A sensory organ in the muscle that relays information about length and speed of stretch to the central nervous system.
A type of receptor, located among the fibers of a skeletal muscle that responds to muscle contraction (stretch).
One of the sensory receptors which lie along striated muscle fibres.
A specialized receptor, sensitive to stretch, that is embedded between and parallel to the fibers of striated muscles. These receptors are important for coordinated muscular movement.
A specialized sensory fiber within a muscle that is sensitive to tension and changes in length of the muscle. The central region consists of a nuclear bag with primary or annulospiral receptor endings and several nuclear chains with primary endings and secondary, or flower spray, endings. Each end consists of intrafusal muscle fibers innervated by gamma motor nerves. When these fibers contract, tension on the central bag and chains results in feedback to the muscle fibers outside the muscle spindle, causing them to contract.