1. Cranial Nerves
Prof. K. Sivapalan

2. Classification of Peripheral Nerves.
Somatic efferent- fibers supplying striated muscles of limbs, body wall, eyes and tongue. These are found in spinal nerves and cranial nerves- 3, 4, 6 and 12.
General visceral efferent- fibers that supply smooth muscles and glands. Autonomic fibers- cranial nerves 3, 7, 9 and 10 and spinal nerves T1-L2, S2- S4.
Special visceral efferent- fibers supplying skeletal muscles developed from branchial arch mesoderm - muscles of the face, mastication, pharynx and larynx. Found in cranial nerves 5, 7, 9, 10, and 11.
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Cranial Nerves

3. Classification of Peripheral Nerves ctd.
General somatic afferent- exteroceptive and proprioceptive fibers. Spinal nerves and cranial nerve 5.
Special somatic afferent- vision, hearing and equilibrium. Cranial nerves 2 and 8
General visceral afferent- fibers that carry sensations from viscera. Autonomic fibers-cranial nerves 3,7,9 and 10 and spinal nerves T1-L2, S2- S4.
Special visceral afferent- fibers carrying taste. Cranial nerves 7,9 and 10
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Cranial Nerves

4. Development of Cranial Nerves
During development, cranial nerve nuclei are arranged as in spinal cord
Neurons of afferents in dorsal or alar lamina and efferrents ventral or basal lamina.
Visceral efferents and afferents between the above.
Special efferents and afferents are placed between the general somatic and general visceral.
Formation of the fourth ventricle displaces the alar laminar laterally and the neurons span out.
Also columns of neurons in certain areas disappear and the remaining become discrete nuclei.
Some nuclei maintain the original place and the others migrate deeper into brain stem.
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Cranial Nerves

5. Olfactory Nerve Special somatic afferent because of ectodermal origin.
In view of relationship with sense of taste, special visceral afferent.
Details later with sense of smell
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Cranial Nerves

6. Optic Nerve Special somatic afferent. Tract of brain and not nerve.
Details with vision.
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Cranial Nerves

7. Oculomotor [3] Nucleus
Somatic efferent nucleus: in the upper part of the midbrain at the level of superior colloculus, ventral to aqueduct. Both side form single mass of gray.
General visceral efferent [Edinger – Westphal] nucleus: close to the somatic nucleus. Gives rise to fibers that supply sphincter papillae and ciliaris muscles after synapsing in ciliary ganglion
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Cranial Nerves

8. Trochlear [4] Nucleus
in the midbrain at the level of inferior colliculus, ventral to aqueduct.
Somatic efferent for superior oblique
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Cranial Nerves

9. Abducent [6] Nucleus
lower part of pons, floor of the fourth ventricle near midline.
Somatic efferent for lateral rectus of the eye
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Cranial Nerves

10. Facial [7] Nucleus
Branchial or special visceral efferent: lies in the lower part of the pons, supplies facial muscles
Superior salivary nucleus: general visceral efferent: in pons just above the junction with medulla.
Fibers relay in submandibular ganglion and supply submandibular and sublingual glands. ? part of parotid gland.
Fibers that relay pterygopalatine ganglion supply lacrimal gland.
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Cranial Nerves

11. Facial Nerve Fibers from Other Nuclei
Taste buds of the anterior two thirds of thetongue- special visceral afferent [from nucleus of the solitary tract].
General somatic afferent from a part of the skin of the external ear.
Fibers end in the trigerminal nucleus.
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Cranial Nerves

12. Vestribular & Cochlear [8] Nucleus
Special somatic afferent nuclei.
Dorsal and ventral cochlear nuclei are placed dorsally and ventrally to the inferior cerebellar peduncle, at the level of junction of medulla and pons.
The vestibular nuclei are medial, lateral, inferior and superior lying partly in medulla and pons
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Cranial Nerves

13. Glosopharyngial [9] Nucleus
Inferior salivary nucleus: general visceral efferent: in pons just above the junction with medulla.
Fibers relay in otic ganglion and supply the parotid gland.
Visceral efferent from nucleus ambiguous supply the stylopharyngeus muscle.
General visceral afferents carrying touch, pain, temperature from pharynx and posterior tongue, carotid sinus and carotid body to the solitary tract and reticular formation.
Special visceral afferents – taste from posterior third of the tongue to the nucleus of the solitary tract
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Cranial Nerves

14. Vagus [10] Nucleus
Dorsal [motor] nucleus- long nucleus in medulla, the upper end lies deep to vagal triangle in the floor of the fourth ventricle and the lower end is in the lateral part of the gray of the closed part.
General visceral efferent fibers supply the heart, lungs, bronchi, oesophagus, stomach, small intestine, large intestine up to right two thirds of the transverse colon through post ganglionic fibers in the organs.
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Cranial Nerves

15. Other Components of Vagus
General visceral afferents from pharynx, larynx, trachea, oesophagus, abdominal and thoracic viscera to nucleus of solitary tract.
Special visceral efferents- from nucleus ambiguous to muscles of the pharynx and larynx.
Special visceral afferents- taste from posterior most part of the tongue and epiglottis to nucleus of the solitary tract.
General somatic efferent- from the skin of the external ear to trigerminal nucleus.
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Cranial Nerves

16. Recurrent Laryngeal [11] Nucleus
Special visceral efferents- from nucleus ambiguous to muscles of pharynx, soft plate, and larynx.
From upper five cervical segments to trapezius and sternomastoid muscles
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Cranial Nerves

17. Hypoglossal [12] Nucleus
In medulla, elongated extending in open and closes parts. Somatic efferent.
General somatic afferent: proprioception from tongue
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18. Nucleus Ambiguous [9,10,11]
elongated column in open and closed parts of the medulla. [branchial or special visceral efferent]
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19. Nucleus of the Solitary Tract
General and special visceral afferent nuclei.
Elongated column in medulla. Upper part lies ventrolateral to the dorsal nucleus of the vagus and in the closed part of the medulla, it is dorsomedial to the dorsal nucleus of the vagus.
The lower end of both sides fuse- commissural nucleus. It receives general visceral sensations through glossopharyngeal [9] and vagus [10]nerves.
Taste fibers through facial [7] and glossopharyngeal [9] end in the upper part- gustatory nucleus.
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Cranial Nerves

20. Trigerminal [5] Nucleus
Motor nucleus lies in the upper pons, medial to the sensory nucleus.
Branchial or special visceral efferent to muscles of mastication
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Cranial Nerves

21. Sensory Nucleus of Trigerminal
Sensory nucleus is the general somatic afferent.
The superior sensory nucleus lies in the lateral pons; it is mainly concerned with proprioception, touvh and pressure sensations.
The spinal nucleus runs through the medulla into upper two segments of the spinal cord; it is mainly concerned with pain and thermal sensations. It also receives sensory fibers from 7,9 and 10th cranial nerves.
The mesencephalic nucleus extends cranially into the midbrain and lies lateral to the aqueduct. They are believed to receive proprioceptive fibers from muscles of mastication, eye balls, face, tongue and teeth.
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Cranial Nerves

22. Central Connections of Cranial Nerve Nuclei.
Somatic and special visceral efferents are similar to that of spinal anterior horn cells.
Nerves supplying lower half of the face and tongue get contralateral corticonuclear fibers.
Troclear nuclei are supplied by the ipsilateral but the nerve crosses as it leaves the brain stem.
All other nuclei get bilateral cortical control.
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Cranial Nerves