Neuroanatomy lecture by dr. Mohammed Mahmoud Mosaed Northern borderd faculty of medicine Al-azhar faculty of medicine

1. CRANIAL NERVE
NUCLEI
Dr. Mohammed Mahmoud
Mosaed

2. Neural tube
• The wall of a recently closed neural
tube consists of
neuroepithelial cells, they divide
rapidly, producing more and more
neuroepithelial cells which constitute
the neuroepithelial layer.
• Once the neural tube closes,
neuroepithelial cells begin to give
rise to another cell type, the primitive
nerve cells or neuroblasts which
form the mantle layer.
• The outermost layer of the neural
tube is the Marginal layer which
contains nerve fibers emerging from
neuroblasts in the mantle layer

3. Basal, Alar, Roof, and Floor Plates
As a result of continuous addition of neuroblasts to the mantle layer,
each side of the neural tube shows a ventral and a dorsal thickening.
The ventral thickenings, The Basal plates, which form the motor areas
in the neural tube;
The dorsal thickenings, The Alar plates, form the sensory areas.
The dorsal and ventral midline portions of the neural tube, known as the
roof and floor plates, respectively, do not contain neuroblasts

5. Cranial nerve nuclei in the brain stem
The basal plate contains motor nuclei which divided into 3 groups:
(a) General Somatic Efferent group (medial in position)
(b) Special Visceral Efferent group (intermediate)
(c) General Visceral Efferent group (lateral in position)
The alar plate contains 4 groups of sensory relay nuclei
(a) Special Somatic Afferent group (lateral in position), receives
impulses from the ear by way of the vestibulocochlear nerve.
(b) General Somatic Afferent receives impulses from the head and
face
(c) Special Visceral Afferent group receives impulses from taste buds
of the tongue and from the palate, oropharynx, and epiglottis.
(d) General Visceral Afferent, group (medial in position) receives
interoceptive information from the gastrointestinal tract and
heart

6. • Somatic refers to head, body wall, and extremities;
• Visceral refers to viscera;
• Afferent refers to sensory (input);
• Efferent refers to motor (output);
• General refers to wide areas of the head and body;
• Special refers to the specialized functions of olfaction (smell),
gustation (taste), vision, audition, equilibrium (vestibular system), and
branchiomeric muscles.
•All cranial nerve nuclei present in the brain stem except The
olfactory nerve (SVA) and the optic nerve (SSA) are telencephalic
derivatives, not brainstem cranial nerves Sensory nuclei where
afferent fibers terminate (called terminal nuclei)
•The nuclei of origin of motor fibers of the cranial nerves are
organized in discontinuous nuclear “columns” within the brainstem.

7. Cranial nerves
• The 12 Cranial Nerves
• There are 12 pairs of cranial nerves, which leave the brain
and pass through foramina and fissures in the skull. All the
nerves are distributed in the head and neck, except cranial
nerve X, which also supplies structures in the thorax and
abdomen. The cranial nerves are named as follows:
• 1. Olfactory 2. Optic
• 3. Oculomotor 4. Trochlear
• 5. Trigeminal 6. Abducent
• 7. Facial 8. Vestibulocochlear
• 9. Glossopharyngeal 10. Vagus
• 11. Accessory 12. Hypoglossal

9. MOTOR NUCLEI

10. The General Somatic Efferent Column
• It includes
• Nucleus of the oculomotor nerve (midbrain),
• Nucleus of trochlear nerve (lower midbrain),
• Nucleus of abducent nerve (lower pons)
• Nucleus of hypoglossal nerve (medulla).
• These nuclei are composed of lower motor
neurons innervating the voluntary muscles of the
eye and tongue.

