![]() The tendon organ is a stretch receptor that signals the force developed by the muscle. Mammalian tendon organ showing typical position in a muscle (left), neuronal connections in spinal cord (middle) and expanded schematic (right). Inside the capsule, the afferent fibers lose their medullary sheaths, branch, intertwine with the collagen fibers, and terminate as flattened leaf-like endings between the collagen strands (see figure). The capsule is connected in series (along a single path) with a group of muscle fibers ( 10-20 fibers ) at one end, and merge into the tendon proper at the other.Įach capsule is about 1 mm long, has a diameter of about 0.1 mm, and is perforated by one or more afferent type Ib sensory nerve fibers ( Aɑ fiber), which are large (12-20 μm) myelinated axons that can conduct nerve impulses very rapidly. ![]() The body of the Golgi tendon organ is made up of braided strands of collagen (intrafusal fasciculi) that are less compact than elsewhere in the tendon and are encapsulated. The Golgi tendon organ is one of several eponymous terms named after the Italian physician Camillo Golgi. It provides the sensory component of the Golgi tendon reflex. It lies at the interface between a muscle and its tendon known as the musculotendinous junction also known as the myotendinous junction. If you read the article on the muscle spindle, you’ll now be able to understand that these two proprioceptors are essential to how the musculoskeletal system reacts to internal and external changes.The Golgi tendon organ ( GTO) (also called Golgi organ, tendon organ, neurotendinous organ or neurotendinous spindle) is a proprioceptor – a type of sensory receptor that senses changes in muscle tension. The protective mechanism of the GTO is debatable because we have a conscious level of awareness of how much load our muscles are taking, and so we are able to voluntarily adjust ourselves to decrease that load. This brings to our attention the fact we are aware of muscle tension but not muscle length. There are other connections to the cerebrum as well, which is why we have conscious awareness of changes in muscle tension - for example, imagine holding a cup in mid-air without changing the position of your arm: we’re aware of the tension building in our muscles and are forced to bring the cup down when we cannot manage the load. Through spinocerebellar tracts they also inform cerebellum of changes in muscle tension. They ultimately synapse on anterior horn cells which are inhibitory neurons- hence the negative feedback as was mentioned before. The afferent nerve pathway is through fast Ib nerves, which connect with the dorsal horn of the spinal cord. When the load on the muscle increases beyond a certain point, it causes an instantaneous relaxation of the muscle which is known as “the lengthening reaction”. The summation of the above mentioned effects helps to spread the load on the muscle, to distribute it equally and prevent damage by excessive load. If the tension in the muscles increases, the GTO is stimulated and causes muscle relaxation.ĭecreased tension decreases the stimulation of the GTO, leading to reflex contraction.Īt different parts of the tendon there are some areas with increased tension and some with decreased tension (reflecting the tension in the muscle itself). This probably evolved as a protective mechanism to prevent damage from excessive load. The GTO is mainly an inhibitory organ i.e., it gives negative feedback to the muscles. It is the state of contraction of the muscle fibres that thus exert a force on an object. ![]() What do we mean by tension? It is a complex concept, but simply put, muscle tension is regarded as force exerted by muscle on an object. Essentially, the GTO reads tension in the muscle. Ten to fifteen muscle fibres are connected to one GTO.
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