NBME form 15

Question 1

CN3 palsy

• phenotypes (2)
• etiology

Answer 1

• two major phenotypes
  1. down-out gaze
  2. ptosis (levator palpebrae)
  3. mydriasis (parasympathetic peripheral)
• post.communicating artery aneurysm (this was answer)
• dumb mistake: Even though I knew question was asking about CN3 defect, I picked optic nerve, CN2.
  OPTIC NERVE IS NOT SAME AS OCCULOMOTOR
• Always think other choices carefully: CN3 palsy can happen with
  1. cavernous sinus syndrome
  2. Post. communicating artery aneurysm (think where it runs)

Question 2

Inheritance pattern of cystic fibrosis?

Answer 2

autosomal recessive

• I thought one allele defect in CTFR gene is enough. But no. remember, it is protein folding defect. With one normal CTFR gene, it should be enough to cover one wrong allele.

Question 3

life style modification for duodenal ulcer?

Answer 3

stop smoking

• I picked decrease caffeine and fatty food.
  : duodenal ulcer etiology is due to increased gastric acid secretion. gastric acid is not associated with fatty food digestion. it is protein.

Question 4

What is oxyphil cells?

Answer 4

cells of parathyroid

Question 5

midline neck mass that moves with swallowing: diagnosis?

Answer 5

thyroglossal duct

• 99m pertechnetate uptake will be located in the mass
• 99m pertechnetate uptake is done by various tissues including thyroid, gallbladder, gastric mucosa/ pancreatic tissue (Merckel diverticulum)
  : it is NOT JUST LIMITED TO Merckel diverticulum

Question 6

Insecticide intoxication: what is first step that needs to be done immediately

Answer 6

atropine

• I was debating between atropine and pralidoxime. I thought pralidoxime, but patient is showing respiratory distress and salivation. Because patient already shows some sings of BB SLUDGE, immediate antidote should be given first

Question 7

zanamivir: MOA?

Answer 7

inhibitor of influenza neuroaminidase
: inhibition of virion (progeny) release

• neuraminidase inhibitor suffix: - mivir
• another drug with same mechanism is oseltamivir

Question 8

Role of IκB in the nuclear factor-kappa B (NF-κB) signal transduction pathway

Answer 8

Releases NF-kB after undergoing phosphorylation

Question 9

why deoxygenated blood can carry more carbon dioxide for a given Pco2 than oxygenated blood?

Answer 9

Deoxyhemoglobin is a better buffer of hydrogen ions than oxyhemoglobin

• I picked that CO2 and O2 compete same binding site: no this is wrong!!
• MAJORITY of CO2 does not actually bind to Hb, rather it is transformed to H+ and HCO3- (via CA). so it is HCO3- that represents how much CO2 is taken by Hb

Only small portion (5%) of CO2 binds to Hb as Hb-CO2 form. CO2 binds to Hb at N-terminus of globin, NOT HEME

• it is CO that directly competes Hb binding site in Hb, not CO2

Question 10

TSH: binds to what receptor

T3/T4: binds to what receptor

Answer 10

TSH: G protein coupled receptor

T3/T4: works like steroid. intracellular receptor that translocalizes to nucleus

Question 11

Which drug is used to kill hypnozoites of malaria (p.vivax/ovale)

Answer 11

primaquine

*PRIMaquine= PRIME drug for sleeping bug

Question 12

hemorrhagic macules on hair follicles: what disease is this?

Answer 12

scurvy

Question 13

What is normal heart weight?

Answer 13

300g
atheletes can go upto 500g

• question gives vague picture and states heart weight 650g. so it is hypertrophy

Question 14

HSV: latent in where?

Answer 14

SENSORY neuron (sacral ganglia)

• it is painful sensory to have HSV, so SENSORY
• i picked motor neuron