Final answer:
The olfactory (CNI) and optic (CNII) nerves are the two cranial nerves considered extensions of the brain, responsible for smell and vision, respectively.
Step-by-step explanation:
The two cranial nerves that are considered direct extensions of the brain are the olfactory (CNI) and optic (CNII) nerves. The olfactory nerve is responsible for the sense of smell, and it transmits sensory information from the nose to the brainstem. The optic nerve is responsible for vision and transmits visual information from the eye to the brain. Unlike most other cranial nerves, these two do not emerge from the brainstem but instead directly from the cerebrum and diencephalon, respectively.