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80 Cards in this Set
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- Back
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in smaller muscles, how many muscle fibers does an alpha motor neuron innervate?
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just a few - results in finer control of movement
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cerebellum influences motor activity on which side?
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ipsilateral - projects to contralateral motor cortex and red nuclei whose fibers cross back over
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what does the anterolateral system/spinothalamic tract carry?
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pain, temperature, crude touch, and pressure
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what information do the dorsal columns carry?
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fine touch, vibration, concious proprioception
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where does the corticospinal tract deccussate?
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as it descends through the inferior aspect of the medulla through the medullary pyramids
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where do the dorsal columns cross over?
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between their nuclei in the brainstem and the thalamus via the arcuate fibers of the medial lemniscus
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where do the axons of the spinothalamic tract cross over?
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almost immediately after their first-order synapes in the dorsal horn
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what are the neurological deficits that occur in Brown-Sequard syndrome?
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ipsilateral motor loss and loss of touch, vibration, propriceptive sense; contralateral pain and temperature loss
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where do the motor and sensory deficits manifes in patients with a lesion of the internal capsule?
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corticospinal tract, dorsal columns, and spinothalamic tract travel to or from the cerebral cortex through the posterior limb - contralateral hemiplegia and contralateral sensory loss
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what is the primary mode of analgesic relief of opiods?
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inhibition of the spinothalamic tract
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what disorder is characterized by loss of pyramidal cells in the cerebral motor cortex that leads to fibrosis of the lateral corticospinal tracts
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ALS
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what is usually spared in ALS?
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sensory tracts and cognitive function
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what are signs of UMN lesions?
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spastic paralysis, hyperactive deep tendon reflexes, and clonus - UMNs are tonically inhibitory to LMNs
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what are signs of LMN lesions?
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hporeflexia, fasciculations, flaccid paralysis
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familial forms of ALS have been associated with what?
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mutations in the zinc/copper superoxide dismutase gene, which plays an important role in scavenging free radicals in metabolically active cells such as neurons
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periventricular plaques on MRI and oligoclonal bands in CSF are indicative of what?
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MS
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what is destroyed in Parkinson's?
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dopaminergic neurons in the substantia nigra
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what kind of drug is bromocriptine?
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dopamine receptor agonist
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what is benztropine? why is it useful in PD?
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anticholinergic - relative excess of Ach because of dopamine deficiency; anticholinergics can be useful in treating motor symptoms
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what compound that may be found in ilicit drugs can cause PD?
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MPTP - selectively destroys neurons in the substantia nigra
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what is the difference between tremor in PD and tremor in cerebellar dysfunction?
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PD - resting tremor
cerebellar dysfunction - tremor associated with volitional movements |
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what is MG often associated with?
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thymoma
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what is the pathophysiology of motor weakness in MG?
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antibodies to the post-synaptic nicotinic ACh receptors on skeletal muscle fibers
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what type of receptors are nicotinic receptors?
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ligand-gated sodium channels
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what kind of drug is edrophonium?
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short-acting cholinesterase inhibitor - increases concentration of ACh in synaptic cleft
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what are the long-acting cholinesterase inhibitors?
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pyridostigmine and neostigmine
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what are the side effects of cholinesterase inhibitors?
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excessive PNS stimulation - diarrhea, miosis, bronchospasm, excessive urination, bradycardia, salivation, lacrimation; also sweating because SNS stimulates sweating via ACh
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how do you treat organophosphate poisoning?
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treatment aimed at reducing total cholinergic activity - palidoxine regenerates active cholinesterase, and anticholinergic atropine
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what is Lambert-Eaton syndrome?
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AI disease with antibodies to voltage-gated calcium channels located in terminal bouton of presynaptic neurons result in impaired ACh release
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what is Lambert-Eaton syndrome often associated with?
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paraneoplastic syndromes, particularly small cell CA of lung
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bilateral loss of pain and temperature sensation?
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syringomyelia
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what is syringomyelia?
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expanded fluid-filled cavity in spinal cord that affects the spinothalamic tract
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what produces atrophy of the muscles of hands and hypoactive reflexes of the upper extremities in syringomyelia?
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expansion of the syrinx to compress the ventral horns - produces LMN signs
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what should you examine for masses in a patient with trigeminal neuralgia?
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posterior fossa
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what drug is used to treat trigeminal neuralgia?
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carbamazapine - reduces rate of nerve transmission by inhibiting voltage-gated sodium channels of neurons
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what are CSF findings in MS?
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oligoclonal immunoglobulin bands (absent in serum), elevated IgG, and myelin basic protein
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this is a disease that involves demyelination of various white matter areas of the CNS
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MS
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what cell type is attacked and destroyed during an exacerbation of MS?
