Final answer:
The radial nerve controls movement of a muscle in the arm, particularly facilitating the extension of the forearm by innervating the triceps brachii muscle. It is also associated with the movement of the wrist and hand. correct answer is option D.
Step-by-step explanation:
The Radial Nerve's Function in the Arm
The radial nerve is crucial for controlling movement of a muscle in the arm. It innervates the posterior portion of the upper limb, facilitating movement and sensation in parts of the arm, forearm, and hand. Specifically, the radial nerve enables extension of the forearm through its innervation of the triceps brachii muscle, among other muscles that allow for movements of the wrist and hand. It is this nerve, not the trigeminal or facial nerves—which are involved in the gag reflex and facial expressions, respectively—that governs motor control of certain arm muscles.
Sympathetically, the radial nerve is influenced by neurons such as the sympathetic postsynaptic neuron, which releases norepinephrine to stimulate muscle contraction. It is distinct from cranial nerves like the trochlear or vagus nerves, which serve other functions including eye movement and autonomic control of organs respectively. The gag reflex, for instance, is controlled by cranial nerves IX and X—the glossopharyngeal and vagus nerves.