Final answer:
GVA fibers in the facial nerve are responsible for initiating salivation, playing a crucial role in the parasympathetic nervous system for digestion and oral health.
Step-by-step explanation:
The function of the GVA fibers within the facial nerve is to initiate salivation. These fibers are part of the parasympathetic nervous system and stimulate the salivary glands to produce saliva. This autonomic function is essential for beginning the digestive process and maintaining oral health.