How to Test Reflexes VIDEO Reflexes tested include the following: Biceps (innervated by C5 and C6) Radial brachialis (by C6) Triceps (by C7) Distal finger flexors (by C8) Quadriceps knee jerk (by L4) Ankle jerk (by S1) Jaw jerk (by the 5th cranial nerve) Any asymmetric increase or depression is noted.