Final answer:
The internal branch of the SLN is purely sensory.
Step-by-step explanation:
The internal branch of the Superior Laryngeal Nerve (SLN) is purely sensory.
According to the information provided, the SLN is a cranial nerve that participates only in sensory functions. Cranial nerves can be mixed nerves with both sensory and motor functions or purely sensory or motor. In the case of the internal branch of the SLN, it is strictly sensory, carrying sensory information into the brain.
It is important to note that the information provided specifically mentions the sensory function of the internal branch of the SLN.