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oligodendrocytes
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this syndrome is due to demyelination of peripheral nerves
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Guillan-Barre
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this type of stroke primarily results from atherosclerosis and subsequent thrombus/embolism or from hypercoaguability in LA (e.g. atrial fibrillation) or LV (after MI)
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ischemic stroke
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this type of stroke results predominantly from trauma, ruptured AV malformation, ruptured aneurysm, or vessel rupture due to hypertension
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hemorrhagic
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how does atrial fibrillation predispose to stroke?
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makes it easier for blood to pool and clot within the atria, and the clots can then embolize to brain
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what serves the motor and sensory cortex devoted to the contralateral leg?
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anterior cerebral artery
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what does the MCA supply?
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motor and sensory cortex for contralateral upper extremity, head, neck, and face
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what artery supplies Broca's and Wernicke's areas?
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MCA (typically on left)
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occlusion of what can cause left homonymous hemianopsia?
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right posterior cerebral artery - supplies visual cortex in occipital lobe
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worst headache of life, N&V, stiff neck, photophobia?
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subarachnoid hemorrhage
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where do you do an LP?
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L3-L4 or L4-L5 (SC terminates at L1-L2)
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what are the common causes of subarachnoid hemorrhage?
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ruptured berry aneurysm, ruptured AVM, head trauma (most common)
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patients with PKD most often have berry aneurysms in what location?
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bifurcation of anterior communicating artery
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almost one-half of cases of this are idiopathic; the rest develop after meningitis, subarachnoid hemorrhage, or intracranial surgery or develop as a result of a tumor
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hydrocephalus
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CSF flows from the lateral ventricles into the third ventricle via what?
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foramen of Monroe
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CSF flows from the third ventricle to the fourth ventricle via what?
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cerebral aqueduct (aqueduct of Sylvius)
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how is CSF reabsorbed?
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empties into dural venous sinuses via arachnoid granulations
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trauma that causes unconsciousness followed by lucid interval followed by confusion, lethargy, disorientation
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epidural hematoma - intracranial bleeding that dissects periosteal dura away from skull
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this is composed of a periosteal layer adherent to bone and a meningeal layer continuous with the arachnoid layer
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dura mater
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what artery is most commonly involved in an epidural hematoma?
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middle meningeal artery - ruptures between dura and skull
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this layer attaches directly to brain parenchyma
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pia
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does CSF show RBCs in an epidural bleed?
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no - blood does not reach subarachnoid space where CSF is located
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what structures are typically involved in a subdural hematoma?
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bridging veins that interconnect the subarachnoid space and the dural (venous) sinuses - more common in elderly people whose brains have atrophied
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what carries the efferent part of the corneal reflex?
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facial nerve - causes contraction of the orbicularis oculi
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what carries the afferent part of the corneal reflex?
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V1
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anticonvulsant with gingival hyperplasia, nystagmus, and ataxia as side effects?
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phenytoin
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anticonvulsant with hepatotoxicity as potential side effect?
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valproic acid
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anticonvulsants that can cause Stevens-Johnson syndrome?
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lamotrigine, ethosuximide
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anticonvulsants that can cause respiratory depression?
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phenobarbital, diazepam
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anticonvulsant that can cause agranulocytosis?
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carbamazepine
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anticonvulsant that can cause tremor?
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gabapentin
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what is the first line treatment for absence seizures?
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ethosuximide
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what effects do most anticonvulsants have on neuronal discharge?
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decrease the frequency of neuronal discharge by increasing the threshold for neuronal discharge - most do so by blocking sodium or calcium channels, but benzos activate chloride channels to hyperpolarize neurons
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how are AD and Pick's disease different?
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AD: diffuse cerebral atrophy
Pick's: selecive atrophy of frontal and temporal lobes |
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what class of drug is used to treat AD?
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cholinesterase inhibitors - AD is associated with selective destruction of cholinergic neurons
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if a patient with AD has depression, what drugs should not be prescribed?
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TCAs because they have powerful anticholinergic side effects that may exacerbate the cognitive decline due to AD
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what is the mechanism whereby short-term memory is consolidated into long-term memory?
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long-term potentiation - occurs in hippocamus
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what is the second most common cause of dementia in the elderly?
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multi-infarct dementia - focal neurologic defects
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what is the most common primary brain tumor?
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astrocytoma
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what is the worst grade of astrocytoma?
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glioblastoma multiforme
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what type of tumor has a characteristic pseudopaliasding arrangement of tumor cells?
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glioblastoma multiforme
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why are lomustine and carmustine more suitable for treating brain tumors?
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belong to a class of alkylating agents - nitrosureas - can effectively penetrate the BBB
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what is a meningioma?
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benign tumor that arises from the arachnoid cells of the meninges - external to brain and so usually can be surgically resected
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