Cranial and spinal nerves

Medical neuroscience

1. Cranial and
spinal
nerves
Domina Petric, MD

2. Cranial nerves
I.

3. Olfactory nerve (I.): sense of
smell
It is a set of fine axons that run from the nasal
epithelium to the olfactory bulb so it is not really
a nerve, but part of the brain.
Those axons run through the ethmoid bone
(cribriform plate).

4. Optic nerve (II.): vision
Grows out from retinal ganglion cells (inner layer of
the retina).
Two optic nerves make optic chiasm.
It is part of the brain.

5. Oculomotor nerve (III.): eye movements,
pupillary constriction and accommodation;
muscles of eyelid
–Emerges from the interpeduncular fossa in the midbrain
(mesencephalon).
–Somatic motor component innervates muscles of the
eyeball (not all of them) and muscle that elevates the
eyelid.
–Visceral motor component is parasympathetic
preganglionic outflow that is involved in constricting
the pupil.

6. Trochlear nerve (IV.): eye movements
(intorsion, downward gaze)
–Emerges from the dorsal aspect of the brain stem
(midbrain).
–It is only cranial nerve that exits on the dorsal side of
the central nervous system.
–It has only somatic motor outflow that innervates
superior oblique muscle of the eyeball (inward and
downward gaze).

7. Trigeminal nerve (V.): motor and sensory, somatic
sensation from face, mouth and cornea; muscles
of mastication
–Only nerve emerging from the ventro-lateral
aspect of the pons.
–Branchial motor component is for muscles of
mastication.
–General somatic sensory component for
somatic sensation from face, mouth and
cornea.

8. Abducens nerve (VI.): eye movements
(abduction or lateral movements)
–Emerges from the junctional region
between pons and medulla oblongata,
close to the midline.
–Single somatic motor output for lateral
rectus muscle of the eyeball.

9. Facial nerve (VII.): controles the muscles of facial
expression, taste from anterior tongue, lacrimal
and salivary glands
–Emerges from the junctional region between pons and medulla
oblongata.
–Branchial motor component supplies the muscles of facial expression.
–Parasympathetic outflow for the numerous glands in the cranial region:
lacrimal and salivary glands (exept for the parotid gland).
–Special visceral outflow (sense of taste) from anterior two thirds of the
tongue.
–General somatic sensory component: small patch of skin in the ear.

10. Vestibulocochlear nerve (VIII.): hearing,
sense of balance
–Emerges from the junctional region between
pons and medulla oblongata.
–It is the most lateral nerve emerging from the
junctional region.
–Special sensory nerve: hearing (cochlea) and
sense of balance (labyrinth).

11. Glossopharyngeal nerve (IX.): sensation from posterior
tongue and pharynx, taste from posterior tongue, carotid
baroreceptors and chemoreceptors
–Emerges from the medulla oblongata.
–Branchial motor component for the innervation of the muscles around the
pharynx.
–Parasympathetic outflow for the parotid gland.
–Special visceral sense of taste from the posterior one third of the tongue.
–General visceral sensory output from the carotid bodies which are important
for regulating blood pressure, cardiac output and respiration rate.
–Somatic sensory component:small patch of skin from the external ear.

12. Vagus nerve (X.): autonomic functions of
gut, sensation from larynx and pharynx,
muscles of vocal cords, swallowing
–Emerges from the medulla oblongata.
–Branchial motor component provide innervation to muscles of the posterior
pharynx and the region of the larynx.
–Parasympathetic outflow for the viscera in the thorax and in the upper part of the
abdomen.
–Special visceral sensation of taste from some taste buds in the posterior part of
the oral cavity.
–Visceral sensory signal for regulation of cardiovascular system (aortic arch).
–Somatic general sensory innervation to a patch of skin around the external
auditory meatus.

13. Spinal accessory nerve (XI.):
shoulder and neck muscles
–Emerges from the medulla oblongata.
–Branchial motor output for the upper
part of the trapezius muscle and the
sternocleidomastoid muscle.

14. Hypoglossal nerve (XII.):
movements of tongue
–Emerges from the medulla
oblongata, between medullary
pyramid and olive.
–Somatic motor output for tongue
muscles.

15. Cranial nerves
http://teachmeanatomy.info/wp-
content/uploads/Brain-stem.png

16. Cranial nerves nuclei in the
brain stem
–4 somatic motor nuclei
–4 branchial motor nuclei
–4 parasympathetic motor nuclei
–4 sensory nuclei

17. Somatic motor nuclei
–Oculomotor nucleus
–Trochlear nerve nucleus
–Abducens nucleus
–Hypoglossal nucleus

18. Branchial motor nuclei
–Trigeminal motor nucleus
–Facial nucleus
–Nucleus ambiguus (IX. and X.)
–Accessory nucleus

19. Parasympathetic nuclei
–Endinger Westphal nucleus (III.)
–Salivatory nuclei (VII. and IX.)
–Nucleus ambiguus (IX. and X.)
–Dorsal motor nucleus of vagal nerve
(XI. and XII.)

20. Sensory nuclei
–Nucleus of the solitary tract for special visceral and general
visceral sensation (VII., IX. and X.): rostral division is for the taste
and caudal division for visceral sensation.
–Trigeminal nuclear complex for the somatic (general) sensory
output (V., VII., IX. and X.): mechano-sensation, pain and
temperature sensitivity.
–Cochlear nucleus
–Vestibular nucleus

21. Cranial nerve
nuclei
http://www.instantanatomy.net/di
agrams/HN139.png

22. Spinal nerves
II.

23. Spinal nerves
–8 pairs of cervical nerves
–12 pairs of thoracic nerves
–5 pairs of lumbar nerves
–5 pairs of sacral nerves
–1 coccygeal nerve

24. Two spinal enlargements: motor
and sensory output
cervical enlargement (arms)
lumbosacral enlargement (legs)

25. Cauda equina
(horses tail)
http://www.rdehospital.nhs.uk/im
ages/services/PEOC%20Spinal%20U
nit/cauda%20equina.JPG

26. Spinal roots
Ventral root is a motor root and sends signals to
striated muscles.
Dorsal root is a sensory root.
BUT spinal nerves can be mixed nerves, with motor
and sensory axons.

27. http://www.spinalhub.com.au

28. Sympathetic chain

29. Literature
–https://www.coursera.org/learn/medical-
neuroscience/lecture: Leonard E. White,
PhD, Duke university.
–TeachMeAnatomy. Com
–www.instantanatomy.net

30. Literature
–www.rdehospital.nhs.uk
–http://www.spinalhub.com.au