Term
Oculomotor system motorneuron firing during movement
-Tonicity changes
-Phase changes |
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Definition
*Tonic change in firing rate proportional to deviation of the eye in the direction of the action of the muscle--> maintain position
*Phasic change in firing rate proportional to velocity of movement the eye in the direction of the action of the muscle-->initiate movement |
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Term
Horizontal Saccadic Eye Movement
-Phase component
-Tonic component
-Pathway involving these two in horizontal gaze |
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Definition
*Phase component is achieved by a PULSE in firing rate. Without it the saccades are very slow and the eye is slow to reach its new target
*Tonic component achieved by a subsequent STEP firing rate. Without it the eye will rapidly move to the new target then snap back to a straight ahead position
*Pathway to move one eye: Ipsilateral F. Eye Fields or Sup. Col.--> PPRF (Pulse)-->Integrator (Step)--->Both to CN IV nucleus-->lateral rectus-->proper saccade |
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Term
-Saccadic Horizontal Conjugate Eye Movement Pathway
-VOR Horizontal Conjugate Eye Movement Pathway |
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Definition
Saccadic [essentially half the VOR] *Ipsilateral (PPRF/Integrator) --> Nuc. IV-->--> dual outputl *1) Nuc IV--> ipsilateral CN IV--> ipsilateral lateral rectus *2) Nuc IV--> contralateral MLF--> Nuc III--> CN III--> contralateral medial rectus
VOR
*Head rotation to the right-->inc. Firing in right (ipsilateral) semicircular canal--> right (ipsilateral) vestibular nuceli--> dual output
*1) -->left (contralateral) MLF-->Excite left (contralateral) Nuc IV--> excite the left (contralateral) CEM pathway
*2) -->right (ipsilateral) MLF--> Inhibit right (ipsilateral Nuc IV--> inhibit the right (ipsilateral) CEM pathway
*Both eyes are thus rotated to the left (contralateral) |
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Term
| Spontaneous/Vestibular Nystagmus |
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Definition
*Loss of function in labrynth or CN VIII on one side
*Contralateral continues to fire as normal
*The lack of signal from canal on one side is interpreted as continuous acceleration towards the the contralateral side
*This drives a continuous VOR
*The fast phase is AWAY(contralateral) from the lesion???? |
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Term
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Definition
Diagnostic test of canal function and ocular reflexes
*Production of convection currents to deflect cupula and trigger VOR
*ColdOppositeWarmSame: COWS
*Cold water in one ear produces a contralateral(fast phase) nystagmus
*Warm water in one ear produces an ipsilateral (fast phase) nystagmus |
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Term
Galetta
Key to localizing lesions to the medial and lateral Pons |
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Definition
Medial Pons
*MLF
*CN VI (PPRF?) and VII
*CST (decussated)
*Medial Leminiscus (decussated)
Lateral Pons
*CN V and VIII
*ALS (decussated)
*MCP |
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Term
Galetta
Localization lesions to Medial or Lateral Medulla |
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Definition
Medial Medulla
*CN XII/nucleus
*ML (DCML, decussated)
*Pyramids (CST, decussated)
Olive?
Lateral Medulla
*CN IX/nucleus
*CN X/nucleus
*STT/ALS (decussated) |
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Term
Galetta's Rules for
Localization of Brainstem Lesion
2. Transverse localization by effect on
-Medial or Lateral notable CN nuclei
-Motor vs sensory tracts
3. Localization of Xed hemiparesis by CN's often associated with it |
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Definition
2. Transverse local
*Medial: III, IV, VI, XII
?VII?
