share email twitter ⋅ join discord whatsapp(2ck)
free120  nbme24  nbme23  nbme22  nbme21  nbme20  nbme19  nbme18  nbme17  nbme16  nbme15  nbme13 

NBME 21 Answers

nbme21/Block 2/Question#26 (44.1 difficulty score)
A healthy 32-year-old woman at 35 weeks' ...
Birth canal reflexπŸ”
tags:

Login to comment/vote.


 +14 
submitted by hayayah(1057),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

tctehrS or ailtonid fo the rcxevi dna ganiva rae rstogn lmiusti rfo oxnytioc nstre,cioe iameedtd yb rnulea spahtwya llcdea hte snoFurge lreexf.

ilA:tecr eoec/.c-wlriew:isrcisxrucceunt/.tcnefepso/woied/gepmefsohnntcrt/s

readit  This is also why ob-gyn's will massage the uterus (which is part of the birth canal) after delivery. It's to get the body to release oxytocin and cause the uterus to contract (to prevent postpartum hemorrhage) +5  
jennybones  Please why is estrogen not the answer, I thought estrogen would upregulate oxytocin receptors and increase oxytocin secretion? +1  
drzed  During pregnancy, oxytocin RECEPTORS are upregulated (by estrogen) as parturition approaches, but the ferugson reflex creates a positive feedback loop where the dilation of the cervix further releases more oxytocin. The inciting event that starts this feedback loop is the dilation of the cervix leading to a direct release of oxytocin, not the presence of more oxytocin receptors. +3  
bbr  To add, the positive feedback loop here is pretty elegant. Basically, it seems like the cervix doesnt want anything in it. When its stretched --> oxytocin --> contract uterus --> push baby --> more stretch at cervix---> more oxytocin (and forward). The positive feedback loop aspect is that oxytocin-based contractions cause more dilation of the cervix (as the baby moves into it!). +1  



 +0 
submitted by medschoollovin(14),
unscramble the site ⋅ remove ads ⋅ become a member ($39/month)

"Uopn iioappltcan fo sseurepr ot het rnieatnl end fo eht rvcx,ie otinyocx si eedalrse r(eferheto ransciee ni cnttlaiorec iset)ronp, wchhi leistastum renutei sotatroinnc,c hihcw ni rnut encesrias urespsre no eht ecrvxi be(rehty aginrescni cytooxin s,leeaer e.,ct) itnlu het byab si iddevreel.

oensSry ftnnorioiam gdgnrarei lnaecihmca cstrhet fo eth vxcier si eirdcar in a ssnyore une,nor hhwic pesnssay in the rdlsoa hnor breofe dasencign ot teh nirba in eht nlertaeroltaa omcluns aleiilast(rp nda lrrtoaetlacna es)urot. iVa het andime roneifbar lnbd,ue het fenfeetr rcaeehs eth NPV nda ONS of the uplahsotay.hm heT psoieorrt iiutrtpay elsaeesr tycoionx due to cneesrdia riigfn in eht oehm-ohplayoypytlasphah ct.atr xitOcyon tasc no het trummymoie, no creroespt chhiw ahve eben tdpuaeeglru by a facilunton nsiceera of hte tggrseenosnreeptoe-or rioa.t hisT ioafclnutn atoir naeghc is diamdeet by a csdaeree ni ieayrtmmol sivtsytiien to ntrseeropgeo, deu ot an neseiacr ni oenregopsrte rereocpt A, dan a nrnccutore sinercea in lateyrmmio etisyvsntii ot ogetersn, ude to na iaecsenr ni neegrsot cteprreo Ξ±. sihT secsau mmtyraolei coinotrncat dan huerfrt espotivi bacdfkee no hte 1elerx["f.]

ahif_w:tipisnpglekok/nuirwdse/r.oeixgF/r/te.e

seagull  https://www.ncbi.nlm.nih.gov/pubmed/8665768 a counter argument for PGE if you chose that answer. However, the author believes oxytocin is superior. +  
usmleuser007  1) PGE rises initially that causes the uterine contractions= this would be equivalent to when someone say #of contractions per time period. 2) Oxytocin is increased when the cervix is manipulated (ie. the birth canal reflex). +6  
jennybones  Please why is estrogen not the answer, I thought estrogen would upregulate oxytocin receptors and increase oxytocin secretion? +