1. CRANIAL NERVES - LECTURE B
NBIO 401 – Friday, October 8, 2009

2. Abducens
nucleus
Abducens
nerve
This computer reconstruction shows the position and course of the abducens nucleus and nerve at the junction of the pons rostrally and the medulla caudally.

3. Genu of
the Facial
nerve
Abducens
nucleus
In this reconstruction we can see the facial nucleus and its axons. Note the course of the axons which leave the nucleus traveling dorsomedially, loop around the dorsomedial edge of the abducens nucleus and then course ventrolaterally to exit the ventrolateral side of the brainstem.
Facial
nucleus
Facial
nerve

4. Abducens Nucleus Facial nerve fibers Facial motor nucleus
(eye muscle motoneurons)
Facial nerve fibers
(looping around the abducens nucleus)
Facial motor nucleus
(muscles of
facial expression)
In this section, the same one presented previously, we can see the abducens and facial nuclei and the axons of the facial nucleus looping over the abducens nucleus.

5. Superior salivatory nucleus
Solitary nucleus
(outside)
Abducens
nucleus
Superior salivatory nucleus
Facial intermediate nerve
part of facial nerve carrying:
Motor
motor output from the
superior salivatory nucleus
to some salivary glands (GVE)
Sensory
1) taste information from
the anterior 2/3 of the tongue to
solitary nucleus via the solitary
tract (SVA)
2) touch information from a
small patch of skin on the ear and
behind the ear to spinal trigeminal
nucleus (GSA)
In addition to carrying motor commands to the muscle of facial expression the facial nerve carries three other types of signals. These signals are carried in a particular part of the facial nerve, the facial intermediate nerve, that does not have the same course inside the brain as the facial motor fibers. This diagram shows the course of the facial intermediate nerve, describes the 3 types of signals that it carries and shows the positions of the superior salivatory nucleus and solitary tract & nuclei.
Spinal trigeminal
nucleus
Facial
intermediate
nerve
Solitary tract
(inside)

6. Superior cerebellar peduncle
Spinocerebellar fibers
(on route to the cerebellum)
Inferior cerebellar peduncle
Middle cerebellar peduncle
Superior cochlear nucleus
Vestibulocochlear Nerve VIII
Cochlear component
(carries auditory signals from the
cochlea to the cochlear nucleus)
The VIIIth nerve contains two types of axons, those carrying auditory signals and those carrying vestibular signals (related to movement of the head in space). This diagram shows the VIIIth nerve entering the dorsolateral medulla and terminating in the superior cochlear nucleus above the inferior cerebellar peduncle.

7. Vestibulocochlear Nerve VIII
Inferior
vestibular
nucleus
Medial
vestibular
nucleus
Vestibulocochlear Nerve VIII
vestibular component
(carries vestibular signals from the
vestibular labyrinth to the vestibular nuclei)
Inferior
Cerebellar
peduncle
Here we see the other, vestibular, division of the VIIIth nerve terminating in the vestibular nuclei medial to the inferior cerebellar peduncle.

8. Superior Cochlear nucleus Vestibulocochlear Nerve VIII
This computer reconstruction shows the relative positions of the cochlear nucleus, the vestibular nuclei and the vestibulocochlear nerve coming into the dorsolateral part of the brainstem.
Vestibular nuclei

9. Spinal trigeminal
nucleus & tract
Inferior cerebellar
peduncle
(spinocerebellar
fibers to cerebellum)
Vestibular
nuclei
Hypoglossal
Nucleus
Solitary tract
& nucleus
MLF
Cochlear Nucleus
(auditory information)
Spinothalamic
Tract
Medial
lemniscus
Inferior
olive
nucleus
In this cross section of the rostral medulla we see, in the upper left, the position of the cochlear nucleus above the inferior cerebellar peduncle and the vestibular nuclei medial to the peduncle.
Pyramidal
Tract
Abducens
nerve
(to eye muscle)
Pontine
Gray matter
(relay signals to cerebellum)

