Muscle spindle

A type of mechanoreceptor found in the skeletal muscles of vertebrates. It is a spindle-shaped proprioceptor, also known as the muscle spindle. It is made up of several special muscle fibers (intraglued fibers) that are parallel to the striated muscle fibers and have sensory nerve endings attached to them, and sends afferent impulses to the central nervous system in response to muscle stretching. Near both ends of the intrafusal fibers are the endings of motor fibers (γ (gamma) efferent fibers), which regulate the length of the intrafusal fibers. Muscle spindles play an important role in controlling posture and regulating movement via the spinal reflex.

[Akira Murakami]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

脊椎(せきつい)動物の骨格筋中にある機械受容器の一種。紡錘形をした自己受容器で、筋紡錘体ともいう。横紋筋繊維と並列になった数本の特殊な筋繊維（錘内繊維）に感覚神経末端がついたもので、筋肉の伸張に応じて求心性インパルスを中枢に送る。錘内繊維の両端近くには運動繊維（γ(ガンマ)遠心性繊維）の終末があり、錘内繊維の長さを調節する。筋紡錘は脊髄(せきずい)反射を介して姿勢の制御や運動の調節に重要な働きをする。

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