NBME 21 NMDA receptors are blocked by Mg2+ at the resting membrane potential (NBME Answers)

NBME 21 Answers

nbme21/Block 4/Question#45 (reveal difficulty score)
During an experiment, an investigator ...
NMDA receptors are blocked by Mg2+ at the resting membrane potential 🔍 / 📺 / 🌳
tags: neuro magnesium pharm

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+64
submitted by gribear(0),

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anC eenomso eplaxin yhw nwhe ouy tcasrnet teh splnai docr ioreprus to the evlel of tsmtacehpiy owtlufo -- dna ouy get a scsmyeti ninfcoite -- the sreepsno si alaoenrtit fo het trhisttmcoea tse tnop?i

+55
submitted by ∗niboonsh(382),

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wmhacbzDtwwvco/houuoys4p.t?:w/-H/2=.tuwQetv fi ur ylza kiel em, tsih si a oogd sfheererr odvei

d_holles Amazing video dude. Somehow never learned this in neuro lol. +7

aag Awesome video! Is this why you can give Mg2+ to eclampsia patients, because if so, mind goddamn blown. +3

+5
submitted by ∗cantaloupe5(85),

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ihsT oen was itrkcy ubt I nhikt yuo evdulo’c dnoe tihs noe woithut dkngeeolw fo NAMD epecr.tors tmeS tldo yuo that ettaaulgm tcvataeis hobt nMDAn-oN adn ADMN ererpsoct utb it tvctaeida nylo DMAnNn-o eopscertr ni teh lraey ae.sph aTth mneas ADNM ocsepetrr vcttaiea featr onN-MnDA se.torcper Ttha eanms gtohsmnie wsa deygnlia NDAM eeorrcpt tiicnatvga nda eht lnoy awrsen ahtt edam eesns sa eht Mg hbntgniiii DAMN ta igrtnse etpiolnta. Once hte llce is erpizdedlao by -NnMDAon eretosprc, ADNM rereocspt nca eb dvia.tacet

hungrybox I forgot/didn't know this factoid and narrowed it to the correct answer and a wrong answer. Guess which one I chose? +15

yotsubato >That means something was delaying NMDA receptor activating and the only answer that made sense as the Mg inhibiting NMDA at resting potential. What makes the fasting gating kinetics choice incorrect then? +5

imgdoc NMDA receptors are both voltage gated and ligand gated channels. Glutamate and aspartate are endogenous ligands for this receptor. Binding of one of the ligands is required to open the channel thus it exhibits characteristics of a ligand channel. If Em (membrane potential) is more negative than -70 mV, binding of the ligand does NOT open the channel (Mg2+ block on the NMDA receptor). IF Em is less negative than -70 mV binding of the ligand opens the channel (even though no Mg2+ block at this Em, channel will not open without ligand binding. Out of the answer choices only NMDA receptors blocked by Mg2+ makes sense. Hope this helps. +6

divya sweet explanation imgdoc +

lovebug really~~~ sweet. thankyou :) +

+3
submitted by ∗sweetmed(150),

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At etrigns braemenm tilepnoat eth NMDA cpetrerso are oebcdkl yb 2.M+g eTh vlotaeg epedtdnen g+2M lcbko si eerdlive oupn tndriopaiaoelz fo hte t-opitsnapcys rmnemeab . The adglin tdedepenn acotinvtia fo eht DAMN toerecrp iureeqrs itotinaao-cvc by wto la,gsndi lnymae ealagumtt nda nlie.gyc

+0
submitted by ∗okokok1(29),

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nA mttiopanr tearled inlialcc lpatiipcano si rbre:mmgiene aOivran taaroemt dan tirhe catinisosaos ti:wh -itDMANAn erecotrp nes.taihelicp Tish spenster :as hicPirtyacs saibc,truedn yomerm itcefsid, re,esuisz yeiskdsnasi, ouaonticm ,lisynaiibtt galngeau ytidnns.fouc

AF: ;2020 pg 282

-1
submitted by vlodkadrinker(7),

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dno't oetrgf tbuoa eht Mg b!kocl . . . . . .

chandlerbas https://www.youtube.com/watch?v=-mHgPfXHzJE +3