Motor Unit

Information about Motor Unit

A motor unit is a single α-motor neuron and all of the corresponding muscle fibers it innervates. When a motor unit is activated, all of its fibers contract. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units that subserve a single muscle are considered a motor unit pool.

The number of muscle fibers within each unit can vary: thigh muscles can have a thousand fibers in each unit, eye muscles might have ten. In general, the number of muscle fibers innervated by a motor unit is a function of a muscle's need for refined motion. The smaller the motor unit, the more precise the action of the muscle. Muscles requiring more refined motion are innervated by motor units that synapse with fewer muscle fibers.

In medical electrodiagnostic testing for a patient with weakness, careful analysis of the "motor unit action potential" (MUAP) size, shape, and recruitment pattern can help in distinguishing a myopathy from a neuropathy.

• • [ 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

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.
..... Click the link for more information.

A nerve is an enclosed, cable-like bundle of axons (the long, slender projection of a neuron). Neurons are sometimes called nerve cells, though this term is technically imprecise since many neurons do not form nerves, and nerves also include the glial cells that
..... Click the link for more information.

MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
..... Click the link for more information.

In humans the thigh is the area between the pelvis and buttocks and the knee. Anatomically, it is part of the lower limb.

The single bone in the thigh is called the femur.
..... Click the link for more information.

Eyes are organs of vision that detect light. Different kinds of light-sensitive organs are found in a variety of organisms. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors.
..... Click the link for more information.

synapse. Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical impulses into chemical signals.]]

Chemical synapses
..... Click the link for more information.

Electromyography (EMG) is a technique for evaluating and recording physiologic properties of muscles at rest and while contracting. EMG is performed using an instrument called an electromyograph, to produce a record called an electromyogram.
..... Click the link for more information.

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").
..... Click the link for more information.

Neuropathy
Classification & external resources

ICD-10 G 56. - G 63. ,
G 90.0 , G 99.0
ICD-9 337.0 - 337.1 ,
356 - 357 , 377

eMedicine topic list Neuropathy is usually short for peripheral neuropathy
..... Click the link for more information.

Motor unit recruitment is the progressive activation of a muscle by successive recruitment of contractile units (motor units) to accomplish increasing gradations of contractile strength. A motor unit consists of one motor neuron and all of the muscle fibres it contracts.
..... Click the link for more information.

A tetanic contraction occurs when a motor unit has been maximally stimulated by its motor neuron. It often occurs during tetanic stimulation of the motor unit, usually muscle or nerve.
..... Click the link for more information.

Motor Unit Number Estimation (MUNE) is a technique that uses electromyography to estimate the number of motor units in a muscle.

Principles

A motor unit consists of one alpha motoneuron and all the muscle fibres it innervates.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

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
..... Click the link for more information.

Perimysium is a sheath of connective tissue which groups individual muscle fibers ( anywhere between 10 to 100 or more) into bundles or fascicles

External links

Histology at cytochemistry.

..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... Click the link for more information.

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.
..... 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.
..... 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.
..... Click the link for more information.

Nebulin is an actin-binding protein which is localized to the I-band the sarcomeres in skeletal muscle. It is a very large protein (600-900 kDa) and binds as many as 200 actin monomers.
..... Click the link for more information.

This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.

Herod_Archelaus

iPedia Free Information Center