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11 Cards in this Set
- Front
- Back
Afferent pathway of the pupil reflex
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Optic: Axons may arise in optic tract or above it, but pass without synapsing in LGN and synapse directly in pretectal area of brainstem.
Brainstem: Neurons from pretectal project to ipsilateral E-W nucleus AND via post commissure to contra pretectal and E-W nucleus (Direct and consensual response) |
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Efferent pathway of the pupil reflex
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Parasym from E-W to ciliary ganglion where they synapse, ultimately innervating pupillary sphincter (miosis)
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What kind of receptors are in the synapses of pupil reflex?
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Muscarinic
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Major responsibilities of CN III
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Carry pupillary reflex neurons, raise eyelid, extraocular eye movement (MR, IR, SR, IO)
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Pupil symptoms in R CN III damage (efferent), for example
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1. R pupil dilated at rest
2. R will not show consensual response 3. R will not show direct response (while L will be consensual) 4. Mild outward deviation 5. Ptosis |
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Pupil symptoms in R retinal/optic damage (afferent), for example
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1. Normal at rest
2. R consensual intact 3. R direct will have no response and no L consensual response |
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Accomodation-Convergence reflex
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Convergence is mediated by CN III (medial rectus), while accomodation is increased sphericity and pupillary constriction parasym mediated by E-W nucleus
--Essentially all visual pathways must be intact |
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Pupillary dilation (sympathetic) pathway
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Hypothalamus -> lateral brainstem (congruent with ALS) -> T1-T2 -> SYNAPSE in lateral horn -> ascend to superior ganglion -> carotid plexus -> pupillary dilator muscle/superior tarsal (involuntary opening of the eyes)
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Horner's Syndrome. Symptoms?
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Interruption of sympathetic facial innervation.
Ptosis, miosis, anhydrosis |
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What happens to pupil when CN III is damaged?
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The sympathetic innervation wins, resulting in constant dilation of ipsilateral eye
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What happens in damage to the accomodation-covergence reflex (neuro degeneration)
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Light pupillary response is lost, but accomodation is usually intact? (31-28)
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