Final answer:
Deep tendon reflexes are tested by applying a strong tap to a tendon, which activates the muscle spindle and causes muscle contraction. This reflex helps maintain stability and indicates proper function of the lower motor neuron.
Step-by-step explanation:
To test deep tendon reflexes, a strong tap is applied to a tendon at its insertion point. Common reflexes tested are the biceps, brachioradialis, triceps, and flexors for the arm, and the reflex of the quadriceps and ankle reflex for the leg. When the tendon is struck, the muscle spindle is activated and sends a signal to the spinal cord, which then activates the motor neuron and causes muscle contraction. These reflexes are important for stability and indicate that the lower motor neuron is functioning properly.