*Lateral: V, VIII, X
-Motor and Sensory Tracts
*Motor tract: Anteriomedial
*Sensory tracts: dorsal and lateral
3. Xed Hemiparesis oft associated CN
*III (Midbrain)
*VI (Caudal Pons)
*VII (Caudal Pons)
*XII (Medulla) |
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Term
************************
Swinging Flashlight Test
-CN tested
-Interpretation of dysfunction |
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Definition
Nerve Tested
*Afferent: CN II Optic Tract/Chiasm/
Dysfunction
*Unilateral defect/Marcus Ginn
-Light in affected eye--> neither constrict
-Light in normal-->both constrict
-Swing light back to affected--> affected pupil paradoxically dilates
*Afferent pupillary test will be normal in cataracts, FVL, and retinal damage
*Neither eye will constrict if their is true complete blindness |
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Term
************************
Corneal Reflex
-CN tested
-B.S. level tested (CN nuclei)
-Interpretation of dysfunction |
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Definition
| Ipsilateral CN V(S) and VII |
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Term
Galetta
Horner's Syndrome
*General features and etiology
*2 Confirmator Eye drop tests
*???Post or Pre Ganglionic Test |
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Definition
*Defect in sympathetic innervation
1)Sympathetic defect Miosis
2)Very mild ptosis
3)Anhidrosis
NO VISUAL SYMPTOMS
*Confirmation
1)Cocaine as a NRI to 3rd order neuron will dilate normal pupil but not the miotic one with sympathetic dysfunction
2) Apraclonidine is a weak agonist that won't dilate normal eye but might dilate the affected eye b/c of denervation supersensitivity |
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Term
************************
Lateral Medullary/Wallenburg Syndrome
-Etiology
-B.S. areas affected and resulting symptoms |
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Definition
Etiology
*Occlusion of PICA (possible vertebral?) |
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Term
Basic Ocular Anatomy
-3 Layers of the globe
-Internally, Three Chambers and the "---" |
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Definition
3 Layers of the Globe
1. Cornea and Sclera
2. Uveal Tract (Iris, cil. body, choroid)
3. Retina
Internal: 3 chambers and the lens
1. Anterior Chamber
2. Posterior Chamber
3. Vitreous |
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Term
Ocular embryological tissue origins
-1st Cell Line
-2nd Cell Line: important structure |
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Definition
Mesoderm
*Extraocular muscles
Ectoderm
*Neuroectoderm
*Neural Crest
*Surface Ectoderm: LENS! |
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Term
| Pathway of light/signal through the eye to the cortex |
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Definition
1. Cornea
2. Aqueous Humor
3. Lens
4. Vitreous Humor
5. Retina
6. Ganglion cells
7. LGN, Visual Cortex |
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Term
Refractive Errors in vision
-Myopia
-Hyperopia
-Astigmatism |
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Definition
Myopia: Nearsighted
Hyperopia: Farsighted
Astigmatism: Rays are refracted to different planes |
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Term
Cornea Structure and Function
-Stroma (Layer 3/5)
-Endothelium (layer 5/5 |
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Definition
-Stroma refracts 70% of light. Transparent due to avascularity, uniform collagen structure, and deturgescence.
-Endothelium pumps bicarbonate to maintain stromal deturgescence. Cannot regenerate. Dysfunction/damage leads to corneal edema and stromal destruction. |
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Term
Uveal Tract
-Iris
-Ciliary Body
-Choroid |
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Definition
Iris
*regulates pupil size
*Sphincter: ?Parasympathetic?
*Dilator: ?Sympathetic?
Ciliary body
*Make aqueous humor to nourish cornea and 2/3 of lens
*
*Muscle fibers attached to Zonules of Zin involved in lens accomodation
Choroid
*highly vascular; nourish the lens |
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Term
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Definition
Function
*Refract 30% light, accomodation for near vision, absorb UV
Components
*Capsule, cortex, and nucleus
*Zonules of Zinn link ciliary body and lens |
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Term
-Cataracts
-Glaucoma
-Macular Degeneration |
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Definition
Cataracts: age related
*Opacification of the lens
*Trouble focusing: blurry vision
*Interfere w/ red response?
Glaucoma
*Damage to ganglion cells
*Affects peripheral vision first leading to tunnel vision
*Many causes, but can be caused by decreased aqueous humor drainage/ increased eye pressure
Macular Degeneration: Age
*Dysfunction of Photoreceptors and RPE
*leads to atrophy and neovascularization |
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Term
Galetta
Near Response
-Triad
-Innervation
-Light/Near Dissociations |
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Definition
Triad
1. Pupillary Constriction (PS to iris)
2. Accomodation (PS's to ciliary m)
3. Convergence of eyes (PS to ocular m)
*NEAR response input to EW nucleus is anatomically separate from LIGHT (CN II) input to EW--> A pupillary light/near dissociation in CN II dysfunction.
*94% of the parasympathetics in the eye are dedicated to the NEAR response and only 6% to the light response, thus the light response is much more sensitive to PS dysfunction |
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Term
Galetta
Sympathetic pathway to eye and face
-3 neuron Pathway from Hypothalamus
-2 Eye innervations
-1 facial innvervation |
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Definition
Hypothalamus--> ALS??--> 1st synapse at T1--> exit and loop over the lung--> 2nd synapse at superior cervical ganglion-->
To the Face (1)
* SCG facial arteries
To the eye (2)
*SCG--> ascend with internal carotid a.--> enter cavernous sinus--> follow V1 and become long ciliary nerve--> entor orbit --> synapse on iris dilator muscle
*Other sympathetics in the cavernous sinus join with CN III to innervate upper and lower eyelids. |
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Term
Pathologic Aniscoria
*Which eye is the abnormal one?
*Two pathologic causes
1) Worst in light/poor light response
2) Worst in dark/normal light response |
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Definition
1) Big pupil is the affected eye:
*Defect in Ipsilateral Parasympathetics of CN III/Short Ciliary Nerves
2) Small pupil is the affected eye
*Defect in Ipsilateral Sympathetics: (can be part of Horner's Syndrome) |
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Term
*Features and Most common Etiology of...
*1st Order Horner's Syndrome
*2nd Order Horner's Syndrome
*3rd Order Horner's Syndrome |
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Definition
Everything is IPSILATERAL (unilateral)
*1st Order:
-Ipsilateral anhidrosis of the body and face, often with Brain stem/spinal lesion symptoms;
-Usually ipsilateral lateral medullary infarct-->Wallenberg crossed numbness
*2nd Order:
-Ipsilateral anhidrosis of the face
-Lung/neck tumors or trauma->poss. brachial plexus signs
*3rd Order:
-Ipsilateral anhidrosis of nose and medial forehead, often with ipsilateral facial/headache pain
-Trauma-->?Carotid dissection or occlusion?? |
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Term
| Localization paradigm of a dilated pupil |
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Definition
1)Midbrain: Other motor/sensory deficits
2)Subarachnoid: CN III Palsy: check PComm!
3)Cavernous Sinus: CN III, IV, V, and VI palsies. Can often be pupillary sparing, although concurrent Horner's will cause pseudopupillary sparing, masking the dysfunction. |
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Term
Adies Pupil
Cause and symptoms |
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Definition
Ciliary Ganglion Lesion(Viral?)
-Disrupts P.S. to sphincter and accomodation
*Dilated pupil
*No light response
*Segmented Iris
*???Tonic near response (unlike pharmacologic block)???
*Supersensitive to very low doses of pilocarpine |
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Term
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Definition
Usually Post Syphilitic
A light-near dissociation from a lesion somewhere in the dorsal midbrain
1) Miotic pupils with no light response
2) Intact Near response
3) Irregular pupels
4) Poor dilation from dark or drugs |
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Term
Rods vs Cones
-pigment
-speed
-sensitivity |
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Definition
Rods
-1 pigment for dark/lightcontrast
-Slow. Sensitive to 1 photon
-Scotopic: low acuity/light
-Mainly rods outside the fovea
Cones
-3 RGB pigments for color
- Fast, but require many photons
-Photopic: high acuity/light
-Fovea is cone only |
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Term
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Definition
1. Photon absorbed by rhodopsin pigment
2. which activates transducin G protein
3. which activates phosphodiesterase
4. which hydrolyzes cGMP
5. which closes Na+ channel allowing membrane to hyperpolarize
6. thus the photoreceptor STOPS releasing glutamate |
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Term
Bipolar cells in the retina
-Two types
-Receptive Field
-Modulation
-Contrast Neural Image |
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Definition
Types
1. Ionotropic OFF cells hyperpolarize in light
2. Metabotropic ON cells depolarize in light
Receptive Field of BP's:
*center derived from rod/cone input
*large ring where light has opposite effect compared to the center
*Creates center-surround antagonism
Modulation
*Horizontal cells carry signals from distant rods/cones to ?enhance? the center surround
*Center surround RF of BC's subtracts the mean luminescence converting the NEURAL IMAGE from one of light intensity to one of CONTRAST |
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Term
Ganglion cells
(Midget AKA P-Cells here; cone input only) |
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Definition
Only retinal cells that produce AP SPIKES
*ON/OFF ganglion cells convert the graded ON/OFF bipolar signals into spike trains
*Firing rates are modulated to further enhance contrast |
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Term
LGN portion of Retinogeniculostriate Pathway
-Organization
-Information from which retinas/visual field contained?
