![muscle spindle muscle spindle](http://educ.jmu.edu/~strength/KIN_425/Muscle_Spindles.jpg)
![muscle spindle muscle spindle](http://cf.ppt-online.org/files/slide/i/IozOADEFse3pSBl5V2Q9kNJWTHf1KmnqijuXyx/slide-12.jpg)
In contrast, GTO senses excessive tension of the muscle and inhibits muscle activation in order to decreases the tension of muscle and tendons. Muscle spindle senses the change in the length of the muscle as well as the speed of lengthening of the muscle. Muscle spindle and Golgi tendon organ (GTO) are two types of sensory organs present in the muscle– tendon unit. Thus, the muscle spindles and the Golgi tendon organs work in concert with each other to ensure that a particular muscle is held at the appropriate length and tension for a specific task.The key difference between muscle spindle and Golgi tendon organ is that muscle spindle is a sensory organ that senses the changes in muscle length and the rate of lengthening, while Golgi tendon organ is a sensory organ that senses the changes in muscle tension.
Muscle spindle series#
However, if the muscle tension increases excessively, the Golgi tendon organs, which are attached in series with the muscle, inhibit the activity of the amotor neurone, providing an inhibitory feedback mechanism to prevent muscle damage.
![muscle spindle muscle spindle](https://c8.alamy.com/comp/CT3YJ3/muscle-spindle-CT3YJ3.jpg)
This will stimulate the a motor neurone and thereby increase contraction of the motor unit. If, however, the limb meets with resistance, the intrafusal muscle fibres will shorten more than the extrafusal muscle fibres, the centre of the muscle spindle becomes stretched and the rate of firing in the afferent axons increases. If little resistance is encountered, both the extrafusal and intrafusal muscle fibres will contract at approximately the same rate, and as a result the central portion of the muscle spindle retains its original length before the contraction and little change in activity will be detected in the afferent axons of the spindle. Therefore by establishing a rate of firing in the y motor system, the higher centres control the length of the muscle spindles and indirectly the length of the entire muscle.ĭetails of nerve connections to the nuclear bag and nuclear chain muscle spindle fibresĭuring normal movements, both the a and y motor neurones are activated at the same time. However, when the y motor neurones are active, they become shorter and become much more sensitive to changes in muscle length. When the muscle spindles are relaxed, they are relatively insensitive to stretch. Furthermore, the sensitivity of the muscle spindle is adjustable. One of the most basic functions of the muscle spindle, therefore, is to maintain muscle length (see stretch reflex below). This should not to be confused with the Golgi tendon apparatus, which are stretch receptors within tendons and respond to the tension, not length, within the muscle. In other words, the muscle spindle acts as muscle length detector. However, the opposite occurs when the muscle relaxes or is stretched passively. When the muscle as a whole contracts, the muscle spindle relaxes and firing in its afferent axon stops. The central portion of the muscle spindle detects the change in length of the muscle.