Inverse Stretch Reflex PDF

Inverse stretch reflex (Golgi tendon reflex) Whereas stretch reflex causes muscle contraction in response to increased muscle length (stretch), the disynaptic Golgi tendon reflexes produce exactly the opposite effect: muscle relaxation and lengthening in response to tension. Over stretch of the musc...

Inverse stretch reflex (Golgi tendon reflex) Whereas stretch reflex causes muscle contraction in response to increased muscle length (stretch), the disynaptic Golgi tendon reflexes produce exactly the opposite effect: muscle relaxation and lengthening in response to tension. Over stretch of the muscle with increase in muscle tension lead to excitation of the high threshold Golgi tendon organs (GTOs) in the tendon, which fire impulses along thick myelinated afferent Type 1b sensory neuron and stimulate inhibitory Effect of stimulation of the GTOs interneurons (Golgi bottle interneurons). With subsequent inhibition of the alpha motor neuron supplying the contracting muscle and activation of the antagonist muscles. As a result, the contracting muscle relaxes as its antagonist is activated. Golgi tendon reflex is a protective reflex help to avoid tearing of muscles and tendons subjected to possibly damaging stretching force. Golgi tendon organs also function at normal muscle tension. In the normal range, Golgi tendon organs help to ensure smooth onset and termination of muscle contraction. Therefore, muscle spindles are not the only source of proprioceptive inputs from the muscle, GTOs monitors muscle tension or the force of contraction. This reflex can be detected easily in cases of upper motor neuron lesion producing what's called. "Clasp knife spasticity". This means that in cases of upper motor neuron lesion e.g. passive flexion of elbow joint will show initial resistance, but with more flexion (overstretch of triceps muscle i.e. antagonist muscle). The triceps muscle will relax, and the initial resistance disappears. Clonus Figure: clasp knife reflex Rhythmic alternative muscle contraction and relaxation that develops in response to sudden maintained muscle stretch Mechanism of clonus Clonus is the result of a stretch reflex- inverse stretch reflex sequence. The initial sudden muscle stretch will stimulate discharge from intrafusal fibers (mainly nuclear bag) resulting in muscle contraction (stretch reflex). The tension developed in the muscle because of contraction is so high that the Golgi tendon organ becomes, excited initiating Figure: clonus inverse stretch reflex in the same muscle producing its relaxation, and as the stretch is maintained this process will be repeated rhythmically helped by the state of excessive supraspinal facilitation in case of upper motor neuron lesion.