CN I found in olfactory epithelium lining ….
Superior part of nasal cavity
Sup. Nasal concha only, not middle or inf.
T/F. Olfactory N are myelinated
F. Unmyelinated but they are covered by schwann cells
Olfactory tract fibers split into medial and lateral olfactory striae at the ______________________.
Anterior perforated substance
Medial stria fibers cross midline via the
Anterior commissure
Lateral stria fibers carry info to the:
Primary olfactory cortex; on the medial aspect of the temporal lobe
Periamygdaloid and prepiriform area
–including the uncus (34) and entorhinal area (28)
Alternative olfactory pathways
Terminal nerve & Vomeronasal nerve
Terminal nerve pathway
From receptors on nasal septum (autonomic)
Vomeronasal nerve pathway
Poorly developed in humans
Important for tracking prey
3 layers of the eye
Outermost layer = fibrous tunic Sclera, cornea Middle layer = vascular tunic Ciliary body, iris, choroid Innermost layer = retina 10 layers
Retina layers
- Pigmented layer
- Photosensitive outer segments of rods and cones
- External limiting membrane
- Outer nuclear layer (rod/cone cell bodies)
- Outer plexiform layer (synapse on bipolar cells)
- Inner nuclear layer (bipolar cell bodies)
- Inner plexiform layer (synapse on ganglion cells)
- Ganglion cell layer (bodies)
- Nerve fiber layer (retinal gang axons -not myelinated)
- Internal limiting membrane (separates retina from vitreous body)
Cones -3 types and where concentrated
Red, blue, green
More concentrated toward center of retina (fovea centralis = point of clearest vision)
Ganglion cell axons (nerve fiber layer) -> \_\_\_\_\_\_\_\_\_ -> Optic nerve -> \_\_\_\_\_\_\_\_\_-> Optic chiasma
- Optic disc
2. Optic canal
Are optic nerve axons myelinated?
Yes.
Not myelinated inside eye. Axons leave eye at optic disc and become myelinated and form optic nerve.
What cells form CNS myelin
Interfascicular oligodendrocytes
In the optic chiasma, fibers from which side of the retina cross?
Medial (nasal) side cross
Lateral (peripheral) side do not cross
Optic tract travels around cerebral peduncles and fibers synapse on 1 of 3 nuclei or termination:
1: Majority synapse in LATERAL GENICULATE BODY and are relayed to cerebral cortex in the occipital lobe (BDMN 17)
2: Superior colliculus - info relayed to tectospinal tract (SCM & Traps)
3: Pretectal nucleus of midbrain - fibers deal with light reflexes
Visual Reflexes
Direct and Consensual light reflexes
Accommodation reflex
Corneal reflex
Convergence
Direct and consensual light reflexes
Flashlight in eye to see both eyes contract
Accommodation reflex
Switching focus
Corneal reflex
Touch eye with cottonball
Convergence
Cross eyes
Oculomotor nuclei receive input from
- BDMN 8
- Superior colliculus
- Medial longitudinal fasciculus
Somatic nuclei of origin, located in periaqueductal gray matter
Oculomotor nuclei
Oculomotor axoxs travel anteriorly through the Red nucleus and exit CNS in (apparent origin)
The interpeduncular fossa (into the cistern)
Oculomotor nerve enters eye socket and splits into sup and inf rami, supplying …
Superior ramus supplies superior rectus and levator palpebral superioris
Inferior ramus splits into 3 branches:
Medial branch supplies medial rectus
Central branch supplies inferior rectus
Lateral branch supplies inferior oblique
Nerves leaving the ciliary gangion also carry sypathetic and somatic sensory fibers picked up from …
The opthalmic nerve V1 passing through the ganglion without synapsing
What parts of the brain send axons to the trochlear nucleus?
BDMN 8, Sup colliculus, and Medial longitudinal fasciculus
Abducens nucleus is located…
In the caudal part of the pons, at the floor of the rhomboid fossa
Abducens nerve receives info from
Same as CN III & IV
BDMN 8, SC, MLF
What is Strabismus
Eyes not pointing at the same thing
Internal Strabismus
Eyes cross (converge)
External strabismus
Eyes directed away from each other (diverge)
Diplopia
Double vision
Ptosis
Eyelid droops due to weakness of levator palpebrae superioris. CN III lesions may be the cause
Oculomotor paralysis
External ophthalmopegia:
- External strabismus; effected eye deviates down and out
- Diplopia
- Ptosis
Internal ophthalmopegia:
- Inability to constrict pupil
- Loss of light reflex
- Loss of accommodation reflex
Etiologies of oculomotor paralysis
Uncal herniation,
PCA anneurysm (post cerebral aneurysm)
Diabetes
Trochlear paralysis
Internal strabismus. Inability to look down (slight converging when looking down)
Rare
Abducens paralysis
MC
Internal strabismus + displopia
Internuclear ophthalmoplegia
Lesion to MLF
Nystagmus when abducting eye
Practice table 1 pg 183
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