Exam 1: Unit II: CNs Related to Smell, Vision, and Ocular Movement (I,II,III,IV,VI) Flashcards
Where are olfactory neurons found?
in olfactory epithelium lining superior part of the nasal cavity and a thin layer of mucus covers this epithelium
What are the two neurons involved in the pathway for CN I (olfactory N.)?
- Primary sensory neurons called olfactory neurons (bipolar)
- Secondary sensory neurons called Mitral Cells
What are olfactory neurons supported by? And what do olfactory “hairs” function as?
supported by “supporting cells” and olfactory “hairs” function as receptors
The axons (central processes) of olfactory neurons are collected into __________ that convey information to the ________.
10-20 olfactory nerves; convey info to olfactory bulb
T/F. Olfactory neuron axons are myelinated by Schwann cells.
False, they are covered by Schwann cells (every PNS neuron is), but they are UNmyelinated
What do olfactory nerves pass through and what do they synapse on? What are formed at the synapse?
pass through cribiform plate of ethmoid bone and synapse on dendrites of mitral cells, where synaptic glomeruli are formed
Where are the cell bodies for Mitral cells located?
in olfactory bulb
T/F. Mitral cells relay information anterior via the olfactory tract.
False. They relay information posterior via the olfactory tract
Where do mitral cells split into medial and lateral olfactory striae (branches)?
at the anterior perforated substance
What is the path for medial stria fibers of the mitral cell?
cross midline via anterior commissure and travel to opposite olfactory bulb to synapse on other mitral cells
What is the path for lateral stria fibers of the mitral cell?
carry info to primary olfactory cortex; containing the periamygdaloid and prepirifrom area, including uncus (BMA 34)—on medial aspect of temporal lobe
~there is a secondary olfactory cortex
What does the secondary olfactory cortex contain?
entorhinal area, located in parahippocampal gyrus (BMA 28)
When testing smell of a patient what does a clinician need to take into consideration?
- make sure no allergies
- cover patients eyes
- use one nostril at a time
- good options: mint, PB
What is the word for loss of smell or lack of smell?
ansomia
What are some other clinical considerations when it comes to the olfactory system?
- ansomia
- skull fractures from trauma
- CSF leakage–> halo sign
What are the only fibers that are contained in the anterior commisure?
the medial stria fibers from the mitral cells, part of the olfactory tract
Do we segregate smell?
NO. Due to the medial strai fibers from the mitral cells in the olfactory tract crossing over to other olfactory bulb
What are two other pathways associated with smell?
- Terminal Nerve
2. Vomeronasal Nerve
T/F. The vomeronasal Nerve is very well developed in humans.
False. It is poorly developed in humans; thought to be important in tracking prey
What structure does the Terminal Nerve arise from? What is its function?
from nasal septum– has autonomic fxn (“smell fear”)
What are the three layers (tunics) of the eye?
Outermost = Fibrous tunic Middle = Vascular tunic Innermost = Retina of (Nervous tunic)
What does the Fibrous layer of the eye consists of?
- sclera (white)
- cornea (clear)
(outermost layer)
What does the Vascular layer of the eye consists of?
- ciliary body
- iris
- choroid
(middle layer)
What are the 10 layers of the retina (nervous tunic) from when light hits and info carried out of eye?
(light hits first)
- Pigmented layer
- Rod and Cone receptors
- External limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- Inner Nuclear layer
- Inner plexiform layer
- Ganglion cell layer
- Nerve fiber layer
- Internal limiting membrane
The pigmented layer of the retina is adjacent to what structure?
the choroid
What are the photosensitive segments of the retina?
the rods and cones receptors
What does the outer nuclear layer of the retina contain?
rod and cone cell bodies
What occurs in the outer plexiform layer of the retina?
rods and cones synapse with bipolar cells
The inner nuclear layer of the retina contains cell bodies of what cells?
bipolar cells
What occurs in the inner plexiform layer of the retina?
bipolar cells synpase with ganglion cells
What is in the ganglion cell layer of the retina?
ganglion cell bodies
What does the nerve fiber layer of the retina contain?
retinal ganglion cell axons–> they are NOT myelinated
What is the internal limiting membrane of the retina?
is a glial boundary separating retina from vitreous body
What are the photoreceptors?
Rods and Cones
- distal end (called “outer segment”); closest to choroid
- is either cylindrical (cone) or tapered (rod)
What are the types of cones found in the retina? What is the function of cones?
Red, Green, Blue
- fxn = receive color info; require adequate light
Where are cones more concentrated in the retina?
toward the center; fovea centralis
What is the fovea centralis?
point of retina of clearest vision, where we focus light; CONES only!
What is the function of Rods? Where are they located in retina?
sense only light vs. dark (detect shades of grey)
No rods in fovea; periphery of retina = almost all rods
Describe some facts on color blindness.
- differ forms
- most sex-linked, recessive trait on X chromosome
- MC in males
- due to lack of certain cones or number of
Depolarized photoreceptors relay info to bipolar cells by synapsing in what layer?
the outer plexiform layer
Bipolar cells in the retina are found in what layer?
inner nuclear layer
In the retina, what is the path of just the cells from when light hits them to where info is carried out of eyeball?
rod/cone photoreceptors –> bipolar cells –> ganglion cells that synapse in 1 of 3 places
In the retina, what cells do bipolar cells relay info to? Where does this synapse occur?
to ganglion cells; in inner plexiform layer
Where do axons from the ganglion cells (of the retina) located and where do they go/ what is the path to when they reach the optic chiasma?
axons in Nerve Fiber layer; go toward optic disc –> then leave eyeball and carried to optic nerve –> enter skull via optic canal –> unite to form optic chiasma
Are the nerve fiber layer axons myelinated?
No
Are optic nerve axons myelinated? If so, what cells myelinate them?
YES; myelinated by interfasicular oligodendrocytes
Are the axons of ganglion cells PNS or CNS? What about the optic nerve fibers?
ganglion cells = PNS
optic nerve = CNS