Golgi tendon apparatus conveys message to CNS, depending upon –
Correct Answer: Tension in muscle
Description: Ans. A. Tension in muscleInverse stretch reflex-a. Up to a point, the harder a muscle is stretched, the stronger is the reflex contraction. However, when the tension becomes great enough, contraction suddenly ceases and the muscle relaxes. This relaxation in response to strong stretch is called the inverse stretch reflex.b. The receptor for the inverse stretch reflex is in the Golgi tendon organ. This organ consists of a netlike collection of knobby nerve endings among the fascicles of a tendon. There are 3-25 muscle fibers per tendon organ.c. The fibers from the Golgi tendon organs make up the Ib group of myelinated, rapidly conducting sensory nerve fibers. Stimulation of these Ib fibers leads to the production of IPSPs on the motor neurons that supply the muscle from which the fibers arise.d. The Ib fibers end in the spinal cord on inhibitory interneurons that in turn terminate directly on the motor neurons. They also make excitatory connections with motor neurons supplying antagonists to the muscle.e. Because the Golgi tendon organs, unlike the spindles, are in series with the muscle fibers, they are stimulated by both passive stretch and active contraction of the muscle. The threshold of the Golgi tendon organs is low.f. The degree of stimulation by passive stretch is not great because the more elastic muscle fibers take up much of the stretch, and this is why it takes a strong stretch to produce relaxation.g. However, discharge is regularly produced by contraction of the muscle, and the Golgi tendon organ thus functions as a transducer in a feedback circuit that regulates muscle force in a manner analogous to the spindle feedback circuit that regulates muscle length.h. The importance of the primary endings in the spindles and the Golgi tendon organs in regulating the velocity of the muscle contraction, muscle length, and muscle force is illustrated by the fact that section of the afferent nerves to an arm causes the limb to hang loosely in a semi paralyzed state. The interaction of spindle discharge, tendon organ discharge, and reciprocal innervation determines the rate of discharge of a-motor neurons
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Physiology
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