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USMLE Step 1 > High Yields Week 4 > Flashcards

High Yields Week 4 Flashcards

1
Q

What are the three phases of disease progression in Lyme disease (Borrelia burgdorferi infection)?

A
  1. Early phase - flu-like symptoms and erythema chronicum migrans (target looking rash)
  2. Early disseminated phase - CNS involvement (facial palsy) and/or cardiac involvement (AB nodal block)
  3. Late Lyme disease - asymmetric arthritis (typically a single knee joint) and/or encephalopathy with memory/mood changes
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2
Q

What are common side effects of nondihydropyridine calcium channel blockers (diltiazem, verapamil)?

A

Constipation
Bradycardia
AV conduction block (↓ chronotropic effect)
Worsening of HF in patients with reduced left ventricular systolic function (↓ inotropic effect)

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3
Q

What are the highlights of the three phases of syphilis (Treponema pallidum infection)?

A

Primary (3-5 wks) - painless chancre on genitals

Secondary (5-10 wks) - Diffuse macular rash that includes palms and soles, condylomata (gray wartlike lesions in genital/perianal area)

Tertiary (years later) - Gummas (white-gray rubbery lesion), ascending aortic aneurysm (vasa vasorum destruction), Argyll Robertson pupil (constricts w/ accommodation but not reactive to light)

Neurosyphilis (tabes dorsalis, “general paresis) can occur at ANY stage, but most common in tertiary

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4
Q

What is McCune-Albright syndrome?

A

Characterized by a triad of:

  • fibrous dysplasia of the bone (bony abnormalities, scar tissue in bone)
  • endocrine abnormalities (such as hyperthyroidism)
  • cafe-au-lait spots
  • precocious puberty in girls

Results from a mosaic G-protein signaling mutation causing constituitive activation of the G-protein/cAMP/adenylate cyclase signaling pathway

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5
Q

What is the mechanism of action of SSRIs?

A

Inhibition of serotonin reuptake into the presynaptic neuron, increasing the amount of serotonin in the synaptic space

This is done by blocking the “serotonin transporter”

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6
Q

A 45 y/o homeless man with a history of alcohol abuse presents to the ER with decreased urine output (oliguria), flank pain, metabolic acidosis and multiple calcium oxalate crystals in the urine. Disease/Dx?

A

Ethylene glycol ingestion

Causes metabolic acidosis, kidney stones and acute tubular necrosis (glycolic acid metabolite of ethylene glycol is toxic to renal tubules)

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7
Q

What is the most common type of thyroid cancer?

A

Papillary thyroid cancer

On histology - psammoma bodies, nuclear grooves and “Orphan Annie”

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8
Q

What is the inheritance pattern of MEN syndromes?

A

Autosomal dominant

“All MEN are dominant”

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9
Q

What is classically seen in MEN1?

A

3 P’s

Parathyroid tumors (↑ PTH → hypercalcemia
Pituitary tumors (prolactin, visual/mass effects)
Pancreatic endocrine tumors (usually gastrinomas → Zollinger-Ellison syndrome)
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10
Q

What is classically seen in MEN2A?

A

2 P’s

Medullary thyroid cancer (calcitonin)
Pheochromocytoma
Parathyroid hyperplasia

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11
Q

What is classically seen in MEN2B?

A

1 P

Medullary thyroid cancer (calcitonin)
Pheochromocytoma
Mucosal neuromas (skin colored lesions on lips/tongue)
Marfanoid habitus (long arms, long fingers, tall)

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12
Q

A 34 yo man presents with blue-black spots in his sclera and around his ears. He states that his urine turned black overnight after he forgot to flush the toilet. Disease/Dx?

A

Alkaptonuria

Autosomal recessive with deficient homogenistic acid dehydrogenase

This blocks the metabolism of tyrosine and causes an accumulation of homogenistic acid which is responsible for blue-black pigmentation discolorations

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13
Q

A 55 yo man presents with complaints of difficulty getting up from chairs and climbing stairs, diplopia, dry mouth and impotence. On physical exam he has decreased deep tendon reflexes. Chest x-ray notable for an irregular round mass in the upper lobe of his right lung. Disease/Dx?