11. The Special Visceral (Branchial)
Efferent Column
• It includes
• Motor nucleus (masticator nucleus) of the
trigeminal nerve (midpons),
• Motor nucleus of the facial nerve (the facial
nucleus) (lower pons),
• Nucleus ambiguus (medulla) of
glossopharyngeal, vagus and accessory
nerves

12. The General Visceral Efferent
Column (parasympathetic nuclei)
It includes:
The nucleus of Edinger–Westphal (midbrain).
The superior salivatory nucleus (posterior tegmentum of
lower pons).
The inferior salivatory nucleus (posterior tegmentum of
upper medulla).
The dorsal motor nucleus of the vagus nerve (posterior
tegmentum of medulla).
These nuclei are composed of cell bodies of preganglionic
parasympathetic neurons of the autonomic nervous
system.

14. SENSORY NUCLEI

15. The Special Somatic Afferent Column
It includes:
• The vestibular and cochlear nuclei of
the vestibulocochlear nerve, which
are located in the posterolateral
tegmentum of the upper medulla and
lower pons.
• Optic nerve which is a telencephalic
derivatievs

16. The General Somatic Afferent Column
It includes:
• The mesencephalic nucleus of trigeminal nerve
(proprioception), lies in the posteromedial midbrain
tegmentum,
• The main sensory nucleus of trigeminal nerve (crude
touch), located in the lateral midpontine tegmentum.
• The nucleus of spinal tract of trigeminal nerve (pain
and temperature), located in the lateral tegmentum of the
lower pons, medulla, and the upper two cervical spinal
cord segments (fibers from nerves V, VII, IX, and X
terminate in these nuclei).

17. The Visceral Afferent column
It consists of:
Special Visceral Afferent (smell and taste): The
nucleus solitarius located in the mid posterior
tegmentum of the medulla;
General Visceral Afferent: The nucleus solitarius
• The nucleus solitarius components include taste
(SVA) and other sensations from the viscera (GVA)
that enter the brainstem via facial, glossopharyngeal
and vagus nerves.

18. CRANIAL NERVES

19. Olfactory Nerve (n. I)
• The olfactory nerve
(SVA) is composed
of unmyelinated
axons that extend
from the nasal
mucosa to the
olfactory bulb.

20. Optic Nerve
Optic nerve (SSA)
• The optic nerve is
actually a tract of the
brain composed of
axons of retinal
ganglion cells,

21. Oculomotor, Trochlear and Abducent Nerves
• These cranial nerves have
lower motor neurons (GSE)
that innervate the extraocular
voluntary muscles and the
levator palpebrae muscle
(eyelid).
• The integrated actions of
these nerves are responsible
for conjugate movements of
the eye (called gaze;
simultaneous movement of
the two eyes in the same
direction).

22. Oculomotor nerve (III(
• 1. GSE
• Oculomotor nerve has motor fibers
(GSE) that innervate the extraocular
muscles (superior rectus, inferior
rectus, medial rectus, and inferior
oblique muscles) and the levator
palpebrae muscle (eyelid)
• 2. GVE
• From the nucleus of Edinger–
Westphal that innervates the
constrictor pupillae muscle and
ciliaris muscle

23. • Trochlear nerve (n. IV)
• The trochlear nerve has motor
fibers (GSE) innervates the
superior oblique muscle
• Abducent nerve (n.VI)
• Abducent nerve has motor fibers
(GSE) innervates the lateral
rectus muscle

24. Trigeminal Nerve
Nuclei of trigeminal nerve
1. Mesencephalic nucleus (proprioception)
2. Main sensory nucleus (touch)
3. Nucleus of the spinal tract of the
trigeminal nerve (pain and temperature)
4. Motor nucleus of trigeminal nerve

25. Type of fibers in trigeminal nerve
1. General Somatic Afferent (GSA)
The innervated region comprises the
face, orbit, mucous membranes of the
nasal cavity, nasal sinuses and oral
cavities, teeth, and most of the dura
mater. The fibers terminate in the main
sensory nucleus and the spinal nucleus
of trigeminal nerve. The
mesencephalic nucleus receives
proprioceptive input via the
mandibular nerve from the muscles of
mastication and from pressure
receptors in the periodontal ligaments
of the teeth.
2. Special Visceral Efferent (SVE)
innervates the muscles of mastication
(masseter, pterygoids, and temporalis
muscles), tensor tympani and some
other muscles.

