Download a)write short notes about the anatomy of optic nerve

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Neuroanatomy
a)write short notes about the anatomy of optic nerve
Optic Nerve (Cranial Nerve II)
Origin of the Optic Nerve
The fibers ol'the optic nerve are the axons orthe cells in the ganglionic layer of the retina. They converge
on the o(1tic disc and exit li'ol11 the eye. about 3 or 4 mm to the nasal side of its center. as the optic nerve
The libel's orthe optic nerve arc myelinated. but the sheaths arc j(JI'med li'om oligodendrocytes rather than
Schwann cells. sincc the optic nerve is comparable to a tract within the central nervous system,
The optic nerve leaves the orbital cavity through the optic canal and unites with the optic nerve ol'the
opposite side to larm the optic chiasma
Optic Chiasma
In the chiasma. the libel'S tj'om the nasal (rnedial) Iwlf of each
retina. including thc nasal half 01' the macula. cross the midline
and enter the optic tract or the o(1posite side. while the fibers
hom the tel11poral (lateral) half or each retina. including the
tem poral hal f of the macu lao pass posteriorly in the optic tract
of the same side
Optic Tract
The optic tract emerges I'rom the optic chiasma and passes
(1osterolaterally around the cerebral peduncle, Most of the
tibers no\\ terminate by synapsing with nerve cells in the
lateral geniculate body. which is a small projection from the
posterior part of the thalamus, A few of the tibers pass to the
prctectal nucleus and the superior colliculus of the
midbrain and are concerned with light retlexes
Lateral Geniculate Body
The lateral geniculate body is a small, oval swelling projecting
hom the pulvinar of the thalamus. It consists of six layers of
cells, on which synapse the axons of the optic tract. The axons of the nerve cells within the geniculate body
leave it to form the optic radiation
Optic Radiation
1
The fibers of the optic radiation are the axons of the nerve cells of the lateral geniculate body. The tract
passes posteriorly through the retrolenticular part orthe internal capsule and terminates in the visual cortex
(area 17)
Neurons of the Visual Pathway
Four neurons conduct visual impulses to the visual cortex:
(1) rods and cones, which are specialized receptor neurons in the retina;
(2) bipolar neurons, which connect the rods and cones to the gangl ion cells:
(3) ganglion cells, whose axons pass to the lateral geniculate body: and
(4) neurons of the lateral geniculate bodv. whosc axons pass to the cerebral cortex
b) describe the middle cranial fossa
consists of a small median part and expanded lateral parts
The median raised part is formed by the body of the sphenoid. and the expanded lateral parts rorm
concavities on either side. which lodge the temporal lobes o]'the cerebral hemispheres
It is bounded anteriorlv by the sharp posterior edges orthe lesser wings of the sphenoid
p~1'iL<;riorlv
by the superior borders 0 r the petrous parts 0 f the tem pora I bones.
l:'.!tcraLLY lie the squamous parts of the temporal bones. the greater wings orthe sphenoid. and the parietal
bones.
The floor oreach lateral part of the middle cranial fossa is larllled by the greater wing ol'the sphenoid alld
the squamous and petrous parts of the temporal bone.
c) enunlerate the nuclei of one of the followings:
- Vestibulocochlear Nuclei
Olivary Nuclear Complex
Vcstibulocochlear Nuclei
Vestibular comples:
(1) medial vestibular IlUCleUS
(2) inferior vestibular Ilucleus
(3) latcral vestibular nucleus
(4) superior vestibular nucleus
Cochlear nuclei:
(1) anterior cochlear nucleus
(2) posterior cochlear nucleus
Olivary Nuclear Complex
- The largest nucleus of this complex is the inferior olivary nucleus
- Smaller dorsal and medial accessory olivary nuclei also are present
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