A

Lambert-Eaton myasthenic syndrome secondary to small-cell carcinoma of the lung (classic association)

Lamert-Easton myasthenic syndrome is due to autoantibodies against the Ca2+ channels in the presynaptic terminal membrane that participate in acetylcholine release

Causes

  • proximal muscle weakness
  • cranial nerve involvement (diplopia, dysphagia)
  • autonomic dysfunction (dry mouth, impotence)
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14
Q

In the presence of ADH, where is the most concentrated fluid in the nephron? the most dilute fluid in the nephron?

A

Most concentrated → Collecting ducts (ADH mediates water absorption here, concentrating the urine)

Most dilute → thick ascending limb of Henle and distal convoluted tubule (impermeable to water with lots of electrolyte reabsorption, diluting the urine)

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15
Q

Where is airway resistance highest in the lungs?

A

The first 10 generations bronchi (small/medium bronchi)

This is due to all the turbulent airflow in these regions

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16
Q

As a class of drugs, what is the most common adverse effect associated with atypical (2nd generation) antipsychotics?

A

Metabolic adverse effects

  • WEIGHT GAIN
  • dyslipidemia
  • hyperglycemia
  • increased risk of diabetes
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17
Q

What main veins do the right and left ovarian veins drain into?

A

Right ovarian vein → IVC

Left ovarian vein → left renal vein (then draining to IVC)

This mimics the testicular veins

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18
Q

What causes the green discoloration seen in pus or coughed up sputum during common bacterial infections (such as Strep pneumo)?

A

The presence of myeloperoxidase

Myeloperoxidase is a blue-green enzyme released from neutrophils during an infection

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19
Q

What drug should be administered for acute exacerbations of COPD or asthma?

A

Beta-adrenergic agonists

B2-mediated relaxation of smooth muscle causes bronchodilation, opening the airways and providing relief of obstructive lung disease

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20
Q

Pancreatic beta cells contain adrenergic receptors a2 and B2. What are the effects of stimulation of these receptors on the pancreatic beta cells?

A

a2 stimulation → inhibits insulin secretion

B2 stimulation → promotes insulin secretion

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21
Q

What is the most common cause of death in tricyclic antidepressant (amitriptyline) overdose?

A

Cardiac arrhythmias and refractory hypotension

(due to inhibition of fast sodium channels in cardiac myocytes)

Treatment of TCA overdose is NaHCO3 (sodium bicarb)

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22
Q

What does the presence of Howell-Jolly bodies suggest?

A

Decreased or absent splenic function

Howell-Jolly bodies are RBCs that DNA remnant inclusions that are normally removed by the spleen during circulation

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23
Q

What do the RBCs of a patient with lead poisoning look like on a peripheral blood smear? on bone marrow aspirate?

A

Peripheral blood smear - RBCs with basophilic stippling (due to RNA aggregation)

Bone marrow aspirate - RBCs with ring sideroblasts (due to iron deposition)

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24
Q

What is the most common type of cancer in people chronically exposed to asbestos?

A

Lung cancer (bronchogenic carcinoma) is most common

Mesothelioma (pleural cancer) is second most common

Lung cancer > Mesothelioma

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25
Q

What cells does parvovirus B19 infect and replicate in?

A

Erythroid precursor cells in the bone marrow

This is why sickle cell patients develop aplastic crisis and immunosuppressed patients can develop chronic anemia with a parvovirus B19 infection

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26
Q

What type of morphology would be seen in an organ transplant rejection that has occurred slowly over months to years?

A
  • Vascular wall thickening and luminal narrowing
  • Interstitial fibrosis and parenchymal atrophy

TLDR - low grade, chronic immune response causing fibrosis to the organ; neutrophils/dense lymphocytic infiltrate will not be seen (those are seen in hyperacute and acute organ rejection)

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27
Q

What is indicative of intense regions of bright pink following acid-Schiff (PAS) stain on an intestinal biopsy of a 45 yo man presenting with abdominal discomfort, loose stools and recent weight loss?

