<unk> s are stretch receptors within the body of a skeletal<unk>  that primarily detect changes in the length of the<unk> . They convey length information to the central nervous system via afferent nerve fibers. This information can be processed by the brain as proprioception. The responses of<unk> s to changes in length also play an important role in regulating the contraction of<unk> s, for example, by activating motor neurons via the stretch reflex to resist<unk>  stretch. The<unk>  has both sensory and motor components. * Sensory information conveyed by primary type Ia sensory fibers which spiral around<unk>  fibres within the<unk> , and secondary type II sensory fibers * Activation of<unk>  fibres within the<unk>  by up to a dozen gamma motor neurons and to a lesser extent by one or two beta motor neurons
Muscle spindle
Efferent nerve fiber
Postganglionic nerve fibers
Nerve plexus
Nerve fascicle
Muscle tissue
Cerebrospinal fibers
Sensory nerve