6/22 UWorld

Question 1

Nerves involved in pupillary light reflex

Answer 1

CN II = afferent signal

CN III = eferent signal

• Sequence of events:
  
  • Light in either retina = signal via CN II (optic) to pretectal nuclei in midbrain = activation of bilateral Edinger-Westphal nuclei = signal from EW nuclei to ciliary ganglion via CN III (oculomotor) = bilateral pupillary constrictor muscle activation

Question 2

Afferent and efferent nerves of corneal reflex

Answer 2

• Afferent = CN V1
• Efferent = CN VII

Question 3

What does “power” of a test tell you

Answer 3

• Probability that the test will correctly reject the null hypothesis, when it is indeed false
• Aka the likelihood that you will correctly identify a difference when one does exist

Question 4

In what disease do you see Orphan Annie nuclei

Answer 4

Papillary carcinoma of the thyroid

Question 5

Which hernia is medial/lateral to inferior epigastric vessels - direct vs. indirect

Answer 5

THINK: MD’s don’t LIe

Direct = medial

Indirect = lateral

Question 6

MOA of Carbidopa vs. COMT inhibitors

Answer 6

• Carbidopa = inhibits peripheral conversion of DOPA to DA, so DOPA can head to brain
  
  • Does not cross BBB
• COMT inhibitors = inhibits conversion of DOPA to inactive metabolite
  
  • Tolcapone works both peripherally and centrally

Question 7

MOA of Ropinirole

Answer 7

D2 receptor agonist

Question 8

MOA of Pramipexole

Answer 8

D3 receptor agonist

Question 9

Location of bile acid reabsorptino

Answer 9

Ileum

Maybe have decreased reabsorption in Crohns (affects terminal ileum), leading to increased ratio of cholesterol to bile within bile acid, thus predisposing to gallstones

Question 10

What is the mutation caused by aflatoxin that leads to hepatocellular carcinoma

Answer 10

p53 mutation

Question 11

What type of reactions are vitamin B6 used in

Answer 11

Transamination (ALT and AST)

Question 12

What type of reactions is biotin (B7) used in

Answer 12

Carboxylation

Question 13

Where is the cell does Vitamin C play a role in collagen synthesis?

Answer 13

Rough ER

Collagen synthesis:

• o Signal sequence directs growing polypeptide chain into endoplasmic reticulum
• o Signal sequence is cleaved
• o Hydroxylation of selected proline and lysine residues (vitamin C dependent)
• o Glycosylation of selected hydroxylysine residues
• o Assembly of pro-alpha-chains into procallagen triple helix
• o Procollagen transferred to Golgi apparatus and secreted into extra cellular matrix
• o Terminal propeptides cleaved by N- and C- procollagen peptidases
• § Ehlers Danlos can be caused by a deficiency in procollagen peptidase, leading to soluble collagen that does not properly crosslink
• o Collagen molecules spontaneously assemble
• o Covalent cross links formed by lysyl oxidase

Question 14

Where in the cell/what enzyme in collagen synthesis is the problem of Ehlers Danlos

Answer 14

Extracellular matrix

• Terminal propeptides cleaved by N- and C- procollagen peptidase
  
  • Ehlers Danlos can be caused by a deficiency in procollagen peptidase, leading to soluble collagen that does not properly crosslink

Question 15

What muscle is often associated with compression of the sciatic nerve

Answer 15

Piriformis

Question 16

What part of the penis does Sildenafil work on?

Answer 16

Vasodilation leads to increased bloodflow into corpus cavernosum

Question 17

MOA of Ras as an oncogene

Answer 17

Oncogene = is a signal transducer (GTP-binding protein)

• o Ras is associated with growth factor receptors in an inactive GDP-bound state
• o Receptor binding causes GDP to be replaced with GTP, activating Ras
• o Activated Ras sends growth signals to the nucleus
• o Ras inactivates itself by cleaving GTP to GDP via GTPase protein
• o Mutated Ras inhibits the activity of GTPase, thus producing a prolonged activated state of Ras

Question 18

Crohn’s vs. Ulcerative colitis

Histology

Answer 18

Crohn - noncaseating granulomas with lymphoid aggregates

UC - crypt abscesses with neutrophils

Question 19

What is Trousseau syndrome

Answer 19

Caused by pancreatic adenocarcinoma

• Hypercoagulability
• Venous thrombosis
• Migratory thrombophlebitis

Question 20

Describe primary sclerosing cholangitis

Answer 20

• Concentric fibrosis of the intra- and extra-hepatic bile ducts
• Contrast imaging will show “beaded” appearance due to alternating fibrotic and dilated regions
• Mostly occurs in men around age 40
• Associated with (+) pANCA and Ulcerative colitis
• Increased risk for cholangiocarcinoma

Vs. Primary biliary cholangitis which is autoimmune (anti-mitochondrial) with lymphocytes/granulomas

Question 21

Describe fluid compartment/composition of body

Answer 21

• 60-40-20 rule
• 60% of body mass is water, of that 60%:
  
  • 40% is ICF
  • 20% is ECF
    
    • Only 25% of ECF is plasma

Question 22

When does glucose begin to appear in the urine

Answer 22

• Glucose is completely reabsorbed up until plasma glucose level ~200 mg/dL
  
  • This is when glucosuria begins (threshold)
• At ~375 mg/min, all transporters are fully saturated

Question 23

Describe the defect in type 1 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 23

• Distal renal tubular acidosis à defect in collecting tubule
• Alpha-intercalated cells are unable to secrete H+ à acidosis
• Hypokalemia
• Urine pH will be > 5.5 (because no H+ in urine)
• Causes:
  
