Know about the visual pathway. All the nerves related to the eye. 4 cranial nerves - optic, occulomotor, trochlear abducens. Nucleus of cranial nerves

1. THE
OPTIC,OCULOMOTOR,TROCHLEAR,
ABDUCENT CRANIAL NERVES. THE
VISUAL TRACT .

3. Function: transfer visual information from the retina to the vision centers of the brain
via electrical impulses.
Pathology: vision loss or even incomplete blindness(amaurosis).

6. THEOPTICNERVE
The II paired cranial nerve.
Is a specific sensitivity nerve formed of axons of ganglionic cells of retina that join in the area of the optic disc
(physiological cup). This nerves penetrates the tunics of the eyeball and enters the cranial cavity via optic
canal.
The two nerves join in the area of tuber cinereum to form incomplete decussation at the optic chiasm where
only fibers that arise from the medial portions of both retinas decussate. The optic chiasm actually gives rise to
the optic pathway.
The fibers past the optic chiasm and then go to the optic tract where it contains both contralateral and
ipsilateral fibers.
The axons from the lateral geniculate body and pulvinar go to the cortical end of visual analyzer which is within
the marginal area of the calcarine sulcus of occipital lobe.
The axons of superior colliculi run to the parasympathetic nuclei of the oculomotor nerve thus parasympathetic
fibers running to the intrinsic muscles of eye(sphincter pupillae, ciliary muscle).
The above circuit constitutes the pupillary reflex arc. Apart from this, the superior colliculi join the tectospinal
tract for the instant response to sudden sound stimuli(start reflex).

9. THE OCULOMOTOR NERVE
The III cranial nerve. Mixed nerve consisting of motor and parasympathetic fibers.

10. THE NUCLEI
Has two nuclei
Nucleus of oculomotor nerve: in the midbrain at the level of superior
colliculi.
Accessory nucleus of oculomotor nerve: parasympathetic nucleus
medially from motor nucleus.

11. TOPOGRAPHY
Arises from medial surface of the
cerebral peduncle and move along
the external wall of cavernous sinus
and enters the orbit via superior
orbital fissure. Becomes evident in
the area of interpeduncular fossa.
Within the orbit, the nerves gives
superior and inferior branch. The
superior branch supplies the
superior rectus and levator
palpebrae while inferior branch
supplies inferior and medial rectus,
inferior oblique.

12. PARASYMPATHETIC FIBERS
comprises of preganglionic fibers from the
accessory nucleus of oculomotor nerve.
Upon entering the orbit, these fibers part
the motor fibers and reach the ciliary
ganglion which is laterally from the optic
nerve. The ganglion gives off the
postganglionic fibers that join the short
ciliary nerves and supply the ciliary muscle
and sphincter pupillae.
FUNCTION: responsible for eyeball and
eyelid movement.
Pathology: injury result in squint,
depression of superior eyelid(ptosis),
dilation of the pupil and accommodation
impairment.

13. THE TROCHLEAR NERVE

14. The IV paired cranial nerve and purely motor. It’s
nucleus resides in the tegmentum of cerebral
peduncle on the level of inferior colliculi. Nerve arises
laterally from the frenulum of superior medullary
velum on the dorsal surface of brainstem. On it way
to destination point, it loops around the cerebral
peduncle and move along the lateral wall of
cavernous sinus and enters the orbit via superior orbit
fissure to supply the superior oblique muscle.
Function: The superior oblique muscle controls the
downward movement of eyeball

15. THE
ABDUCENT
NERVES
The VI cranial nerves and purely motor that supplies one extrinsic
muscle of eyeball. The nucleus of abducens nerve is in the
tegmentum of pons on the level of facial colliculus. The nerve
arises from the the medullopotine sulcus between the pons and
olives and move along the cavernous sinus running laterally from
the the internal carotid artery. The nerve enters the orbit via inferior
orbital fissure and terminate within the lateral rectus.

16. Function: controls movement of the lateral rectus muscle responsible for outward gaze.

18. THE
PATHWAYS
OF VISUAL
ANALYZER

19. The retina comprises three linked
layers of the nerve cells that
accept light stimuli and transmit
them to the brain.
1. The rods and cones
a. The cones mostly occupy the
area of macula.
b. The rods are scattered all
around the retina .
2. The bipolar neurons
3. The ganglionic neurons