Tendons are the structures which connect our muscles to the bone and are made up flexible fibrous tissue band. Due to the presence of tendons you can walk, run, jump or lift and can be mobile in different ways. The contraction of muscles causes the movement and force that is transmitted for muscle contraction is induced by tendons. Golgi tendon organ is also known as the tendon organ.
Golgi tendon organ are placed where the muscles fibers of the skeletal muscles join the tendons. Golgi tendon organ is composed of nerve tissue and collagen strands. Also known as neurotendinous organ or neurotendious spindle, it is a type of proprioceptive sensory receptive organ. In the late 19th century and also at the start of 20th century, Camillo Golgi, a renowned Italian physician discovered this organ and hence is named after him. He also made various other discoveries related to the functioning of nervous system in human body.
The structure of golgi tendon organ is composed of collagen strands that are connected with muscle fibers at one end and blend with tendon proper at the other end. Each golgi tendon organ is innervated via sensory fiber of single afferent which branches further and end up as spiral endings surrounding the collagen strands. The afferent axon present in this tendon organ has huge diameter and is a type of myelinated axon. A fibrous capsule constituting several enlarged tendon fascicule (intrafusal fascicule) encloses the golgi tendon organ. The sides of the capsules are perforated by several nerve fibers that lose medullary sheaths. The axis cylinders present subdivide further and end up into tendon fibers forming irregular discs.
When the force is generated by the muscles, the sensory terminals are compressed. Due to this stretching, the afferent axon terminals are deformed. This process opens the stretch sensitive cation channels and depolarizes the axon firing nerve impulses that are propagated to spinal cord. This whole action potential frequency transmits the message of force that is being developed by the several motor units located inside the muscles. This entire process signifies the complete muscle force. Earlier it was believed that the golgi tendon organs had a very high sustenance and could only become active under very high stress of muscle forces. And this further led to the belief that the input of tendon organ resembled the weigh lifting failure by means of clasp-knife reflex. This action has been found to protect the tendons and also the muscles from excessive stress or force.
During the muscle building and stamina building sessions, the weight lifters are very keen to steadily enhance the measure of weight they can handle. This action is particularly associated with the golgi tendon organ and hence muscle builders are particularly interested in it. According to some trainers, making the muscles do additional repetitions by using highly heavy weights helps in stopping the muscles from failing in the next attempt. But physicists are of the opinion that golgi tendon organ always respond to muscle tension and immediately send this information to brain. So, the muscle stretching pulls on the tendons thereby stimulates the afferent of golgi tendon organ. Since the force causing the stretch is absorbed mostly by the muscle, muscle contraction acts as a stimulus for golgi tendon organ.