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Structure of a skeletal muscle. A key component in lateral force transmission in skeletal muscle is the extracellular matrix (ECM). Skeletal muscle is a complex biological material that is composed of muscle fibers and an ECM consisting of the epimysium, perimysium, and endomysium. It can be described as a collagen fiber-reinforced composite.
The number of muscle fibers within each unit can vary within a particular muscle and even more from muscle to muscle: the muscles that act on the largest body masses have motor units that contain more muscle fibers, whereas smaller muscles contain fewer muscle fibers in each motor unit. [1]
Broadly there are two types of muscle fiber performing in muscle contraction, either as slow twitch or fast twitch . A single muscle such as the biceps brachii in a young adult human male contains around 253,000 muscle fibers. [11] Skeletal muscle fibers are the only muscle cells that are multinucleated with the nuclei usually referred to as ...
A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
Single fiber electromyography assesses the delay between the contractions of individual muscle fibers within a motor unit and is a sensitive test for dysfunction of the neuromuscular junction caused by drugs, poisons, or diseases such as myasthenia gravis.
Each individual muscle fiber is innervated by only one motor neuron, but one motor neuron may innervate several muscle fibers. This distinction is physiologically significant because the size of a given motor pool determines the activity of the muscle it innervates: for example, muscles responsible for finer movements are innervated by motor ...
Type Aα fibers include the type Ia and type Ib sensory fibers of the alternative classification system, and are the fibers from muscle spindle endings and the Golgi tendon, respectively. [1] Type Aβ fibres, and type Aγ, are the type II afferent fibers from stretch receptors. [1] Type Aβ fibres from the skin are mostly dedicated to touch.
A myofibril (also known as a muscle fibril or sarcostyle) [1] is a basic rod-like organelle of a muscle cell. [2] Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. [3] Each myofibril has a diameter of 1–2 micrometres. [3]