Jackknife phenomenon

Introduction The receptor (the sputum in the tendon) - the afferent nerve - the central (spinal cord) - the efferent nerve - the effector (muscle). When the tension of the stretched muscle is too large and exceeds a certain limit, it will cause the opposite reaction. It is not that the muscle tension is further strengthened but the whole muscle suddenly relaxes. This is called the elongation reaction. The process of this reaction is similar to the resistance of a folding knife with a spring to the folding knife, so it is also called a folding knife reaction. Myotonia is the result of enhanced stretch reflexes, and the stretch reflex threshold is reduced, resulting in increased resistance to passive motion. But when the muscles are stretched to the maximum extent, the resistance will suddenly disappear, which is the so-called "folding knife phenomenon."

Cause

When the muscle is stretched, the motor neurons that innervate the stretched muscle are affected by two antagonistic afferent impulses. One is excitatory, the other is inhibitory, and the output of motor neurons is determined by these two. The balance of a pair of antagonistic inputs. When excessively stretched, the inhibitory input becomes a decisive factor, producing a folding knife reflection.

an examination

Related inspection

Electromyography CT examination

Folding knife reflexes may be a protective mechanism to avoid excessive distraction and muscle breakage. It is now known that this reflex sensor is the scorpion (Golgi's sputum organ) in the tendon. It has a "tandem" relationship with muscle formation. Whether the muscle is stretched or the muscle itself shrinks, it can stimulate the afferent impulse to send into the spinal cord. It may be an excitatory inhibitory interneuron, and then inhibit the dominance. Muscle anterior horn motor neurons.

Differential diagnosis

Muscle strain: It is the damage caused by the muscle contracting or over-drawing during exercise.

Muscle strain: It is a chronic, repeated accumulation of microscopic damage. It often occurs in areas with excessive muscle activity or persistent muscle tension in static posture. Can be divided into two categories of acute and chronic. Common parts are the muscles of the waist, neck and legs.

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