CBNS 116 Lecture 9 - Brainstem III: Cranial nerves III - XII and their nuclei
Lecture notes by Todd Fiacco
In Nolte read Chapter 12: “Cranial nerves and their nuclei”.
FOR NEXT LECTURE: No new assignment. The next reading assignment (for 5/6) will be
“hypothalamus and pituitary”, Nolte Ch. 23 pp. 580-591.
The big picture:
The cranial nerves are the somatosensory and motor nerves for the head.
Thus, they are the head’s equivalent of the spinal nerves of the spinal cord. Remember that in
addition to these basic sensory and motor functions, much of the parasympathetic innervation
of the head and viscera emerges from the brainstem (the
of craniosacral outflow; CNs
III, VII, IX, X). Furthermore, some cranial nerves carry additional, special modalities of
information. During development, much of the musculature of the head is derived from the
, the primordial gill arches (that develop into gills in fish). Thus several cranial
nerves (V, VII, IX, X, XI) carry branchial motor
, or special motor
, innervation to these
structures. In addition, the head contains specialized sensory structures (for vision, auditory,
balance, olfaction, and taste), and information reaches the CNS from these structures in
specific cranial nerves carrying special sensory
information (I, II, VII, VIII, IX, X). Thus the
cranial nerves together carry a total of 6 different modalities: 1) general somatosensory, 2)
general motor, 3) autonomic (visceral) sensory, 4) autonomic (visceral) motor, 5) special
(branchial) motor, and 6) special sensory information. All of the cranial nerves except I & II
carry their information to, or send their information from, the brainstem. The best way to learn
the cranial nerves is to organize them by modality
, as Nolte tries to do in Chapter 12.
I. Generally speaking, sensory cranial nerve nuclei are located laterally in the brainstem, while
motor nuclei lie medially
[slide 44]. We will look at cranial nerve function by modality, moving
from medial to lateral.
II. Cranial nerves III*, IV, VI, and XII are
somatic motor nerves
, and their nuclei lie along the
midline of the brainstem. (*CN III also contains a small amount of preganglionic
parasympathetic fibers to the pupillary sphincter muscle to constrict the pupil and to the