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53 Cards in this Set
- Front
- Back
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Projections from which retinal photoreceptors will cross at the optic chiasm?
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Those on the nasal side of the fovea centralis
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T/F The macula lutea is medial to the optic disc
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False
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Name the course of projections from the retinal photoreceptors in the conscious image forming pathway
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Retinal photoreceptor>
Optic nerve> Optic chiasm> Optic tract> LGN> Optic radiation> V1 |
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What type of information is represented in one layer of the LGN?
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Magno or parvocellular information from half a retina from one eye
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Where is V1 located?
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Banks of the calcarine sulcus
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What are the functions and projections of the:
Suprachiasmatic nucleus Superior colliculus Pretectum Pulvinar |
SCh - projects to hypothal, on to pineal gland. Time keeper & melanin.
SC - attention and avoidance Pretectum - projects to Edinger-Westphal - pupillary reflex Pulvinar - projects to V2-V5 - attention and integration |
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Which quadrant of visual field does the Meyer's loop contain?
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Upper contralateral quadrant
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Describe the process of visual signal transduction, from light hitting a rod or cone to a neural signal
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Light hits photoreceptor>
Conform change and G protein cascade> Reduction in cGMP> Closure of Na and Ca channels> K channels remain open> Hyperpolarisation> Reduction in glutamate release |
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What type of cell connects rods and cones to ganglion cells?
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Bipolar cells
"Off" or "On" cell type determined by response to glutamate. "On Bipolar Cells" depol in response to glutamate, increasing activity in ganglion by inverting the hyperpolarised signal |
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How are single points of the retina processed for different types of info (e.g. colour, shape, movement etc)?
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Parallel Processing
Every point of retina is covered by every type of ganglion cell |
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T/F peripheral vision is totally spared in macular degeneration
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True
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What is the ventral stream of the visual cortex concerned with processing? What would a lesion cause?
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WHAT an object is
Difficulty with object processing |
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What is the dorsal stream of the visual association cortex concerned with processing? What would a lesion cause?
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WHERE and object is and how it is moving
Causes problems detecting motion and grasping objects |
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T/F Cones in the retina connect to only one ganglion
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SOMETIMES!!!
Cones in the central retina connect to only one ganglion, whilst cones in the periphery connect to many |
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Damage to the temporal lobe is most likely to effect which part of the visual field?
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The contralateral upper quadrant (in both eyes)
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T/F Sympathetic activation causes pupil constriction mediated by sphincter pupillae
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False
PARAsympathetic activation causes the following |
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T/F Sympathetic activation causes pupil dilation mediated by dilator pupillae
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True
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What would the pupillary reflex be in someone with Relevant Afferent Pupillary Defect (RAPD)? What structure is most commonly affected?
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Normal consensual response of effected eye, reduced direct response.
Optic nerve. |
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Describe the facial symptoms and underlying pathology of Horner's Syndrome
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Unilateral
Partial Ptosis (loss of symp innervation of superior tarsal muscle) Miosis (pupil constriction because of loss of symp inhib of sphincter pupillae) Anhidrosis (reduced symp causes reduced sweating) |
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Which artery supplies the inner retina?
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Central retinal artery (branch of opthalmic artery)
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Which artery supplies the optic nerve?
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Posterior ciliary artery (branch of opthalmic artery)
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Giant cell arteritis of which artery is most likely to result in a pale retina and pale optic nerve? What other finding is commonly associated with these signs?
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Opthalmic artery
Prominent temporal artery |
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What is the predominant type of ganglion cell in the cochlea?
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Type I (95%): large cell body, myelinated,
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What is the primary factor determining whether hearing will be regained following a cochlear implant?
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Age - must be young enough for neural plasticity
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Describe the pathway of cochlear action potentials to the auditory cortex
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Cochlea>
auditory n.> cochlear nucleus (open medulla)> superior olive (pons)> inferior colliculus (caudal midbrain)> medial geniculate body (thal.)> auditory cortex |
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T/F Hearing sensed in one ear is processed bilaterally in the auditory cortex
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True - the signal is split bilaterally from the cochlear nucleus
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Which cell type forms myelin in the CNS?
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oligodendrocyte
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T/F Relapsing remitting is the major course/form of MS, representing around 60% of MS
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False - ~80%
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Name 5 signs associated with multiple sclerosis
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optic neuritis
diplopia paraesthesia dysarthria and dysphagia limb weakness ataxia neurogenic bladder Uthoff's phenomenon (worse in heat) Lhermitte's sign ('electric shock' on neck flexion) |
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What investigations should be done for a suspected case of multiple sclerosis?