A

Troperyma whippelii infection causing Whipple disease

PAS stain in conjunction with diastase stains the glycoprotein present in the cell walls of the gram-positive bacteria bright pink/magenta

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28
Q

Where do cranial nerves III, IV, V1 and VI exit the skull?

A

All of these nerves exit via the superior orbital fissure and provide motor (III, IV, VI) and sensory (V1) innervation to the eye

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29
Q

Describe first-order kinetics vs. zero-order kinetics in drug metabolism.

A

First-order - a constant PROPORTION of drug is metabolized per unit time - exponential metabolism
(ex. 50% of a drug metabolized per hour regardless of the drug concentration)

Zero-order - a constant AMOUNT of drug is metabolized per unit time - linear metabolism
(ex. 5mg of a drug is metabolized per hour regardless of drug concentration)

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30
Q

What is isolated systolic hypertension?

A

Systolic BP > 140 mm Hg + Diastolic BP 60yo, can be caused by increased arterial/aortic stiffness

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31
Q

A 35 y/o male presents with complaints that he cannot extent his right wrist. He does not recall any recent traumatic injury. He has a history of asthma. Lab values show eosinophilia and positive antibodies against neutrophil myeloperoxidase. Disease/Dx?

A

Eosinophilic granulomatosis with polyangiitis (Churg-Strauss)

Small vessel vasculitis with MPO-ANCA/p-ANCA +

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32
Q

People with narcolepsy lack what 2 neuropeptides?

A

Hypocretin-1 (Orexin-A)
Hypocretin-2 (Orexin-B)

These neuropeptides function to promote wakefulness and inhibit REM-sleep → thus without these you would be very sleepy

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33
Q

In addition to skin lesions, where else can Kaposi’s sarcoma (caused by HHV-8) manifest?

A

Lungs and GI tract (diarrhea)

Remember, KS is typically found in people with HIV

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34
Q

What is characteristic on histology of pancreatic beta cells in patients with Type 2 DM?

A

Islet amyloid polypeptide deposits

Type 1 DM has leukocytic infiltrate

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35
Q

What is the general pathogenesis of Paget disease of the bone?

A

Osteoclast dominant, increased bone resorption
↓
Osteoclast + Osteoblast activity, creation of disorganized, abnormal bone
↓
Osteoblast dominant, haphazard creation of bone with a mosaic pattern and prominent cement lines

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36
Q

In order of decreasing involvement, what vessels are most commonly involved in development of atherosclerotic plaques?

A

Abdominal aorta > coronary arteries > popliteal arteries > internal carotid arteries

Abdominal aorta is the most common/involved!

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37
Q

What are the structural components of MHC Class I and MHC Class II cell surface molecules and what type of cells do they present antigen to?

A

MHC Class I

  • heavy chain and B2-microglobulin
  • present to CD8+ (cytotoxic T cells)

MHC Class II

  • alpha and beta polypeptide chains
  • present to CD4+ (helper T cells)
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38
Q

What is the most important factor for determining cancer prognosis?

A

Stage - indicates extent of tumor expansion

Grade indicates tumor differentiation and is less important in prognosis

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39
Q

What are the four rotator cuff muscles and what are their physiologic functions on shoulder movement?

A

Supraspinatus m. → Abduction

Infraspinatus m. → External rotation

Teres minor m. → Adduction and external rotation

Subscapularis m. → Adduction and internal rotation

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40
Q

What is the key autoantibody, histologic characteristic and clinical finding of bullous pemphigoid?

A

Antibodies against hemidesmosomes

Histology → subepidermal cleavage causing separation of the epidermis from the dermis

Clinical → TENSE blisters (look like they are going to pop)

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41
Q

What is the key autoantibody, histologic characteristic and clinical finding of pemphigus vulgaris?

A

Antibodies against desmosomes

Histology → intraepithelial cleavage with acantholysis

Clinical → FLACCID blisters with oral/mucosal involvement

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42
Q

What is the most common cause of bacterial meningitis in adults of all ages?

A

Strep pneumoniae

2nd most common is Neisseria meningitidis

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43
Q

What is the child version of antisocial personality disorder?

A

Conduct disorder

Must be 18 years old

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44
Q

What is the characteristic murmur caused by a patent ductus arteriosus?

