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NBME 20 Answers

nbme20/Block 4/Question#28 (41.2 difficulty score)
A 78-year-old man dies of chronic congestive ...
Failure of the Na+–K+ pump🔍
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 +11  upvote downvote
submitted by nwinkelmann(257),
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hiTs pliesxna ti lrelya lelw twhi a :ipcrute .wsa/ahtfou.elmelP/iopttdt:d.wmm/0o/AssAth2n.lthailsg/ylpthaw/1il.

yoHicrdp nacgeh = eno of eht erlya ginss of arlulcle idnntaeogeer in epeonssr to ruiyjn thta tlsrseu in anauultocmci fo ertwa ni het e.llc a/piaheoixsmiycH dalse to ecdsaee in aecbior tirrpieoasn in the oncrdtaiimoh dna reeacedsd APT onptiduocr due to filaure fo het +/aN+K eTaAsP gindael to Na+ and wrate udoifnfis iont het lcel. daIulvdiin tubelu slcel peraap enowlsl dan mep""yt hwti lmaots cdclodue le,mnu mgeouulsrl is ullrpalyherec.

dickass  it's basically from pathoma chapter 1: cellular injury causes swelling +4  
md_caffeiner  @dickass you why arent you on every q stem? +1  
mangotango  do you mean "causing failure of the Na+/K+ ATPase" instead of "due to failure of Na+/K+ ATPase..." ? The low ATP is due to dec aerobic respiration, I believe. +1  
fatboyslim  @Mangotango yes exactly. Na/K ATPase stops working due to the lack of ATP. I think nwinkelmann mixed it up +  



 +5  upvote downvote
submitted by xxabi(224),
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hwnilo  elgtSef o(,l pcregli.cdyh. e cined)a he soeern:s teiuaitim→gs  apue PtrdoTcdreidnAeosc ecaA sr→ aaePdee NTa /dK+nsd+ +Cppm2ua soniaitdyf ot  ic→fivfu N+ anda werat n ttioeh lcl→e  lacllig rlnselwue

endochondral1  can someone explain how to cross out the other choices> +1  
endochondral1  what is hydropic degneration and where do i learn about it? why is it not the loss of plasma membrane integrity? +1  
shaeking  Endochondral1, I had the same question. I tried figuring it out and this is what I came up with. The CHF and congestion of the lungs is reducing the amount of oxygen getting to the renal cells. With hypoxia there is decreased aerobic resp in mitochondria with decreased ATP. Without ATPase Na builds up and water follows. As far as the loss of membrane integrity. I think it would cause cellular destruction not just hydropic changes. This is my best guess. +2  
charcot_bouchard  Membrane damage is irreversible stage of cellular injury. if membrane is damaged cell is dying & it will shrink. or totally destroyed by inflammation. they are specifically asking hydropic changes ie cellular swelling. which is the 1st sign of reversible cell injury due to failure of Na/K pump +1  
winelover777  @endochondral1 Chapter 1 of Pathoma. Also FA 2019 p207 describes hydropic degeneration without saying those exact words in the first bullet under reversible cell injury. +1  



 +0  upvote downvote
submitted by qfever(28),

Pathoma 2018 edition page 4 chapter 1 - Cellular Injury - III. Reversible & irreversible cellular injury - B.1.

I had difficulty trying to figure out what hydropic change means though...

bharatpillai  i swear i've done the same question before on uworld/ one of the previous NBMEs and the answer to that was intracellular Ca accumulation. +1  
mangotango  @bharatpillai that's also true! Dec ATP >> dec activity of Ca2+ and Na+/K+ pumps >> cellular swelling (earliest morphologic manifestation of reversible cell injury), mitochondrial swelling --- FA, pg 207 Na+/K+ ATPase inhibited >> inc intracellular Na+ >> dec activity of Ca2+/3Na+ exchange pump >> inc intracellular Ca2+ --- this is the same way digoxin works in the heart! +