-M and P cells
-Gating |
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Definition
*Retinopically organized
*Contains the neural image of the contralateral eye field with foveal magnification
*Input from Ipsilateral temporal retina and contralateral nasal remain in separate layers
*M and P cells in separate layers
*Extraretinal inputs modulate LGN's gating of retinal information to the cortex when awake/asleep |
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Term
| Striate portion of Retinogeniculostriate Pathway |
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Definition
*AKA V1 AKA Primary Visual Area
*Retinotopically organized
*LGN M and P axons terminate in IVC with Left and Right Eye inputs separate
*M (Motion) and P (Color and unprocessed orientation) are separate throughout V1
*Modular: Orientation, Ocular Dominance, Color
*Binocular cells (stereopsis) in layer IVb:
*Outputs to Superior Colliculus, Pontine Nuclei, LGN, and other cortical areas
*Long range lateral connections modify responses from the receptive field. |
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Term
V2 portion of extrastriate cortex
-Gross Location
-3 Stripes and target streams |
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Definition
*Surrounds the V1/striate cortex
"M Pathway"
Thin: color--ventral
Pale interstripe: orientation-->ventral
"P Pathway"
Thick: orientation, direction of motion, distance-->dorsal |
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Term
Dorsal Stream Segments after V2
MT, MST, PPA
-Inputs
-Output
-Result of lesion |
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Definition
MT
*Input: V2 thick stripe(P) and V1 4B (M)
*full map of contralateral hemifield
*Solves aperture problem
*Out: motion of objects/surfaces to MST
*Lesion: akinotopsia inability to perceive motion-->difficulty with traffic, filling cups...
MST
-Output: Optical flow: motion and distance patterns/contrast of entire optical field
PPA
*Spatial Vision; Vision for action
*Lesion: NEGLECT of contralateral visual hemifield |
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Term
Ventral Stream Segments after V2
Function and Lesion
-V4
-ITC |
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Definition
V4
*Input: Color and orientation from V2 thin and pale stripes
*Function: Color constancy and form
*Lesion: Achromatopsia: cannot see or concieve about color
ITC
*Object and face recognition, image understanding.
*Lesion: Agnosias
Cannot recognize or understand object, faces, images |
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Term
????Mesial Frontal Lobe Syndrome????
-Symptoms
-Etiology |
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Definition
Symptoms
-Akinetic Mutism
-Utilization Behavior
-Transcortical motor Aphasia
Etiology
-ACA aneurysm rupture
-Midline tumor |
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Term
Conciousness
-Two Components and anatomic location |
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Definition
Arousal:
*Eye opening and motor function
*Reticular Activating System
Awareness:
*Sensation, thought, emotion
*Cerebral Cortex |
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Term
Coma
-Arousal: Brain Stem Function
-Awareness: Cortex Function
-Sleep/Wake Pattern
-Motor Function
-Respiratory Patterns and localization |
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Definition
*Absent arousal, awareness, S/W and motor function.
Respiratory Patterns:
*Cheyne Stokes
-Cycle of 1)increase 2)decrease 3)apnea
-Indicates Bilateral hemispheric injury
*Central Neurogenic Hyperventilation
-Rapid breathing
-Indicates Midbrain lesion
*Apneustic
-Rapid breathing with PAUSES
-Lower pontine lesion |
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