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Contrast MRI (lesions in GM)
Lumbar puncture for immunoglobulins |
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T/F axons are spared from destruction due to demyelination in MS
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False - although axonal loss is relatively much less significant than myelin
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What is the cause of multiple sclerosis?
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Probably a combination of genetic factors (30% concordance in MZT - MHCII?) and environmental (EBV??)
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T/F prevalence of MS increases nearer the equator
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False
The opposite is true, possibly due to protective nature of Vitamin D |
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What is the mechanism of multiple sclerosis?
(n.b. AI mech is probable but evidence exists against) |
Environ + genetics>
Activated CD4+ in periphery> TH1 (>macrophage) TH2 (>Ab) CD8+ TH17 (leukocyte recruit) >> myelin damage |
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How do T-cells penetrate the BBB in MS?
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alpha-4 integrin binds endothelium
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What therapies are used for multiple sclerosis?
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Restore BBB with:
corticosteroids alpha-4 integrin antag (natulizimab) Reduce inflammation: interferron b (T cell prolif, MHCII, TNF prod) plasmapheresis |
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What is the most common cause of neurologic disability in young adults?
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Multiple sclerosis
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What are typical signs of multiple sclerosis at ONSET?
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weakness, diplopia, optic neuritis, unsteady gait, vertigo, sphincter disturbance
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Name five signs in ESTABLISHED multiple sclerosis?
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Motor: UMN weakness, spacticity, Uthoff's
Sensory: parasthesiae, numb, pain, Lhermitte's, trigeminal neuralgia Cerebellar: gait ataxia, intention tremor, dysarthria Opthal: optic neuritis, diplopia, polydirectional nystagmus Sphincter disturb: urge incontinence, frequency |
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T/F Th1 cells are probably more important than Th2 in the pathogenesis of multiple sclerosis
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True
Lymphocytes are often absent in early MS lesions |
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How is a diagnosis of multiple sclerosis made?
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1. Clinical signs and symptoms
2. Imaging: lesions in CC, periventricular, brainstem, cerebell, SC 3. CSF: protein elevation (in ~30%), increased IgG in oligoclonal bands (in ~75%) |
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Which correlates better with loss of function in multiple sclerosis: axonal loss or myelin loss?
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axonal loss
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List in order of smallest > largest (structure wrapped)
Endoneurium Epineurium Perineurium |
Endoneurium (surrounds axon)
Perineurium (envelopes fascicle) Epineurium (binds fascicles) |
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Name the process that describes the degeneration of a nerve distal to a cut/crush point
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Wallerian degeneration
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Define a motor unit
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A single motor neuron plus the fibres it innervates
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Describe the cross-sectional appearance of a group of muscle fibres that have lost an innervating axon
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Loss of chequerboard appearance. Previously multiple fibre types are replaced by a single fibre type of the neighbouring axon that reinnervates.
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Describe the pathophysiology and primary fibre type effected by beri beri
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Thiamine deficiency (B1) causes loss of small and distal fibres. Can be caused by alcoholism. Predominantly sensory rather than motor.
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Describe the peripheral neuropathy caused by pernicious anaemia
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B12 deficiency (stores last 10 years)
Demyelinating and axonal loss May be autoimmune |
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Describe the peripheral neuropathy caused by Charcot-Marie-Tooth
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An inherited, length-dependent dysmyelination causing foot-drop, clawed toe, high arched foot and lower leg wasting
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Describe the peripheral neuropathy caused by Guilla- Barre syndrome
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An acute inflammatory demyelinating (autoimmune) response to Schwann cells. Causes acute motor weakness/paralysis and hypo/areflexia. Often resolves spontaneously.
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What proportion of diabetics experience a related neuropathy?
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~30%
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Describe the character of neuronal loss in diabetic neuropathy
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Focal, peripheral and autonomic
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Describe the pathophysiology behind diabetic neuropathy and how to prevent it
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Neurons are obligate glucose users
High blood glucose> High neuronal sugar> Disrupted energy transfer in mitochondria, increased ROS, peroxidation of lipids and protein> Neuronal death + impaired glial metabolism and endoneurial ischaemia Prevention: tight control of blood sugar |