A

Continuous, machine-like murmur

occurs through both diastole and systole

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45
Q

What can occur in patients who receive a massive quantity of blood transfusion (5-6 liters) due to citrate, a substance added to stored blood?

A

Hypocalcemia

The citrate contained in stored blood can chelate serum calcium in the recipient of the blood → can lead to symptoms of hypocalcemia such as paresthesias

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46
Q

What renal complication can result from chronic hemolysis?

A

Hemosiderosis - iron deposition in the kidney

This can cause interfere with proximal tubule function and cause interstitial scarring and cortical infarcts

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47
Q

What is the most common cause of retinitis in an HIV+ patient?

A

CMV infection

treated with ganciclovir

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48
Q

Where are cysts commonly seen in autosomal dominant polycystic kidney disease?

A

Kidneys - causes kidney failure, hematuria, flank pain
Liver
“Brain” - cerebral aneurysms that may rupture

Doesn’t typically present until adult age 30s-50s

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49
Q

Which artery courses with the radial nerve down the posterior aspect of the humerus and can be co-injured in the event of a mid-shaft humerus fracture?

A

Deep brachial artery

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50
Q

What key vitamins/molecules are created by the normal bacterial flora in the small intestines?

A

Vitamin K and Folate

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51
Q

What is tardive dyskinesia?

A

A movement disorder typically caused by long-term treatment with antipsychotics for schizophrenia

It is characterized by repetitive, rhythmic, involuntary movements of the tongues, lips, face, trunk and hands/feet

Ex - facial grimacing, tongue movements, lip smacking, puckering

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52
Q

What is the mechanism of hemolysis seen in diseases such as hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura and DIC?

A

These diseases result in microangiopathic hemolytic anemia

This is caused by some type of process either damage to the endothelial layer of small blood vessels or widespread clotting, but in both cases it results in fibrin deposition and platelet aggregation in smaller vessels

As blood flows past these obstructions in small vessels, it is sliced up leading to intravascular hemolysis and characteristic schistocytes (‘helmet cells’)

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53
Q

What is the underlying defect causing ‘white’, hypopigmented spots on people with vitiligo?

A

Loss of epidermal melanocytes

causing a complete absence of melanin pigment

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54
Q

A 35 yo pregnant woman presents with pain and tingling in her first three digits on both hands. On physical exam she has thenar atrophy. What is the most likely diagnosis?

A

Carpal tunnel syndrome

Caused by compression of the MEDIAN NERVE within the carpal tunnel and often appears BILATERALLY

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55
Q

What enzymes require thiamine to function that are particularly problematic in chronic alcoholic patients?

A

Pyruvate dehydrogenase - Pyruvate → Acetyl CoA

a-Ketoglutarate - a-Ketoglutarate → Succinyl CoA

Alcoholics are classically deficient in thiamine (vitamin B1) which shuts down the TCA cycle and results in Wernicke encephalopathy

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56
Q

During a surgery on a newborn, tan fat-containing tissue is found around the kidneys and adrenal glands. What is the function of this tan colored fat?

A

Brown adipose tissue produces heat in newborns, preventing hypothermia

Its brown color is due to a high amount of mitochondria which utilize the ETC to produce HEAT instead of ATP

TLDR - in lieu of producing ATP, brown fat mitochondria produce heat

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57
Q

What is a nonlactose-fermenting, oxidase-positive, motile, gram-negative rod that causes otitis externa?

A

Pseudomonas aeruginosa

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58
Q

What two chronic conditions cause hyaline arteriolosclerosis in medium to small sized arteries (particularly in the kidney)?

A

Hypertension and Diabetes Mellitus (poorly controlled or untreated in both cases)

Hyaline deposition will stain pink with periodic acid-Schiff (PAS) stain

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59
Q

What two transporters allow for calcium efflux from cardiac myocytes, allowing for myocyte relaxation?

A

Na+/Ca2+-exchange pump

Sarcoplasmic reticulum Ca2+-ATPase pump (SERCA)

Calcium must be pumped out of the cytoplasm to allow for cardiac muscle relaxation

60
Q

What lab test should be ordered when finding a xanthoma on physical exam?