  • Amphotericin B toxicity, analgesic nephropathy, congenital anomalies (obstruction) of urinary tract

Question 24

Describe the defect in type 2 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 24

• Proximal renal tubular acidosis à defect in proximal tubule
• Impaired HCO3- reabsorption à Increased HCO3- excretion à acidosis
• Hypokalemia and hypophosphatemia
• Urine pH < 5.5 (urine is acidified by a-intercalated cells in collecting tubule)
• Causes:
  
  • Fanconi syndrome, carbonic anhydrase inhibitors

Question 25

Describe the defect in type 4 renal tubular acidosis, hyper/hypokalemia, urine pH

Answer 25

* Hyperkalemic renal tubular acidosis * Due to hypoaldosteronism à decreased K+ secretion à hyperkalemia * Hyperkalemia prevents collecting tubules from generating NH4+ à impaired ammonium excretion * Urine pH \< 5.5 (decreased aldosterone = decreased Na+ reabsorption = increased Na+ in lumen = positively charged lumen) * Causes: * Decreased aldosterone production (diabetic hyporeninism, ACE inhibitors, ARBs, NSAIDs, heparin, cyclosporine, adrenal insufficiency) * Aldosterone resistance (K+ sparing diuretics, nephropathy due to obstruction, TMP/SMX)

Question 26

What is fanconi syndrom

Answer 26

* Reabsorptive defect of the PCT * Associated with increased excretion of amino acids, glucose, HCO3-, and PO43- * Causes: * Hereditary defects, ischemia, multiple myeloma, nephrotoxins/drugs (cisplatin, tenofovir, expired tetracyclines), lead poisoning

Question 27

What is Winter's fomula and what does it do?

Answer 27

* Predicted respiratory compensation for metabolic acidosis * If measured pCO2 \> predicted pCO2 – concomitant respiratory acidosis * If measure pCO2 \< predicted pCO2 – concomitant respiratory alkalosis * pCO2 = 1.5(HCO3-) + 8 +/- 2

Question 28

MOA of alpha-toxin of C. perfringens

Answer 28

Toxin is a lecithinase - degrades lecithine, a component of phospholipid membranes, leading to cell death and necrosis

Question 29

Presentation of Alport syndrome

Answer 29

Presents as isolated hematuria, sensory hearing loss, and ocular disturbances “Can’t see, can’t pee, can’t hear high C”

Question 30

Where are immune complex depositions seen in diffuse proliferative glomerulonephritis

Answer 30

DPGN seen in Lupus Immune complexes seen subendothelially and within the mesangium

Question 31

What type of stone is a struvite stone?

Answer 31

Ammonium magnesium phosphate stone * Major risk factor = Urease + bacteria * Recall: * Urea is broken down by urease into NH3 and CO2 * NH3 converted to NH4+ which can combine with magnesium and phosphate

Question 32

Describe histology of renal cell carcinoma

Answer 32

Will see polygonal clear cells filled with accumulated lipids and carbohydrates

Question 33

Tumors that secrete EPO

Answer 33

* Potentially Really High Hematocrit * Pheochromocytoma * Renal cell carcinoma * Hepatocellular carcinoma * Hemangioblastoma

Question 34

What is WAGR complex

Answer 34

* Wilms tumor, Aniridia (absence of iris), Genitourinary malformation, mental/motor Retardation

Question 35

What disease is associated with thyroidization of the kidney

Answer 35

Chronic pyelonephritis Eosinophilic casts dilate the tubules, causing the tubules to have a colloid/thyroid-like appearance

Question 36

What disease is associated with eosinophils in urine

Answer 36

Acute interstitial nephritis Acute interstitial renal inflammation that results in acute renal failure Presentation: Fever, rash, eosinophilia, azotemia

Question 37

Describe medullary cystic disease

Answer 37

* Can lead to fibrosis and progressive renal insufficiency * Will present as cysts in the collecting ducts and shrunken kidney due to fibrosis * Vs. most other cystic diseases which will present with cystic dilation of kidney

Question 38

Describe the organ systems associated with each of the muscarinic receptors (M1, M2, M3)

Answer 38

M1 - enteric and CNS M2 - heart M3 - bladder, smooth muscles of eye

Question 39

What part of the nephron has most dilute urine

Answer 39

Distal convoluted tubule

Question 40

MOA of polyethylene glycol

Answer 40

Sketchy = PEG Osmotic laxative

Question 41

What is Meniere disease

Answer 41

* Increased pressure and volume of endolymph * Features: * Recurrent vertigo * Ear fullness/pain * Unilateral hearing loss and tinnitus

Question 42

MRI findings in multiple sclerosis

Answer 42

Periventricular plaques (areas of oligodendrocyte loss and reactive gliosis)

Question 43

Describe presentation of Vestibular neuritis

Answer 43

* Vestibular neuritis (labyrinthitis): * Inflammation of vestibular nerve * Features: * Single episode that can last days * Severe vertigo but no hearing loss

Question 44

Presentation of Creutzfeldt-Jakob disease

Answer 44

Rapidly progressive dementia + ataxia + startle myoclonus

Question 45

Homogentisate oxidase usually converts what to what?

Answer 45

Tyrosine to fumarate

Question 46

Describe the meaning of "permissiveness" in reference to drug-drug interaction

Answer 46

When drug 1 allows drug 2 to exert maximal effects But drug 1 alone does not have similar effects (that would be considered synergistic or additive)

Question 47

Deficiency of CD55 or CD59 indicates what disorder?

Answer 47

Paroxysmal nocturnal hemoglobinuria Due to deficiency of GPI, which usually anchors DAP (CD55) to RBC membrane to protect from complement destruction