Neuro Flashcards
<p>Describe the neurologic visual pathway anterior to posterior </p>
<p>Optic nerve → chiasm → optic tract → lateral geniculate body → optic radiation → occipital lobe</p>
<p>How many nerve fibers are found in an adult optic nerve?</p>
<p>composed of 1.2 million nerve fibers</p>
<p>What is the average diameter of the optic nerve?</p>
<p>approximately 1.5 mm in diameter</p>
<p>What is the diameter of the optic nerve at the lamina cribrosa? Why is it larger?</p>
<p>enlarges to 3.5 mm posterior to lamina cribrosa due to myelin sheath</p>
<p>How far is the optic nerve from the fovea (approximately)?</p>
<p>located 3–4 mm from fovea</p>
<p>Where is the physiologic blind spot (due to the optic nerve) located?</p>
<p>absolute scotoma is15° temporal to fixation and slightly below horizontal meridian</p>
<p>What is the total length of the optic nerve?</p>
<p>approximately 45-50 mm in length</p>
<p>What is the intraocular length of the optic nerve?</p>
<p>1mm</p>
<p>What is the intraorbital length of the optic nerve?</p>
<p>25mm</p>
<p>What is the intracanalicular length of the optic nerve?</p>
<p>9mm</p>
<p>What is the intracranial length of the optic nerve?</p>
<p>10-15mm</p>
<p>At which location does the optic nerve begin to aquire myelin?</p>
<p>psoterior to the lamina cribrosa</p>
<p>Which layer of the meninges merges with the sclera?</p>
<p>dura mater - outer layer</p>
<p>Which layer of meninges is fused to the surface of the nerve?</p>
<p>pia mater- inner layer</p>
<p>Between which two layers of meninges is the space that contains CSF?</p>
<p>space between arachnoid and pia contains cerebrospinal fluid (CSF)</p>
<p>Through which structure does the optic nerve run before entering the optic canal?</p>
<p>annulus of Zinn (ring of tendinous origins of the rectus muscles)</p>
<p>What are the dimensions of the optic canal?</p>
<p>9 mm long and 5–7 mm wide</p>
<p>Which wall of theoptic cannal isthinnest?</p>
<p>medially, adjacent to ethmoid and sphenoid sinuses</p>
<p>Where does the dura of the optic canal fuse in the optic canal?</p>
<p>dura of ON fuses with PERIOSTEUM of canal</p>
<p>Where doesthe interal carotid artery emerge from the cavernous sinus?</p>
<p>laterally</p>
<p>What artery supplies the orbital portion of the optic nerve?</p>
<p>ophthalmic artery with meningeal anastomoses</p>
<p>Which blood vessels supplythe INTRACANALICULARportion of the optic nerve?</p>
<p>pial branches from ophthalmic artery</p>
<p>possibly internal carotid artery (ICA)</p>
<p>Which blood vessels supply the INTRACRANIAL portion of the optic nerve?</p>
<ul> <li>small vessels from ICA</li> <li>anterior cerebral and anterior communicating arteries</li></ul>
<p>Where is the optic chiasm located?</p>
<p>10 mm above pituitary gland</p>
<p>What percentage of optic nerve fibers decussate at the chiasm?</p>
<p>55% of ON fibers cross in chiasm</p>
<p>Which retinal fibers decussate at thechiasm (nasal or temporal)?</p>
<p>nasal retinal fibers cross in chiasm to contralateral optic tract (decussating nasal fibers); temporal fibers remain uncrossed; macular fibers run posteriorly (posterior compression leads to bitemporal defect)</p>
<p>Which retinal fibers course through Willebrand's knee? What type of scotoma is produced?</p>
<ul> <li>inferonasal retinal fibers cross in chiasm and course anteriorly approximately 4 mm into contralateral ON before running posteriorly</li> <li>produces junctional scotoma</li></ul>
<p>where are the carotid arteries located relative to the chiasm?</p>
<p>Carotid arteries course on either side of chiasm</p>
<p>What is the main blood supply to the chiasm?</p>
<p>ICA; occasionally by anterior cerebral and anterior communicating arteries</p>
<p>Where are teh lower retinal fibers found in the optic tract?</p>
<p>lower fibers lie laterally (90° rotation of fibers)</p>
<p>around which structure does the optic tract course?</p>
<p>tract courses laterally around cerebral peduncle</p>
<p>Why does damage to the optic tract result in a contralateralrAPD?</p>
<p>Damage to optic tract results in contralateral relative afferent pupillary defect (RAPD) because 55% of fibers cross (greater quantity of nasal fibers [nasal to fovea]), including the large monocular crescent (which corresponds with the extreme nasal retina)</p>
<p>How does vision contribute to control of diurnal rhythms?</p>
<p>Special fibers run to the hypothalamus, contributing to neuroendocrine systems that control diurnal rhythms</p>
<p>What type of reflexes is the superior colliculus involved in?</p>
<p>involved in foveation reflexes (receives input from pupillary fibers); injury disrupts eye movements but does not cause visual field (VF) defect</p>
<p>What is the blood supply of the optic tract?</p>
