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{{WBRQuestion | {{WBRQuestion | ||
|QuestionAuthor={{Rim}} | |QuestionAuthor={{Rim}} {{Alison}} | ||
|ExamType=USMLE Step 1 | |ExamType=USMLE Step 1 | ||
|MainCategory=Biochemistry | |MainCategory=Biochemistry | ||
| Line 20: | Line 20: | ||
|MainCategory=Biochemistry | |MainCategory=Biochemistry | ||
|SubCategory=Neurology | |SubCategory=Neurology | ||
|Prompt=A researcher | |Prompt=A researcher investigating the regulatory neurotransmitters in the basal ganglia sends high frequency electrical impulses into specific areas of the brain of a rat and measures the change in the local concentration of several neurotransmitters. Upon stimulation of the caudate, the researcher observes an increase in the release of a neurotransmitter known to inhibit the globus pallidus internus. Which of the following amino acids is the released neurotransmitter derived from? | ||
|Explanation=The [[caudate]] is involved in the direct and indirect pathways of the fine tuning of motor activity. The caudate is physiologically stimulated by [[glutamate]] released from the motor cortex. Stimulation of the caudate, physiologically or experimentally, will likely lead to the release of [[GABA]]. GABA is an inhibitory neurotransmitter derived from [[glutamate]]. The synthesis of GABA requires [[vitamin B6]]. | |Explanation=The [[caudate nucleus]] is involved in the direct and indirect pathways of the fine tuning of motor activity. The [[caudate nucleus]] is physiologically stimulated by [[glutamate]] released from the motor cortex. Stimulation of the [[caudate nucleus]], physiologically or experimentally, will likely lead to the release of [[GABA|gamma-aminobutyric acid (GABA)]]. [[GABA]] is an inhibitory neurotransmitter derived from [[glutamate]]. The synthesis of [[GABA]] requires [[vitamin B6]]. | ||
|EducationalObjectives= [[GABA]] is synthesized from [[glutamate]] using the enzyme L-glutamic acid decarboxylase and [[pyridoxal phosphate|pyridoxal phosphate (vitamin B6)]] as a cofactor. | |||
|References= First Aid 2014 page 110 | |||
|AnswerA=Tryptophan | |AnswerA=Tryptophan | ||
|AnswerAExp=[[Tryptophan]] is not a precursor for GABA. | |AnswerAExp=[[Tryptophan]] is not a precursor for [[GABA]]. | ||
|AnswerB=Glycine | |AnswerB=Glycine | ||
|AnswerBExp=[[Glycine]] is not a precursor for GABA. | |AnswerBExp=[[Glycine]] is not a precursor for [[GABA]]. | ||
|AnswerC=Glutamate | |AnswerC=Glutamate | ||
|AnswerCExp=Glutamate is the precursor for GABA, the synthesis of which requires vitamin B6. | |AnswerCExp=[[Glutamate]] is the precursor for [[GABA]], the synthesis of which requires vitamin B6. | ||
|AnswerD=Arginine | |AnswerD=Arginine | ||
|AnswerDExp=[[Arginine]] is not a precursor for GABA. | |AnswerDExp=[[Arginine]] is not a precursor for [[GABA]]. | ||
|AnswerE=Lysine | |AnswerE=Lysine | ||
|AnswerEExp=[[Lysine]] is not a precursor for GABA. | |AnswerEExp=[[Lysine]] is not a precursor for [[GABA]]. | ||
|RightAnswer=C | |RightAnswer=C | ||
|WBRKeyword=Basal ganglia, GABA, glycine | |WBRKeyword=Basal ganglia, [[GABA]], glycine | ||
|Approved=No | |Approved=No | ||
}} | }} | ||
Revision as of 19:23, 7 October 2014
| Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::A researcher investigating the regulatory neurotransmitters in the basal ganglia sends high frequency electrical impulses into specific areas of the brain of a rat and measures the change in the local concentration of several neurotransmitters. Upon stimulation of the caudate, the researcher observes an increase in the release of a neurotransmitter known to inhibit the globus pallidus internus. Which of the following amino acids is the released neurotransmitter derived from?]] |
| Answer A | AnswerA::Tryptophan |
| Answer A Explanation | [[AnswerAExp::Tryptophan is not a precursor for GABA.]] |
| Answer B | AnswerB::Glycine |
| Answer B Explanation | [[AnswerBExp::Glycine is not a precursor for GABA.]] |
| Answer C | AnswerC::Glutamate |
| Answer C Explanation | [[AnswerCExp::Glutamate is the precursor for GABA, the synthesis of which requires vitamin B6.]] |
| Answer D | AnswerD::Arginine |
| Answer D Explanation | [[AnswerDExp::Arginine is not a precursor for GABA.]] |
| Answer E | AnswerE::Lysine |
| Answer E Explanation | [[AnswerEExp::Lysine is not a precursor for GABA.]] |
| Right Answer | RightAnswer::C |
| Explanation | [[Explanation::The caudate nucleus is involved in the direct and indirect pathways of the fine tuning of motor activity. The caudate nucleus is physiologically stimulated by glutamate released from the motor cortex. Stimulation of the caudate nucleus, physiologically or experimentally, will likely lead to the release of gamma-aminobutyric acid (GABA). GABA is an inhibitory neurotransmitter derived from glutamate. The synthesis of GABA requires vitamin B6. Educational Objective: GABA is synthesized from glutamate using the enzyme L-glutamic acid decarboxylase and pyridoxal phosphate (vitamin B6) as a cofactor. |
| Approved | Approved::No |
| Keyword | WBRKeyword::Basal ganglia, [[WBRKeyword::GABA]], WBRKeyword::glycine |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |