Ten nerves relate to the brain stem as follow 4-4-2

1.the olfactory (I) and the optic nerves (II) are not true nerves but fiber tracts of the brain

2.the spinal accessory nerves (XI) is derived from the upper cervical cord segments.

1st 2 are purely sensory

last 2 are purely motor

3→motor (III,IV,VI)

3→mixed (motor and sensory) → (VII,IX,X)

4→ carry parasympathetiv fibers (III +mixed nerves)

5. 1and ½ → Cossing (part of III and IV)