<ul> <li>anterior choroidal artery</li> <li>branches from posterior communicating artery</li></ul>
<p>the Lateral geniculate bodyis a part of which neuroanatomical structure?</p>
<p>part of the thalamus</p>
<p>To which layers in the LGB do crossed fibers project?</p>
<p>Crossed fibers(contralateral eye): project to layers 1, 4, and 6</p>
<p>Towhich layers in the LGB do uncrossed fibers project?</p>
<p>Uncrossed fibers(ipsilateral eye): project to layers 2, 3, and 5</p>
<p>In which layers of the LGB are magnocellular (M-cell) neurons found?</p>
<p>layers 1 and 2</p>
<p>What visual role do Magnocellular (M) cells play?</p>
<ul> <li>motion detection</li> <li>stereoacuity</li> <li>contrast sensitivity</li></ul>
<p>To wich layer of the visual cortex do M cells project?</p>
<p>project to layer 4C alpha of visual cortex</p>
<p>In which layers of the LGB are Parvocellular neurons (P cell) found?</p>
<p>layers 3 to 6</p>
<p>What visual role do Parvocellular (P) cells play?</p>
<ul> <li>fine spatial resolution</li> <li>color vision</li></ul>
<p>To which layer of the visual cortex do P cellsproject?</p>
<p>layer 4C beta of visual cortex</p>
<p>In which areas of the LGB do the Koniocellular neurons (k cells) reside?</p>
<p>sit in interlaminar zones and superficial layers</p>
<p>From which 2 structures do K cells receive input?</p>
<p>receive input from both retinas and the superior colliculus</p>
<p>What is the blood supply to the LGB?</p>
<p>anterior communicating artery and choroidal arteries</p>
<p>What structure in the visual pathway connects the LGB to the occipital cortex?</p>
<p>optic radiations</p>
<p>How do superior retinal fibers travel through the optic radiations?</p>
<p>Superior retinal fibers(inferior VF)travel in white matter underneath parietal cortex to occipital lobe</p>
<p>How doe the inferior retinal fibers travel through the optic radiations?</p>
<p>Inferior retinal fibers(superior VF)travel around ventricular system into temporal lobe (Meyer’s loop)</p>
<p>Where is Meyer's loop located relative to the temporal lobe?</p>
<p>Meyer’s loop is about 5 cm from tip of temporal lobe</p>
<p>What visual field defect can be seen with an injury to Meyer's loop?</p>
<p>temporal lobe injury causes incongruous homonymous superior quadrantanopia, or a ‘pie-in-the-sky’ VF defect</p>
<p>Where do the macular fibers travel through the optic radiations relative to the retinal fibers?</p>
<p>travel more centrally than do inferior retinal fibers</p>
<p>What is the blood supply to the optic radiations?</p>
<p>middle cerebral arteries</p>
<p>Where is the primary visual cortex located?</p>
<p>medial face of occipital lobe</p>
<p>Which structure divides the primary visual cortex?</p>
<p>divided horizontally by calcarine fissure</p>
<p>Does the visual cortex contain infromation from the contralateral or ipsilateral eye?</p>
<p>Visual cortex contains a topographic map of the contralateral hemifield</p>
<p>Where is the macular region foudn in theprimary visual cortex?</p>
<p>Macular region is posterior, extending slightly onto lateral aspect of occipital lobe</p>
<p>Where is th eperipheral visual field located in the visual cortex?</p>
<p>Peripheral VF is located anteriorly along calcarine fissure</p>
<p>Which is the only site posterior to the chiasm that if injured would cause a monocular VF defect?</p>
<p>Temporal crescent</p>
<ul> <li>each VF (from 55° to 100°) is seen only by nasal retina of ipsilateral eye; located most anteriorly</li> <li>may also be the only portion of VF spared after occipital lobe damage</li></ul>
<p>What is the blood supply to the primary visual cortex?</p>
<p>middle and posterior cerebral arteries</p>
<p>Where do the sympathetic fibers from the hypothalmus synapse? Where is this located?</p>
<p>CILIOSPINAL CENTER OF BUDGE</p>
<p>located at level C8–T2</p>
<p>Where do the 2nd order sympathetic fibers synapse?</p>
<p>SUPERIOR CERVICAL GANGLIA</p>
<p>Is the ciliary ganglia sympathetic or parasympathetic?</p>
<p>parasympathetic</p>
<p>Where is the ciliary ganglia located?</p>
<p>1 cm from optic foramen between ON and lateral rectus muscle</p>
<p>Name the 3 nerve fiber roots that are received by the ciliary ganglion:</p>
<p>Which ones synapse?</p>
<ol> <li>Long sensory</li> <li>Short parasympathetic (synapse)</li> <li>Sympathetic (do not synapse)</li></ol>
<p>What is the role of the long sensory nerves?</p>
<p>sensory from:</p>
<ul> <li>cornea</li> <li>iris</li> <li>ciliary body</li></ul>
<p>What is the role of the short parasympathetic fibers of the ciliary ganglion?</p>
<p>motor to ciliary body and iris sphincter</p>
<p>What is the role of the sympathetic fibers of the ciliary ganglion?</p>
<p>conjunctival vasoconstrictor fibers and iris dilator</p>