Term
| What mechanical action happens in the eye when light hits? What electrical change does it cause? What about neurotransmitter levels? |
|
Definition
-Na+ channels in the rods and cones close because of a conformational change in retinol (Vit A derivative)
-Causes *hyperpolarization of rods and cones
-Results in *less neurotransmitter being released in the light than in the dark |
|
|
Term
| Go over the general pathway for info from the retina to the visual cortex? |
|
Definition
| -Rod/cone (pigment cell, not neuron)-->bipolar cell-->ganglion cell-->lateral geniculate nucleus (LGN)-->striate cortex (aka visual cortex) |
|
|
Term
| What is the pathway in terms of the nerve fiber names? |
|
Definition
| -Optic nerve--> Optic chiasm--> optic tract--> optic radiations |
|
|
Term
| What does contraction of the ciliary muscle produce? What controls it? |
|
Definition
-It runs circularly around the eye and produces the effect of *accommodation (thickening of the lens to see closer objects) as the suspensory ligaments relax
-It is stimulated by **parasympathetic control alone |
|
|
Term
| What are the three general layers of the eye? |
|
Definition
-Sclera, choroid, retina
-The choroid is the one with the blood vessels and non-visual nerves
-It serves to give nutrients to the retina; a concern in detachment of rods and cones in retina from it |
|
|
Term
| Which fibers desiccate at the optic chiasm? |
|
Definition
-Fibers from nasal retina (%60)
-End result is left visual field in both eyes being received in the right cortex, and vice versa |
|
|
Term
| Where all can the optic tract go and why? |
|
Definition
-Note; this is after the chiasm
-LGN; vision
-Pretectal area; light reflex
-Suprachiasmatic nucleus (hypothalamus); circadian rhythms
-Superior colliculi; reflex gaze |
|
|
Term
| How does superior vs. inferior visual field information differ? |
|
Definition
-The lower retina info (superior visual field) is the more *lateral optic radiation and goes through the **temporal lobe in **Meyer's loop before going back into the pareital lobe and terminating in the ***lingual gyrus
-The upper retina info (lower visual field) is more *medial, goes through the parietal only, and terminates in the **cuneus gyrus |
|
|
Term
| What is the gross anatomy of the visual cortex, and what is it's alternate name? What Brodmann area is it? |
|
Definition
-The *striate cortex is separated by the *calcarine sulcus into the cuneus gyrus (*sup.) and the lingual gyrus (*inf.)
-The parieto-occipital sulcus is the border of both
-Works out so that lower retina info goes to the lower gyrus (and rem. they are lateral and have Meyer's loop)
-Brodmann area 17 |
|
|
Term
| What do we call fibers going to and coming from the LGN? |
|
Definition
| -Optic tracts go in, optic radiations/visual radiations/geniculocalcarine tracts come out |
|
|
Term
| What are the effects of severing Meyer's loop on the left? What could produce it? |
|
Definition
-Right superior visual quadrant in each eye will be gone
-We call this **right homonymous superior quadrantanopia
-Homonymous refers to the fact that it's on the same side for each eye
-Optic radiation lesions like this produce no macular sparing
-A tumor or middle meningeal occlusion could produce this |
|
|
Term
| Then what would a left medial optic radiation lesion produce? |
|
Definition
| -Right homonymous inferior quadrantanopia |
|
|
Term
| What will lesions of the left straite cortex produce? |
|
Definition
-Right homonymous hemianopia with **macular sparing**
-The center of the visual field will still have vision
-Reason is, the most often cause of this is post. cerebral artery occlusion, but the macular cortex has a readily available collateral circulation (from middle cerebral a.)
