Interrupted reflex arc

Introduction The structural basis of the reflex activity is called the reflex arc, including the receptor, the afferent nerve, the nerve center, the efferent nerve, and the effector. Simply put, the reflection process is carried out as follows: a certain stimulus is felt by a certain receptor, and the receptor is excited; the excitement is transmitted to the center through the afferent nerve in a nerve impulse; through the central analysis and comprehensive activities, the central generation Excitement; the excitement of the center reaches the effector through a certain efferent nerve, causing the effector to have corresponding activities. If the central nervous system is restrained, the original impulse of the central artery is weakened or stopped. Under experimental conditions, artificial telestimulation directly acts on the afferent nerve and can also cause reflex activity. However, under natural conditions, the reflex activity generally needs to be tested through a complete reflex arc. If any part of the reflex arc is interrupted, the reflection is Can't happen.

Cause

1. Decreased or disappeared indicates that the reflex arc is damaged or interrupted. It is also seen in neuromuscular joints or muscle diseases such as myasthenia gravis and periodic paralysis. Anesthesia, coma, deep sleep, spinal cord shock, increased intracranial pressure, especially posterior fossa tumors, deep reflexes also decreased or disappeared.

2, hyperthyroidism is more common in pyramidal tract lesions, coma or anesthesia can also occur early, caused by the suppression of spinal reflex arc, also seen in the excitability of muscles such as hand, foot and tetanus. Deep reflexes of rickets or other neurosis are also often hyperactive.

an examination

Related inspection

Electroencephalogram examination

The deep reflection of normal people can also be advanced, and the old Achilles tendon reflex can disappear, so the asymmetry of reflection is more meaningful than the enhancement or disappearance.

The reflex examination is more objective, but the patient still needs to cooperate, the limbs are relaxed, and the symmetry and proper position are maintained. Percussion hammer sniper force should be even and appropriate. During the examination, you can talk to the patient or squat the patient to read, cough or pull the two hands to pull the muscles to relax the spirit to facilitate the reflex.

Differential diagnosis

1. biceps tendon reflex (neck 5-6, musculocutaneous nerve): the forearm is semi-flexible, slamming the thumb placed on the biceps tendon, causing the forearm to flex, and at the same time feeling the contraction of the biceps tendon.

2. triceps tendon reflex (neck 6-7, phrenic nerve): the forearm is semi-flexed and pre-rotated, holding the elbow, slamming the triceps tendon above the eagle, causing the forearm to stretch.

3. Periosteal reflex (neck 5-8, phrenic nerve): Forearm semi-flexion, slamming the styloid process of the humerus, causing forearm flexion, pronation and finger flexion.

4. Knee reflex (waist 2-4, femoral nerve): sitting position, the two calves naturally hang or foot on the ground; or supine, knee slightly bent, with the hand to hold the nest, slamming the lower quadrant of the tibia tendon tendon, caused The calves are straight.

5. Achilles tendon reflex (1-2, phrenic nerve): supine, knee flexed, legs apart, with a light hand on the foot to make a slight dorsiflexion, slamming the Achilles tendon caused by the foot.

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