Fill in the blank:  A withdrawal reflex employs a total of _______________________ neurons.

Background:  A doctor conducted a patellar tendon (aka knee jerk - covered in lecture, assigned reading, and laboratory) reflex test on a patient. To do so, she tested the patient's knee-jerk reflex by hitting the patient's patellar tendon with a rubber hammer.For this patient, the doctor observed that hitting the tendon caused no knee jerk reflex at all, even after many attempts.Normally, a patient will kick her lower leg after the hammer hit on the tendon.However, the doctor could stimulate contraction of the quadriceps leg muscles using a stimulating electrode that applied a voltage across the muscle. The doctor, with further analysis, determined that the receptor membranes of the stretch receptors were operating correctly.To do this, she carefully inserted an electrode into a stretch receptor's membrane, near to the location on the membrane where receptor  proteins are located. She measured a change in voltage while hitting the tendon with the hammer. With further testing, the…

Testing the patellar reflex in a patient is a good indicator of overall brain function. True or false