Why is it that most spinal nerves carry fibers of all four functional modalities but the majority of cranial nerves carry only one, two, or three functional neuronal types?
Spinal nerves are distributed to regional segments of neck/trunk/limbs. These areas contain skeletal m.t.(SE), smooth m. in vessel walls and gl. epithelium in sweat glands (VE), all have cutaneous receptors and sensory neurons from bones, muscles and joints (SA) and all have sensory receptor in vessel walls (VA). Many cranial nerves are much more limited in the distribution