Patellar reflex is the scientific name for the layman’s term called knee jerk. It is tested to check the reflexes of an individual to a sensation.
Whenever you might have gone to a doctor for a problem, which may have a connection with sensory faculties, the doctor must have tapped a bit under your knee with a tendon hammer. The sensation and the reflex, which comes from that, not realized by us, is analyzed by the doctor. Now, this is actually a type of deep tendon reflex and is a stretch reflex. The text to come will tell you more about patellar reflex.
This test is done with the help of a tendon hammer. The doctor while doing this test, strikes the patellar tendon hammer a bit below the knee cap (patella), which stretches the quadriceps muscles in the thighs. Basically, this is the test to see how is the sensory response to the tapping by the tendon hammer. The main aim of testing is to analyze if the nervous system is in good shape or not. Simply put, after the doctor taps the tendon, the leg is extended, and then it comes to rest.
If the reflex is not up to the mark or is not there at all, it is referred to as Westphal’s sign. On the contrary, if there is multiple oscillation in response to the tap, that could indicate a cerebellar disease. It all happens because of the reflex arc from stimulus to response. A reflex arc is a neural pathway which mediates a reflex action. In a patellar reflex, nerve root is the carrier of an impulse by the motor neuron along its axon.
Somatic or Autonomic
This reflex is a somatic reflex arc, which affects the muscles. It is a stretch reflex when a muscle or tendon is struck or hit. The jolt leads the muscle to contract, which in turn inhibits the muscle contraction as a result of being struck. They are fundamentally spinal reflexes, mediated by the spinal cord. The catch here is even the message reaches the spinal cord and the brain together, the response is reflexed by the trigger without waiting for the brain to analyze the situation.
It is a withdrawal reflex, also called flexor through the somatic nervous system. In this, the nerve root is the carrier of an impulse by the motor neuron along its axon. The impulse then travels through the spinal nerve to the quadriceps muscles. Finally, acetylcholine is released, which causes contraction of muscle.
Connection with Exercise
Apparently, mild exercise does have a slight impact on this tendon. The reflex time appears to be shorter after mild exercise. But no connection was established between the time for reflex and neuromuscular excitability. There is another dimension to this, the impact of your mental state on this reflex. There are few tests to check if the 2 are connected. It depends from person to person, but one thing is sure that the more the mental activity the more noticeable the response.
Patellar tendon reflex test and analysis in short is done when damage to motor nerve or spinal cord has to be confirmed or checked. So, even if the patient does not realize that his knee has given a jerk, the doctors get what they want out of the test. Consequently the patient is told whether there is any problem or not.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be used as a replacement for expert medical advice.