UWorld_3.29

Question 1

Mechanism ==> decreased RBF and increased FF

Answer 1

constriction of efferent arteriole

Question 2

Pathophysiology of narcolepsy

Answer 2

-low levels of NT orexin (hypocretin) which normally promotes wakefullness & suppresses REM sleep phenomenon

Question 3

Positive cyanide-nitroprusside urine test ==> dx?

Answer 3

-cysteinuria = defect of cysteine transporters @ proximal renal tubule - ==> recurrent gallstones @ young age

Question 4

Metyrapone stimulation test purpose/mechanism

Answer 4

-tests integrity of HPA axis -blocks cortisol synthesis via inhibition of 11B-hydroxylase -decreased neg. feedback ==> ACTH surge

Question 5

Antidote for NE drip-mediated tissue necrosis

Answer 5

-alpha-1 receptor blocker -e.g. phentolamine

Question 6

Tx of calcium oxalate kidney stones

Answer 6

hydrochlorothiazide: blocks Na/Cl transporter @ lumen ==> activation of Na/Ca exchanger ==> increased Na w/in cell in exchange for increased Ca reabsorbed

Question 7

How does s. viridans adhere to valves ==> endocarditis?

Answer 7

-previous valve damage + fibrin deposition is required to adhere

Question 8

Formation of env HIV genes

Answer 8

glycosylation ==> gp160 + proteolytic cleavage @ ER ==> gp120 + gp41 = mediators of target fusion

Question 9

Mechanism of C. diff exotoxins

Answer 9

-toxins A & B -disruption of Rho-regulatory proteins & actin cystoskeleton elements ==> impaired cytoskeleton maintence - + disruption of tight jxns -A = more enterotoxic -B = more cytotoxic

Question 10

Only sensory pathway that doesn’t relay through thalamus

Answer 10

smell

Question 11

Cavitary lesion in lung + air fluid levels on xray ==> dx?

Answer 11

lung abscess (possibly aspiration pneumo)

Question 12

Adenosine: MOA, use, SE

Answer 12

-MOA: slowing conduction through AV node by hyperpolarizing nodal & conducting cells -use: drug of choice in paroxysmal SVT -SE: flushing, chest buring (bronchospasm), hypotension, high-grade AV block