Muscle Spindles

Muscle spindles are nerve cells which wrap around specialized muscle cells (so-called intrafusal fibres), which are stretched in coordination with the stretching of the muscle fibres. The firing rate of the muscle spindle neurons increases when the muscle fibres are stretched. This neural activity is involved in a feedback process (called the stretch reflex or myotatic reflex) in which muscle fibres are contracted as a result of the stretching of muscle fibres. Signals from muscle spindles are also involved in proprioception (the conscious perception of limb position).