and turkeys) and the family Anatidae (in order Anseriformes), commonly known as "waterfowl" (e.g.
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chicken (Gallus gallus) is a type of domesticated fowl, believed to be descended from the wild Indian and south-east Asian Red Junglefowl.

The chicken is one of the most common and wide-spread domestic animals.
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Goose (plural geese, male gander(s)) is the English name for a considerable number of birds, belonging to the family Anatidae. This family also includes swans, most of which are larger than geese, and ducks, which are smaller.
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Fermentation is a process of energy production in a cell under anaerobic conditions (with no oxygen required). In common usage fermentation is a type of anaerobic respiration, however a more strict definition exists which defines fermentation as respiration under anaerobic
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Sprints are short running races in athletics.
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Weightlifting is a sport in which competitors attempt to lift heavy weights mounted on steel bars called barbells, the execution of which is a combination of power, flexibility, concentration, skill, will power, disipline (very important) athleticness, fitness, technique, and
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Cortisone (ˈkÃ´rtəˌsōn or -zōn, IPA: ˈkɔrtɨˌsoʊn or -zoʊn)) (17-hydroxy-11-dehydrocorticosterone) is a steroid hormone.
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MeSH D009135 In medicine, a myopathy is a neuromuscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease (myo- Greek μυσ "muscle" + -pathy Greek "suffering").
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A myoblast is a type of stem cell that exists in muscles. Skeletal muscle cells are called muscle fibers and are made when myoblasts fuse together; muscle fibers therefore have multiple nuclei.

Myoblasts that do not form muscle fibers differentiate into satellite cells.
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Medical College of Georgia is the smallest of four research schools in the University System of Georgia (USG). MCG currently has 5 undergraduate and graduate schools on campus: The School of Medicine, School of Dentistry, School of Nursing, School of Allied Health, and Graduate
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Duke University is a private coeducational research university located in Durham, North Carolina, USA. Founded by Methodists and Quakers in the present-day town of Trinity in 1838, the school moved to Durham in 1892.^[9] In 1924, tobacco industrialist James B.
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The muscular system is the biological system of an organism that allows it to move. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous.
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