A

Serum lipids and blood glucose level

to investigate for hyperlipidemia, dyslipidemia and potential insulin resistance

61
Q

What vein can experience thrombosis/blood clot formation due to pancreatic inflammation?

A

Splenic vein

The splenic vein runs along the posterior surface of the pancreas and can develop a blood clot from pancreatic inflammation

62
Q

A baby presenting with bilateral spastic paresis, abnormal involuntary movements and significantly elevated arginine levels in plasma and CSF likely has a problem with what metabolic pathway?

A

Urea cycle

This pathway breaks down nitrogenous waste (ammonia) from protein metabolism and turns it into urea for excretion from the body in urine

63
Q

What acid-base disorder is typically seen at very high altitudes acutely?

A

Respiratory alkalosis (low PaCO2) with compensatory drop in HCO3- → caused by hypoxemia (low PaO2) and resulting hyperventilation

64
Q

What inheritance pattern is seen in glucose-6-phosphate dehydrogenase (G6PD) deficiency?

A

X-linked recessive

Males are affected, females are generally carriers

65
Q

Decreased renal tubular reabsorption of lysine, arginine, ornithineand cysteine may lead to what complciation?

A

Kidney stones

cystine kidney stones due to increased levels of cystine in the urine

66
Q

What is typically produced in the rough endoplasmic reticulum?

A

Secretory, lysosomal and integral membrane PROTEINS

67
Q

What is typically produced in the smooth endoplasmic reticulum?

A

Steroid and phospholipid synthesis

steroid producing cells in the adrenals, gonads and liver contain a well-developed smooth ER

68
Q

Findings of weakness on foot plantarflexion, foot inversion, toe flexion and sensory loss over the sole of the foot are characteristic of what nerve injury?

A

Tibial nerve injury

may occur due to deep puncture injury at the level of the popliteal fossa or knee surgery

69
Q

What is the mechanism of action of the drug anastrozole?

A

Aromatase inhibitor

(inhibits aromatization of androgens, inhibiting estrogen synthesis)

Used in treatment of ER-positive breast cancer in postmenopausal women

70
Q

Integrin is transmembrane adhesion protein that interacts with elements within the cell and outside the cell to hold a cell in place. What molecules does integrin bind to within the cell and outside the cell?

A

Outside cell - fibronectin, collagen, laminin

Inside cell - keratin, actin

71
Q

What drug is used to medically induce an asthmatic state in patients suspected of having asthma?

A

Methacholine

Methacholine is a muscarinic cholinergic agonist that induces bronchial smooth muscle contraction and bronchial mucus production

72
Q

What kind of bacteria can be found in the soil and survive boiling temperatures (212F/100C)?

A

Spore-forming bacteria

Clostridium and Bacillus species

73
Q

Where are two common locations for Burkitt lymphoma to appear?

A

Jaw lesion (endemic form in Africa)

Pelvis or abdomen in sporadic form

74
Q

What is the most common type of glomerulonephritis and frequently appears 3-7 days after an upper respiratory infection?

A

IgA nephropathy (Berger disease)

Painless, episodic, self-limited hematuria is frequently seen within 5 days of an upper respiratory tract infection

mesangial IgA deposits can be seen on immunohistochemical staining

75
Q

What is the venous drainage of internal and external hemorrhoids?

A

Internal (above pectinate) - superior rectal vein → inferior mesenteric vein → portal system

External (below pectinate) - inferior rectal vein → internal pudendal vein → internal iliac vein → common iliac vein → IVC

76
Q

What symptoms are typically caused by temporal arteritis (giant cell vasculitis)H?

A
  • Headache, typically in the temple region
  • Jaw pain while chewing
  • Polymyalgia rheumatica - neck, torso, pelvic pain
  • Sudden vision loss
77
Q

How many calories are yielded per gram of protein, carbohydrate and fat?

A

Protein - 4 Cal/g
Carbs - 4 Cal/g
Fat - 9 Cal/g

78
Q

What cellular organelles oxidase very long chain fatty acids and phytanic acids (branched chain fatty acids)?

