Chapter 21 Neurotransmitters and Pathways


23. C. Lambert-Eaton myasthenic syndrome is an autoimmune syndrome caused by a presynaptic defect of ACh release. It results in weakness in limb muscles, and muscle strength improves with use. It is associated with neoplasms (eg, lung, breast, prostate) in 50% of cases. 24. B. Huntington disease is a hereditary disorder that results from a loss of ACh- and GABA-containing neurons in the striatum. Some symptoms include jerky, random, uncontrol lable, rapid (choreiform) movements; slowness of saccadic eye movements; and progressive dementia. 25. A. The basal nucleus of Meynert produces acetylcholine, low levels of which are associated with Alzheimer disease. Dopamine is produced in the substantia nigra and ventral tegmental areas of the brain. Glutamate is produced through a recycling process involving the glial cells of the brain. Norepinephrine is primarily produced by the locus ceruleus in the brain. In the brain, serotonin is produced in the raphe nuclei; however, most serotonin in the body is produced in the gut. 26. C. Low norepinephrine would explain the lethargy and blood pressure/dizziness in this patient. A sclerotic plaque affecting the locus ceruleus would cause depressed levels of norepinephrine. The basal nucleus of Meynert produces acetylcholine, and the lack of acetylcholine would not produce the symptoms seen in this patient. The globus pallidus does contain high concentra tions of enkephalin, but that is mostly involved with pain suppression. The raphe nuclei are serotonin producers and are also involved with pain suppression. The substantia nigra produces dopamine, the lack of which produces movement symptoms, such as Parkinson disease. 27. D. Glutamate is the major excitatory neurotransmitter; 60% of brain synapses are glutamatergic. 28. A. GABA is the major inhibitory neurotransmitter and can be localized by using glutamic acid decarboxylase as a marker.

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