quiz CN 1 And 2 Flashcards
What is Cranial nerve 1?
Olfactory nerve
What kind of neuron is the olfactory neurons? And what type (uni/bi)
It is a primary sensory neurons
Bipolar
Where are the primary sensory neurons for the olfactory neurons lie?
Found in olfactory epithelium lining superior part of nasal cavity
What covers the olfactory epithelium?
A thin layer of mucus
Olfactory neurons are supported by what kind of cells
Supporting cells
What do olfactory “hairs” function as?
Function as receptors.
Central processes (axons) for olfactory nerves are conveyed where and how many are there
Axons are collected into 10 to 20 olfactory nerves that convey information to the olfactory bulbs
Are olfactory neuron axons myelinated?
They are unmyelinated, but covered by Schwann cells
Where do olfactory nerves pass to? (Pathway)
Pass through the cribiform plate, part of the ethmoid bone. They enter the olfactory bulb and synapse on dendrites of mitral cells. Synaptic glomeruli are formed at the synapses
How many neurons is this pathway for olfactory?
2 neuron pathway
What cells are the secondary sensory neurons in the olfactory pathway
Mitral cells
Where are the mitral cells located?
In the olfactory bulb
Mitral cells relay information from where?
Relay information posterior via the olfactory tract
Where do the fibers split for the mitral cells?
At the anterior perforated substance, the tract fibers split into medial and lateral olfactory striae
Where do Medial Stria fibers go?
Cross midline via anterior commissure and travel to opposite olfactory bulb
Do we segregate smell?
No
Where do the lateral stria fibers go?
Carry information to the primary olfactory cortex; periamygdaloid and prepiriform area, including the uncus (Brdmn 34) on the medial aspect of the temporal lobe
Lateral stria fibers also go to the secondary olfactory cortex, what is included in this
Entorhinal area, located in parahippocampal gyrus (Brdmn 28)
What Brodmann areas are included in the olfactory pathway
34, 35, 28
What kind of traumas can make patients lose smell temporarily?
Head traumas
What test can be done to perhaps test for dementia
Peanut butter test
What is another name for loss of smell?
Anosmia
Is it possible to not be born with CN 1?
Yes, but very rare
If you have CSF leakage in the nose, how can you test if it truly is?
Halo sign test
What is the terminal nerve (other pathway)
Info from receptors on nasal septum
Autonomic in function
What is the vomeronsal nerve (other pathway)
Poorly developed in humans, believed to be important in tracking prey
What is the name for cranial nerve 2
Optic nerve
The eye is a sensory organ of vision. What three layers make it up?
Outermost layer - fibrous tunic
Middle layer - vascular tunic
Innermost layer - retina (it has ten layers)
What does the fibrous tunic consist of
Sclera - white
Cornea - clear
What does the vascular tunic consist of
Ciliary body
Iris; color part, made up of two muscles
Choroid
The optic nerve is a how many neuron pathway
It is a 4 neuron pathway
What are the ten layers of the retina? Outside to in
Pigmented layer Photosensitive outer segments External limiting layer Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fiber layer Internal limiting membrane
What is the pigmented layer adjacent to?
Choroid
What doesn’t eh photosensitive outer segment contain?
Rods and cones
Outer nuclear layer contains what
Rod and cone cell bodies
Outer plexiform layer contains what
Rods and cones synapse with bipolar cells here
Inner nuclear layer contains what
Cell bodies of bipolar cells
Ganglion cell layer contains what
Ganglion cell bodies
Nerve fiber layer contains what
Retinal ganglion cell axons. These fibers are NOT myelinated
What is the internal limiting membrane
A glial boundary separating the retina from the vitreous body
What part of the photoreceptors is either cylindrical(rod shaped)or cone shaped (tapered)
Distal end of the photoreceptor
What are the three types of cones
Red, green blue
Cones do what?
Receive color information and help with clarity of image
Do cones require light?
Require adequate light to function best (the more the better)
Where are cones mostly concentrated?
More concentrated toward center of retina(fovea)
What do rods do?
Sense only light vs dark
Are their rods in fovea?
No rods in fovea, periphery of retina is almost completely composed of rods
Color blindness is what kind of condition
Multiple forms mostly sex linked
When depolarized, what do photoreceptors do?
Relay information to bipolar cells by synapsing in the outer plexiform layer.
Where are bipolar cell bodies found?
In the inner nuclear layer
Where do the bipolar cells relay information to?
The ganglion cells, the synapse occurs in the inner plexiform layer
Axons from ganglion cells are conveyed where?
Conveyed in the nerve fiber layer toward the optic disc. These axons are carried in the optic nerve after leaving the eyeball. The optic nerves enter the skull through the optic canal and untie to form the optic chiasma
Are nerve fiber layer axons myelinated
No
Are optic nerve axons myelinated
Yes
What cells form myelin for the optic nerve axons
Infasicular oligodendrocytes
How do the fibers run in the optic chiasma
Fibers from medial (nasal side) of each retina will cross, while fibers from lateral (peripheral side) of the retina will not cross. Fibers split to form the optic tracts
Where does the optic tract travel around?
Travels around the cerebral peduncles and fibers synapse on one of three nuclei of termination
What are the nuclei of termination and their characterisitics
Majority synapse in lateral geniculate body and are relayed to the cerebral cortex in the occipital lobe (17)
Fibers synapsing in the superior colliculus where information is relayed to the tectospinal tract
Some fibers synapse in the pretectal nucleus of the midbrain. These fibers deal with light reflexes
What two muscles are influenced by the tectospinal tract
Sternocleidomastoid
Trapezius
If you have a lesion in the optic nerve, what happens?
Blind in one eye
If you have decussating fibers of the optic chiasma being cut or lesioned, what happens
Peripheral vision gone
If you have a lesion in the optic tract, what happens
Half of vision field gone
What visual reflexes does CN 2 deal with
Direct and consensual light reflexes
Accommodation reflex
Corneal reflex
Convergence
What does direct and consensual light reflex do?
One eye will constrict while other dilates
What does accommodation reflex do?
Going from far sight to something close in view, lens becomes more convex to focus on near objects
What does corneal reflex do
Soft cotton balls, lightly touch cornea, patient should pull away and blink
What does convergence do
Pulling eyes together or inward