10. Inferior salivatory nucleus
Solitary nucleus & tract
Spinal trigeminal Nucleus
Nucleus Ambiguus
(motoneurons for
larynx & pharynx
muscles)
Glossopharyngeal nerve IX
carries:
Motor
signals to the pharynx
from nucleus ambiguus
motor output from the inferior
salivatory nucleus to some salivary
glands
Sensory
1) taste information from posterior
1/3 of tongue to the solitary nucleus
via the solitary tract.
touch information from the posterior
1/3 of the tongue, pharynx, some skin
around the ear, internal surface of ear drum
to the spinal trigeminal tract
Pressure signals from the carotid
artery
The glossopharyngeal nerve IX is small but carries three types of signals. This diagram shows the course of the glossopharyngeal nerve, describes the 3 types of signals that it carries, and shows the positions of the inferior salivatory nucleus and solitary tract & nuclei.

11. Dorsal
motor nucleus
of the Vagus
Solitary
nucleus & tract
Nucleus
ambiguus
Spinal
trigeminal
nucleus
Roots of the vagus nerve X carries:
Motor
motor signals to larynx & pharynx muscles from motoneurons in nucleus ambiguus.
2) parasympathetic output to the larynx & pharynx & to organs of the chest & abdomen from the dorsal
motor nucleus of the vagus
Sensory
touch signals from pharynx, external ear canal, external side of the ear drum, & skin of the ear
to the spinal trigeminal nucleus.
2) taste information from the epiglottus to the solitary nucleus
3) sensory signals from the larynx, trachea, esophagus, chest & abdomen viscera, & pressure & chemoreceptors
in the aorta to the caudal part of the solitary nucleus.
The vagus nerve X, exits the lateral surface of the medulla as a line of small rootlets just caudal to where the glossopharyngeal rootlets exit the medulla. Like the facial and glossopharyngeal nerves the vagus nerve has several components. This diagram shows the course of the vagus fibers inside the medulla, describes the 4 types of signals that it carries, 2 motor and 3 sensory, and shows the positions of the inferior dorsal motor nucleus of the vagus, the solitary tract & nuclei, the nucleus ambiguus, and the spinal trigeminal nucleus. The dorsal nucleus of the vagus is a cell column dorsal and medial to the the solitary nucleus and tract and immediately lateral to the hypoglossal nucleus. Note that the solitary nuclei move medially and converge in the caudal medulla.

12. Inferior olive nucleus
Medial lemniscus
(touch information
from body)
Spinothalamic
Tract
Spinocerebellar
Pyramids
Spinal trigeminal
nucleus & tract
Hypoglossal
Nucleus
(tongue
motoneurons)
Lateral
cuneate
nucleus
Inferior olive nucleus
(big input to cerebellum)
Vestibular
nuclei
Hypoglossal nerve
(motor commands to tongue)
MLF
DMX
Nucleus Ambiguus
(motoneurons for larynx
& pharynx muscles)
Solitary tract
& nucleus
Vagus Nerve Rootlet
(motor commands
to viscera in body)
In the top part of this cross section through the rostral medulla we can see the position of the dorsal motor nucleus of the vagus, labeled DMX, dorsal and medial to the solitary tract and nucleus and immediately lateral to the hypoglossal nucleus. Note the vagus nerve rootlets visible exiting the lateral surface of the on both sides.

13. Spinal accessory nucleus
(motoneurons for
sternocleidomastoid
& trapezius muscles)
Spinal
accessory
nerve
Spinal
accessory
roots
This reconstruction shows the position of the accessory nucleus, roots, and nerve XI. The accessory nerve provides the motor innervation to the sternocleidomastoid and trapezius muscles. The motor nucleus is in the lateral part of the ventral horn of the upper five or six cervical segments of the spinal cord gray matter. The rootlets ascend through the foramen magnum, then loop back out of the skull via the jugular foramen.

