This document discusses cranial nerves III, IV, and VI. It provides details on: 1. The functional components, origin nuclei, course, and functions of CN III, including its motor and parasympathetic roles. 2. The unique features and course of CN IV. 3. The origin, course, and role in lateral eye movement of CN VI. 4. Clinical signs that result from damage to different parts of these cranial nerves, such as diplopia and ptosis.

1. Cranial nerve III, IV and VI
To MBBS 2nd year
05-04-2016
Dr. Laxman Khanal (Asst. Professor)
Department of Anatomy, BPKIHS

2. How to study the cranial nerves ??
• Know the position of nuclei and their functional components.
• Know the site of attachment of cranial nerve in brain stem.
• Course of cranial nerve.
• Functions of cranial nerves.
• Clinical correlation of nerve damage with the signs and symptoms.

5. Functional component of motor nerves
1. GSE- supply somatic skeletal muscle.
2. GVE- parasympathetic supply
3. SVE- supply branchial muscles
(LR 6 SO4)3GVE:
Supply smooth muscles
1. Sphincter pupillae
2. Dilator pupillae
3. Ciliary muscle
• GSE: for 3/4/6
• GVE: 3
 3 has GSE + GVE
 4/6 have GSE only

6. Intraocular muscles (smooth muscles)
1. Constrictior pupillae- parasympathetic innervation
2. Dilator pupillae- sympathetic innervation
3. Ciliary muscle- parasympathetic innervation

7. Cranial nerve III
• Functional components: GSE and GVE
• Origin (nuclei): midbrain @ the level of superior colliculus
• Nuclei: two in number
1. Main motor nucleus- GSE
2. Parasympathetic nucleus (Edinger Westphal Nucleus)-GVE

9. TS midbrain @ SC
Oculomotor nerve nuclei
Cross section
of 3rd nerve

10. Interpeduncular
fossa
Lateral wall of
cavernous sinus
Superior orbital
fissure
Orbital cavity
Course of oculomotor nerve

11. - Motor function (GSE)
- Parasympathetic function (GVE)
C
(LR 6 SO4)3
1. Sphincter pupillae
2. Ciliary muscle

12. Direct and consensual light reflex
c
Cilliary
ganglion
Short ciliary nerve
Pupillary constriction of
both eyes in response to the
light shone in one eye.

13. Accommodation reflex
c
When eyes are directed from distance to near object.
1. Convergence of ocular axis occurs (contraction of MR).
2. Lens thickens to increase refractive power (contraction of ciliary muscle)
3. Pupil constrict to restrict the light waves to the thickest central part of the
lens (contraction of constrictor pupillae muscle).

14. c
c
c
Frontal eye field
Medial
rectus
Argyl Robertson Pupil (ARP)
Damage of pretectal nucleus
abc

16. M
P
All extraocular muscles (+ LPS)
except LR and SO
C
G
Constrictor pupillae
Ciliaris muscle
LR
SO
• Eye looks laterally and downward
and leads to Diplopia.
• Ptosis
• Mydriasis
• Loss of Accommodation
External
ophthalmoplegia
Internal ophthalmoplegia

17. Trochlear nerve
The trochlear nerve has several features that make it unique from the
other cranial nerves.
• It is the only nerve to exit from the dorsal surface of the brain.
• It is the only nerve in which all the lower motor neuron fibers
decussate.
• Has the longest intracranial course.
•Has the smallest number of axons.
c
c

19. Course of trochlear nerve
• Dorsal surface of midbrain
• Lateral wall of cavernous sinus
• Enter the orbit through sup orbital fissure
• Supply superior oblique( downward and lateral movement)
Diplopia on looking
downward (vertical
diplopia).

20. Trochlear nerve

21. Abducent Nerve
• It is small cranial nerve,
arising from the single
nucleus located just
beneath the facial colliculus
in Pons.
• Nerve emerge at the level of
Ponto-medullary junction.
• It is often the first nerve
compressed when there is
any rise in intracranial
pressure.

22. 66
7 7
MLF

23. Course of Abducent nerve
Internal strabismus

24. LR

25. Internal strabismus External strabismusStraight view
LR is paralysed MR is paralysed

26. Q. Constrictor pupillae muscle is supplied by which nucleus of
oculomotor nerve?
Q. Name the functional component of 3rd nerve supplying
constrictor pupillae?
Q. Lateral rectus is supplied by which cranial nerve?
Q. A person has accommodation reflex intact but no pupillary light
reflex; where must be the lesion?
EWN
GVE
6th
a. EWN b. motor nucleus of 3rd nerve
c. Pretectal nucleus d. optic nerve

27. Which nerve is helping
him?
He is facing diplopia when
looking down the stairs.
Which nerve is not
functioning well?
Fourth
• Prevent from fall
• Prevent from fail