Intrafusal muscle fibers
Intrafusal Muscle Fibers
Intrafusal muscle fibers (pronounced: in-truh-FYOO-zuhl MUH-suhl FY-burz) are specialized muscle fibers with sensory functions. They are the main components of muscle spindles, which are sensory organs located within muscles.
Etymology
The term "intrafusal" is derived from the Latin words "intra", meaning "within", and "fusus", meaning "spindle". This refers to the location of these fibers within the muscle spindle.
Function
Intrafusal muscle fibers are responsible for detecting changes in muscle length and the rate of change in muscle length. They play a crucial role in the proprioceptive sensory system, which provides the brain with information about body position and movement.
Types
There are two main types of intrafusal muscle fibers: nuclear bag fibers and nuclear chain fibers. Both types are named for the arrangement of their nuclei.
Nuclear Bag Fibers
Nuclear bag fibers are so named because their nuclei are clustered in a central region, giving the fiber a "bag-like" appearance. They are sensitive to both the length and rate of change of muscle length.
Nuclear Chain Fibers
Nuclear chain fibers have nuclei arranged in a chain-like manner. They are primarily sensitive to the length of the muscle.
Related Terms
- Extrafusal muscle fibers: These are the standard skeletal muscle fibers that are responsible for muscle contraction.
- Gamma motor neurons: These neurons innervate intrafusal muscle fibers, adjusting the sensitivity of the muscle spindle.
- Proprioception: This is the sense of the relative position of one's own parts of the body and strength of effort being employed in movement.
External links
- Medical encyclopedia article on Intrafusal muscle fibers
- Wikipedia's article - Intrafusal muscle fibers
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