26. Facial Nerve (n. VII)
The (SVE) Fibers from the motor nucleus of
facial nerve innervate the muscles of the
2nd
branchial arch; muscle of facial
expression and stapedius (moves stapes
bone) muscles.
The (GVE) Parasympathetic preganglionic
fibers from the superior salivatory
nucleus make synaptic connections with
postganglionic neurons in the
pterygopalatine and submandibular
ganglia; these fibers stimulate the
lacrimal, nasal, oral, submandibular and
sublingual glands, and blood vessels.
The GSA input from the external acaustic
meatus and a small area in the back of
the auricle these fibers pass to the
sensory nucleus of vagus
The SVA (taste) input from the anterior two-
thirds of the tongue terminate in the
nucleus solitarius

28. Vestibulocochlear Nerve (n.VIII)
It contains special somatic
afferent fibers (SSA)
• The cochlear nerve
concerned with hearing,
consists of fibers of bipolar
neurons with cell bodies in
the spiral ganglion.
• The vestibular nerve
concerned with equilibrium
and orientation of the head in
space, consists of fibers of
bipolar neurons with cell
bodies in the vestibular
ganglion.

29. Glossopharyngeal Nerve (IX)
The GVA input from the palatine, tonsillar, and pharyngeal
regions and from the carotid sinus and carotid body is
conveyed to the nucleus solitarius.
The SVA input (taste) from the posterior third of the tongue
is relayed via to the gustatory portion of the nucleus
solitarius, which is located at its rostral end.
The GSA afferents from the tympanic cavity and external
auditory meatus terminate in the spinal trigeminal nucleus.
The SVE (branchiomotor) from the nucleus ambiguus
innervate the stylopharyngeal muscle of the 3rd
pharyngeal
arch (elevates upper pharynx).
The GVE (preganglionic parasympathetic) component from
the inferior salivatory nucleus is relayed via the otic
ganglion to the parotid gland.

31. Vagus Nerve (X(
The GVA input from the respiratory system (larynx, trachea, and
lungs), cardiovascular system (carotid sinus and body, heart, and
various blood vessels), gastrointestinal tract, and dura mater in the
posterior fossa. The peripheral processes extend from the organs to
the cell bodies located in the inferior ganglion of the vagus; the
central processes terminate in the nucleus solitarius.
The SVA (taste). Their peripheral processes originate in the most
posterior part of the tongue and epiglottis and extend to cell bodies
in the inferior ganglion adjacent to the medulla; central processes
terminate in the gustatory portion of the nucleus solitarius.
The GSA component consists of fibers from the tympanic cavity
(middle ear) and the external auditory meatus (with cell bodies in
the superior ganglion) that terminate in the spinal trigeminal
nucleus.

32. The GVE component consists of preganglionic
parasympathetic fibers from the dorsal vagal
nucleus that project to terminal ganglia close to
their target structures. From there, postganglionic
neurons go to the cardiovascular, respiratory, and
gastrointestinal systems of the thorax and
abdomen.
The SVE output takes origin from lower motor
neurons in the nucleus ambiguus that innervate the
voluntary muscles of the soft palate, pharynx, and
intrinsic laryngeal muscles

35. Accessory nerve
The accessory nerve consists of
two roots, spinal and cranial. The
spinal root innervates the
ipsilateral sternomastoid and the
upper half of the trapezius
muscles.
• SVE
• The fibers of the cranial root
originate from the nucleus
ambiguous (SVE(, and joining the
branches of the vagus nerve which
innervates the intrinsic laryngeal
muscles

37. Hypoglossal Nerve (XII(
1. GSE
Lower motor neurons
originating in the hypoglossal
nucleus (GSE) innervate the
ipsilateral tongue musculature,
including the intrinsic muscles
and the genioglossus,
styloglossus, and hyoglossus
muscles.