14. Spinal Accessory Nucleus
Gracile fasciculus
Gracile Nucleus
Cuneate nucleus
Cuneate fasciculus
Spinal
trigeminal
nucleus & tract
Spinal Accessory
Nucleus
In this section through the most caudal part of the medulla we see the rostral end of the spinal accessory nucleus ventral in the gray matter and medial to the spinal trigeminal trigeminal nucleus and tract.
MLF
Pyramidal Decussation
Spinothalamic
Tract
Pyramidal tract

15. Solitary
nucleus
& tract
Vestibular
nuclei
Dorsal motor nuclei
of the vagus
External cuneate
nucleus
Spinal trigeminal
nucleus & tract
Nucleus
ambiguus
Hypoglossal nuclei
(motoneuron for
tongue muscles)
Inferior olive
This computer reconstruction shows the position of the hypoglossal nucleus XII near the midline and on the dorsal surface of the medulla, and the course of the axons leaving the nucleus to exit the ventrolateral surface of the medulla between the pyramidal tract and the inferior olive.
Hypoglossal
nerve
Pyramidal
tract

16. Spinal trigeminal
nucleus & tract
Vestibular
nuclei
Hypoglossal
Nucleus
Solitary tract
& nucleus
Lateral cuneate
nucleus
DMX
IVth
ventricle
Inferior olive
In this section we can see see the position of the hypoglossal nucleus dorsal and medial in the medulla. White arrows point to hypoglossal axons as they course ventral and lateral along the lateral edge of the medial lemniscus and then turn laterally between the inferior olive and pyramidal tract where they exit.
Pyramidal tract
Medial lemniscus

17. Somatic Motor Nuclei Oculomotor nucleus Hypoglossal nucleus Oculomotor
nerve
Trochlear
nerve
Hypoglossal
nerve
This computer reconstruction summarizes the somatic motor cranial nerve nuclei.
Trochlear
nucleus
Abducens
nerve
Abducens
nucleus

18. Special visceral (Branchial) Motor Nuclei
Trigeminal
motor nucleus
Trigeminal
nerve
Facial
motor nerve
Facial
motor nucleus
This diagram summarizes the special visceral (branchial) efferent cranial nerve nuclei.
Nucleus ambiguus
axons bound for
glossopharyngeal
& vagus nerves
Nucleus
ambiguus

19. General Visceral Motor Nuclei
Dorsal motor nucleus of the vagus
Axons from the dorsal motor nucleus
of the vagus bound for the vagus nerve
Inferior salivatory nucleus
Superior salivatory nucleus
Axons from the
superior salivatory nucleus
bound for the facial nerve
Axons from the inferior
salivatory nucleus bound
for the glossopharyngeal nerve
This diagram summarizes the general visceral efferent cranial nerve nuclei. Note in this image that the brainstem is rotated so that caudal is upper left and rostral is lower right. This reconstruction highlights the nuclei that provide the preganglionic innervation to parasympathetic ganglia in the head and in the thorax and abdomen.
Edinger-Westphal
nucleus
Edinger-Westphal
fibers bound for
the oculomotor nerve

20. Somatic Sensory Nuclei
Spinal
trigeminal
nerve
nucleus
Mesencephalic
trigeminal nucleus
Main sensory
trigeminal tract
Trigeminal nerve
(touch, conscious& unconscious
proprioception, pain & temperature
from the head to main sensory
trigeminal nucleus, mesencephalic
trigeminal nucleus & spinal
trigeminal nucleus)
Vagus nerve
(touch from ear
& pharynx to
spinal trigeminal)
Glossopharyngeal
Nerve
(touch from ear & pharynx
to spinal trigeminal)
Facial intermediate nerve
(touch from ear to spinal
Somatic Sensory Nuclei
This diagram summarizes the somatic cranial nerve nuclei and the tract that bring signals to them.

21. Visceral Sensory Nuclei Glossopharyngeal nerve
Facial intermediate
Nerve (taste from anterior
2/3 of tongue to solitary
nucleus)
Glossopharyngeal nerve
(taste from posterior 1/3
of tongue to solitary nucleus)
Here we see a summary of visceral sensory cranial nerve nuclei and the nerves that bring signals to them.
Vagus nerve
(taste from epiglottus to rostral solitary nucleus,
signals from the trachea, esophagus,
chest, abdomen & aorta to
caudal part of solitary nucleus)