UWorld_4.2

Question 1

Calculation of absolute risk percent

Answer 1

• ARP = 100 * (risk in exposed - risk in unexposed)/risk in exposed
• ARP = 100 * (RR-1)/RR

Question 2

Aging effects on aortic valve

Answer 2

• aging ==> cell death/necrosis ==> physiologic calcification in the setting of normal calcium levels
• aortic sclerosis = common in elderly adults
• can progress ==> calcified aortic stenosis = outflow obstruction

Question 3

Glucagon receptor type + other hormones w/same receptor

Answer 3

• G-protein coupled receptor
• binding ==> activated Adenylate Cyclase ==> increased cAMP ==> activated PKA
• other hormones
  
  • PTH
  • B-andrenergic
  • TSH

Question 4

Aoritc regurgitation murmur

Answer 4

• early diastolic murmur

Question 5

Nitrate adverse effects + prevention

Answer 5

• ==> reflex tachycardia due to relative hypotension
• prevented with beta-blockers

Question 6

Metoprolol effects

Answer 6

• B1 selective blocker
  
  • present @ heart & JGA
• ==> decreased HR
• ==> blocks renin release by JGA cells

Question 7

Phenotypic mixing definition

Answer 7

• co-infection of cells with two viruses ==>
• next gen: one virus obtains nucleocapsid proteins from one virus and contains the genome of the other
• since no change in underlying genome ==> next gen of progeny revert back to original phenotype

Question 8

Skin finding in Pseudomonas bacteremia

Answer 8

• ecthyma gangrenosum = cutaneous necrotic disease
• pseudomonas releases exotoxin ==> bv damage ==> ischemia & necrosis @ skin

Question 9

Beta-thallesemia mutations ==>

Answer 9

• defective transcription, processing, or translation of b-globin mRNAs ==> deficiency in quantity/quality of b-globin genes needed to synthesize hemoglobin

Question 10

Chediak-Higashi presentation

Answer 10

• defect in PMN lysosome fxn ==>
• neurologic defects
  
  • nystagmus
• partial albinism
  
  • due to abnormal melanin storage
• immunodeficiency
  
  • recurrent pyogenic infections, usually staph or strep

Question 11

Most common urea cycle defect

Answer 11

• defiency of Ornithine transcarbamoylase: ornithine + carbamoyl phosphate ==> citrulline in mitochondria
• ==> increased blood ammonium levels + increased urinary exrection of orotic acid

Question 12

V2 effects @ medullary collecting duct

Answer 12

• ==> increased permeability to H20 and urea

Question 13

Initial treatment of severe hypoglycemia

Answer 13

• in the field/@home:
  
  • less severe (mild-moderate) ==> fast-acting carbs; e.g. fruit juice, glucose tablet
  • unconscious: IM glucagon
• @ hospital: IV glucose

Question 14

Tx for combined T-C and absence seizures

Answer 14

• valproic acid

Question 15

Baroreceptor afferent nerve conduction

Answer 15

• Carotid baroreceptor info = CN IX (glossopharyngeal)
• Aortic baroreceptor info = CN X (vagus)

Question 16

Net excretion calculation =

Answer 16

Net excretion (A) = (inulin CL)(plasma concentration(A)) - tubular reabsorption (A)

Question 17

Winter’s formula + use

Answer 17

• PaCO2 = [1.5 * HCO3-] + 8 +/-2]
• if PaCO2 is greater than winter’s calculation = indication of inability to produce respiratory alkalosis to compensate for metabolic acidosis

Question 18

Amphotericin B: SE

Answer 18

• Nephrotoxicity and electrolyte abnormalities
• ==> hypoK and hypoMG
• hypoK ==> T wave flat, ST-depression, U waves

Question 19

Bethanacol: MOA

Answer 19

musc. antagonist

Question 20

high vs. low selective proteinuria

Answer 20

• high = albumin & ferritin only (LMW)
• low = albumin + Ig + macroglob

Question 21

Coll. synth defect in OI

Answer 21

• defect in procollagen peptidase ==> defect in C/N terminal protein cleavage

Question 22

“Foamy” or “Frothy” urine ==> dx?

Answer 22

proteinuria or bile salts in urine

Question 23

RCC clear cell lineage

Answer 23

proximal tubule cells

Question 24

Calcinuerin fxn

Answer 24

• calc = protein phosphatase ==> dephosph NFAT ==> trxn factor for IL-2 ==> T cell growth and maturation
• Cyclosporine & Tacrolimus ==I calcineurin ==> anti-rejection/immunosuppress drugs

Question 25

Unfractionated vs. LMWH

Answer 25

• unfractionated = binds ATIII and allows activity against factor Xa and thrombin (inactivation)
• LMWH ==> ATIII activity against Xa only

Question 26

Parvovirus @ children vs. adults

Answer 26

• @ children: fever, malaise + erythema infectiosum = rash on cheeks; rahs may also be present extremities ==> trunk
• @ adults: arthritis in bilateral IP, metacarpal, knee and ankle joints
  
  • resolves spontaneously (unlike RA)

Question 27

Liver (unique) processing of triglycerides

Answer 27

• @ adipose tissue: lipase: triglycerides==> glycerol + FFA
• @ liver: glycerol kinase: glycerol ==> glycerol-3-P ==> DHAP ==> gluconeogen or glycosis

Question 28

Lymph drainage to superficial inguinal lymph nodes

Answer 28

• all lower extremities, except calf
• umbilicus to feet w/external genitalia and anus

Question 29

Insulin receptor mechanism

Answer 29

• insulin ==> tyrosine kinase ==> insulin receptor substrate phosphorylization ==> activation of protein phosphatase
• protein phosphatase ==> dephosph glycogen synthase = activated glycogen formation
  
  • also ==> dephosph of fructose-1,6-bisphosphatase = inactive ==> inhibition of gluconeogenesis

Question 30

Most abundant amino acid in collagen

Answer 30

glycine (at least every third)

Question 31

Tongue innervation

Answer 31

• Motor = CN XII
  
  • except palatoglossus m. = CN X
• Sensory
  
  • Ant 2/3 = CN V3 (mandibular)
  • Post 1/3 = CN IX
  • Post. root/pharynx = CN X
• Taste
  
  • Ant 2/3 = CN VII (chorda tympanii)
  • Post 1/3 = CN IX
  • Post. root/pharynx = CN X

Question 32

Succinylcholine: MOA, use

Answer 32

• MOA: depolarizing NMJ blocker
• use: rapid induction/intubation or for surgical intubation
• phase I = augmented by AChEi (e.g. neostigmine)
• phase II = reversed by AChEi