-If it designed lingual gyrus only, it would be a superior deficit only etc. |
|
|
Term
| What do we call the darkening of vision associated with these lesions? |
|
Definition
|
|
Term
| What will unilateral optic nerve lesions produce when from MS? |
|
Definition
-Central scotoma in that eye
-Because the demyelination is typically of the deep nerves |
|
|
Term
| What deficit would we expect from a craniopharyngioma? |
|
Definition
-This is the pituitary tumor from Rathke's pouch
-It compresses the optic chiasm causing *bitemporal heteronymous hemianopia
-Can think of it as just cutting the optic chiasm |
|
|
Term
| What would you expect from an anterior communicating artery aneurism? |
|
Definition
-Anywhere on it localizes the pressure to the superior aspect of the optic chiasm
-So it will be like the craniopharyngioma, but only in the *inferior temporal fields (from sup. retina)
-Called bitemporal (heteronymous) inferior quandrantanopia |
|
|
Term
| Go over the pathway for the pupillary light reflex? |
|
Definition
-From retina to pretectal area--> efferent to **both Edinger-Westphal nuclei-->para. pregang. fiber to ciliary ganglia-->para. postgang. fiber to constrictor pupillae
-The fact that it goes to the other side is important because it will give a **consensual light reflex as well as the *direct light reflex |
|
|
Term
| What is the accommodation-convergence reflex? |
|
Definition
-From switching from far to close vision
-Has three parts; accommodation, convergence, and pupillary constriction |
|
|
Term
| What are Argyll Robertson pupils? When do we see it? |
|
Definition
-When we get accommodation-convergence reaction, but both direct and consensual light reflexes are lost
-Essentially, impaired response to light
-See it often in **neurosyphilis
-Can also see in MS, pineal tumors, & tabes dorsalis |
|
|
Term
| How many neurons are in the visual pathway? |
|
Definition
| -Three; starts with bipolar cell, then the ganglion cell, then synapses at the LGN and runs to the visual cortex |
|
|
Term
| Where is the fovea? What is in it? |
|
Definition
-It is lateral to the optic disk and contains only cones
-It is where we focus an image |
|
|
Term
| What is in the posterior and anterior chamber? |
|
Definition
| -Post. is vitreous, ant. is aqueous |
|
|
Term
What are the receptors for;
-Pupillary sphincter
-Radial dilator
-Ciliary muscle
-Ciliary epithelium |
|
Definition
-Pupillary sphincter; M3 (PANS)
-Radial dilator; a (SANS)
-Ciliary muscle; M3 (PANS)
-Ciliary epithelium; B (SANS)
-The last secretes aqueous humor and is the reason B blockers can be used to treat glaucoma |
|
|
Term
| What is a Marcus Gunn pupil? How do we find it? |
|
Definition
-Loss of afferent because of optic nerve lesion on one side
-A consensual light reflex, but not direct is present
-Test this with a swinging flashlight test where we shine in the contralateral eye, which produces constriction, but then we swing to the affected eye, which will produce paradoxical bilateral dilation
-Can occur in MS |
|
|
Term
|
Definition
-It is basically the same as Argyll Robertson pupils, but now we get sluggish reaction to light
-From ciliary ganglion lesion
-More in women
-Associated also with suppressed knee jerks |
|
|
Term
| What will uncal herniation produce? |
|
Definition
-AKA transtentoral herniation (most med. part of it)
-Compresses CN III and produces down and out syndrome
-Also get the dilated pupil (first symptom) and ptosis |
|
|
Term
| What is in the outer and inner nuclear layer? |
|
Definition
-The outer is of the rods and cones
-The inner is of the bipolar cells |
|
|
Term
| What do we have to worry about for occlusion of the middle cerebral and posterior cerebral arteries? |
|
Definition
-Middle serves the temporal, so the Meyer loop will be effected (producing contralateral superior quadrant loss in both eyes)
-The post. cerebral serves the visual cortex and the medial optic radiation (contra lower, and contra hemi) |
|
|
Term
| What is the most obvious difference in symptoms between lesions in front and behind the optic chiasm? |
|
Definition
-In front of gives monocular symptoms, behind give binocular
-Also, behind always gives contralateral visual field deficits |
|
|
Term
| What will be the difference between visual symptoms produced by a pituitary adenoma and a craniopharyngioma? |
|
Definition
-Both will give bitemporal symptoms; only lesion point that will give heterogenous symptoms
-The *adenoma is pressing from below, and the craniopharyngioma is from above
-This means with the adenoma we will get superior deficits, and with the craniopharygioma we will get inferior deficits (similar to ACA aneurism) |
|
|
Term
| How would you tell the difference between an optic radiation lesion and an optic tract lesion? |
|
Definition
-The optic tract still has the reflex afferents in them
-Will give a reduced pupillary reflex, along with the homonymous hemianopsia |
|
|
