WBR0543
Jump to navigation
Jump to search
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::A 32-year-old male is brought to the emergency room with a decreased level of consciousness. Vital signs demonstrate a temperature of 36.3 °C, heart rate of 44 bpm, respiratory rate of 6 breaths/min, and blood pressure of 100/60 mmHg. Upon physical examination, the patient is difficult to arouse, has pinpoint pupils and track marks on his arm. You suspect drug abuse. Which of the following mechanisms corresponds to the pupillary constriction in this patient?]] |
| Answer A | AnswerA::Activation of gamma-aminobutyric acid (GABA) receptors in the geniculocalcarine radiations |
| Answer A Explanation | AnswerAExp::GABA and the geniculocalcarine radiations have no role in pupillary constriction. |
| Answer B | AnswerB::Activation of opioid receptors in the Edinger-Westphal nucleus |
| Answer B Explanation | AnswerBExp::See overall explanation. |
| Answer C | AnswerC::Activation of glutamate receptors in the lateral geniculate nucleus |
| Answer C Explanation | AnswerCExp::GABA and the The lateral geniculate nucleus have no role in pupillary constriction. |
| Answer D | AnswerD::Activation of opioid receptors in the superior colliculus |
| Answer D Explanation | AnswerDExp::The superior colliculus is not responsible for pupillary constriction. |
| Answer E | AnswerE::Activation of GABA receptors in the oculomotor nerve |
| Answer E Explanation | AnswerEExp::GABA has no role in pupillary constriction. Although the oculomotor nerve is involved, due to the activation of receptors in the Edinger-Westphal nucleus, the activated receptors are of opioid type, not GABA. |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Opioid analgesic overdose is life-threatening and affects multiple organ systems. Opioids increases the activity of G-protein-coupled transmembrane mu, delta, and kappa opioid receptors in various organs. Heterodimer and homodimer receptors form to activate endogenous and exogenous compounds. Patients with opioid overdose are frequently present with a comatose-like condition with signs of cardiopulmonary depression, such as low heart rate, low respiratory rate, and low blood pressure. Upon physical examination, patients with chronic abuse of opioids may have visible track marks on their arms and characteristic pinpoint pupils.
Opioid receptors in the brain stem mediate the respiratory depression in patients with opioid toxicity. Pinpoint pupils occur following the activation of the opioid receptor in the Edinger-Westphal nucleus of the oculomotor nerve. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::opioid toxicity, WBRKeyword::Edinger-westphal, WBRKeyword::pupillary, WBRKeyword::pupillary constriction, WBRKeyword::morphine, WBRKeyword::drug overdose, WBRKeyword::addiction, WBRKeyword::optical, WBRKeyword::drug abuse |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |