ABSTRACT
Muscle proprioceptors Two distinct kinds of proprioceptors are found in voluntary muscles, specialized for providing information about two quite different things: muscle spindles that respond to muscle length and rate of change of length, and Golgi tendon organs that signal muscle tension or force. Both are essentially stretch receptors: their difference in function comes about because of their different situation in the muscle as a whole. Whereas the spindles are in parallel with the main contractile elements in the muscle, so that their stretching is simply a measure of the degree of stretch x of the muscle itself, the tendon organs are situated in the muscle tendons, in series with the contractile elements and the load, so that their stretch is proportional to the tension T exerted by the muscle.