A

Peroxisomes

Mitochondria CANNOT oxidase the very long chain fatty acids

79
Q

What are the key growth factors that stimulate angiogenesis?

A

Vascular endothelial growth factor (VEGF)

Fibroblast growth factor (FGF)

80
Q

How is the A-a gradient calculated?

A

PAO2 - PaO2 = A-a gradient

PAO2 (O2 in alveoli) = 150 - ( PaCO2 / 0.8)

PaO2 (O2 in arteries) = arterial blood gas measure

81
Q

What are the four morphologic stages of lobar pneumonia?

A

Congestion - red lobe, dilated alveoli, bacterial exudate

Red hepatization - red lobe, exudate contains RBCs, neutrophils, fibrin

Gray hepatization - pale, gray lobe, exudate only contains alveoli and fibrin

Resolution - restoration of normal lung architecture

82
Q

What amino acid cannot be made and is thus essential in phenylketonuria?

A

Tyrosine

presents with intellectual disability, seizures, light pigmentation of skin/hair, and a musty odor

83
Q

What causes pleuritic chest pain and low-grade fever 2-4 days following a transmural myocardial infarction?

A

Early-onset pericarditis can develop in 10-20% of people

This is caused by an inflammatory reaction to cardiac muscle necrosis that occurs in the adjacent visceral and parietal pericardium

(late-onset pericarditis weeks to months after MI is due to autoimmune-mediated Dressler syndrome)

84
Q

Fracture of the femoral neck (common in elderly fall scenarios) may be complicated by osteonecrosis caused by injury to what artery?

A

Medial femoral circumflex artery

This artery provides the majority of the blood supply to the femoral neck and head

85
Q

What pancreatic secretion is stimulated by secretin?

A

HCO3-

Secretin is released in response to increased H+ (gastric acid) in the duodenum

86
Q

What two types of cancers are strongly associated with human papillomavirus and what types of HPV?

A

Cervical squamous cell carcinoma (women)

Anal squamous cell carcinoma (men, particularly w/ HIV)

HPV 16 and 18 are high risk strains

87
Q

What extraintestinal manifestations occur in Crohn disease as a result of impaired absorption in the small intestines?

A

Macrocytic anemia → B12 and folate deficiency

Kidney stones → calcium loss in feces bound to fat (↑ oxalate absorption leading to stones)

Gallstones → decreased bile acid reabsorption in the terminal ileum

88
Q

What vitamin supplementation can reduce cormorbidities in patients with measles (ocular complications, diarrhea and pneumonia)?

A

Vitamin A

Esp. reduces ocular complications of measles (remember Vitamin A is like the eye health vitamin)

89
Q

What class of drug is glyburide and what is its mechanism of action?

A

Sulfonylurea

Sulfonylureas increase endogenous insulin secretion by binding to and closing the K+ channel in pancreatic beta cell membranes → causes cell depolarization → insulin release via ↑ Ca2+ influx

90
Q

What is the name of the dopaminergic pathway that controls prolactin secretion?

A

Tuberoinfundibular pathway

(antipsychotic drugs can block dopamine in this pathway, resulting in increased prolactin secretion and subsequent galactorrhea)

91
Q

What is the name of the dopaminergic pathway that regulates behavior?

A

Mesolimbic-mesocortical pathway

this is the pathway targeted for dopamine block by antipsychotic medications to treat schizophrenia

92
Q

What is the name of the dopaminergic pathway that regulates coordination of voluntary movement?

A

Nigrostriatal pathway

reduced dopamine in this pathway is responsible for Parkinsonism

93
Q

What is hibernating myocardium?

A

This refers to changes due to chronic myocardial ischemia due to reduced coronary blood flow (perhaps due to a stenosis)

It results in decreased contractility and left ventricular systolic dysfunction as the heart adapts to the lower oxygen delivery, attempting to self-preserve the myocardium

These changes are REVERSIBLE by improving the coronary blood flow (through surgical or other means)

94
Q

Asplenic patients have increased susceptibility to what bacteria and what type of infection?

