Final answer:
A normal response to the brachioradialis reflex test is flexion and supination of the forearm, facilitated by the brachioradialis muscle upon stimulation, different from the triceps brachii which extends the forearm.
Step-by-step explanation:
The brachioradialis reflex test is a common neurological examination to test the proper function of the radial nerve which primarily innervates the brachioradialis muscle. A normal response to the brachioradialis reflex test is flexion and supination of the forearm. When this reflex is initiated, the forearm should bend at the elbow, and the palm should turn upwards slightly. This occurs due to the quick stretch reflex of the brachioradialis muscle when it is struck, which mainly involves forearm flexion. The muscles that contribute to this reflex and the movements of flexion and supination are particularly important in performing many daily activities.
Contrastingly, the muscle that extends the forearm is the triceps brachii. The origin of the wrist flexors is the medial epicondyle of the humerus, not the deltoid tuberosity or the carpal bones of the wrist. Understanding these muscle actions and origins can be helpful when assessing muscle function during a physical examination.