A

↑ susceptibility to encapsulated organisms such as Strep pneumoniae, N. meningitidis and H. influenzae

These infections result in bacteremia and sepsis because the spleen acts as a blood filter capable of removing circulating pathogens and stimulating opsonizing antibody synthesis

95
Q

A patient presenting with frequent self-limited, colicky abdominal pain, facial swelling and lab workup indicating complement protein C1 excessively cleaving C2 and C4 likely has what disorder?

A

C1 inhibitor deficiency

(inhibitor deficiency meaning there is thus too much C1 around cleaving shit)

Buildup of bradykinin because of increased C1 cleaving activity causes the angioedema

96
Q

Sucrose is a disaccharide composed of what two monosaccharides?

A

Sucrose = Fructose + Glucose

People with hereditary fructose intolerance (Aldolase B deficiency → toxic accumulation of fructose 1-phosphate) should avoid sucrose and fructose

97
Q

What is the rate-limiting step in fatty acid synthesis?

A

Conversion of acetyl-CoA to malonyl-CoA via the enzyme Acetyl-CoA carboxylase (occurs in the cytoplasm)

98
Q

What molecule inhibits mitochondrial carnitine acyltransferase (carnitine shuttle), thereby inhibiting beta-oxidation of fatty acids?

A

Malonyl-CoA

Because malonyl-CoA is used in the synthesis of fatty acids (indicating an anabolic state), its presence in high concentrations inhibits the breakdown of fatty acids (a catabolic function)

99
Q

What is the major rate-limiting step in glycolysis?

A

Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate by phosphofructokinase-1

100
Q

What is the function of the c-Myc oncogene?

A

c-Myc functions as a transcription activator controlling cell proliferation, differentiation and apoptosis

It is overactive in Burkitt lymphoma; t(8:14)

101
Q

Myocardial infarction with ST elevations in leads II, III and aVF would indicate occlusion of which coronary artery?

A

Right coronary artery

II, III, aVF indicate an infarction on the inferior aspect of the heart

102
Q

Myocardial infarction with ST elevations in leads V1-V4 would indicate occlusion of which coronary artery?

A

Left anterior descending

V1-V4 indicate infarction on the anteroseptal aspect of the heart

103
Q

Myocardial infarction with ST elevations in leads V5 and V6 (and possibly I and aVL) would indicate occlusion of which coronary artery?

A

Left circumflex artery

V5-V6 indicate infarction on the lateral wall of the left ventricle

104
Q

What is a lactose-fermenting, indole-positive gram-negative rod?

A

E. coli

Indole-positivity helps distinguish E. coli from Enterobacter cloacae, another gram-negative lactose-fermenting rods that commonly causes UTI

105
Q

Where in the ear does hearing loss due to chronic exposure to loud noises occur?

A

Organ of corti → damage is specifically done to the stereociliated hair cells within the organ of corti

106
Q

Compared to healthy individuals, people with cystic fibrosis will have high concentrations of what in their sweat?

A

Cholride and sodium

Normally, cholride is resorbed via CFTR with sodium following as isotonic eccrine sweat moves through the eccrine ducts to the skin surface (making hypotonic sweat)

→ this resorption doesn’t occur in CF patients due to absent CFTR and so cholride and sodium are lost in the sweat

107
Q

What muscle travels through the greater sciatic foramen? lesser sciatic foramen?

A

Piriformis m. travels through greater sciatic foramen (along with the sciatic nerve)

Obturator internus m. travels through the lesser sciatic foramen

108
Q

What component of gram-negative bacteria (such as E. coli) is responsible for causing septic shock?

A

Lipid A, a component of lipopolysaccharide (LPS) in gram-negative bacterial cell walls

LPS (and thus Lipid A) is released from bacterial cells during division or bacteriolysis

Lipid A causes activation of macrophages leading to release of IL-1 and TNF-a which primarily cause the signs/symptoms of septic shock

109
Q

What is peripheral venous capacitance?

A

The amount of blood volume that can be held in the peripheral veins at a given point in time

Venodilators (nitrates) would thus increase peripheral venous capacitance by widening the vessels, allow for greater volume

Vasoconstrictors would decrease venous capacitance

110
Q

What are possible paraneoplastic syndromes of small cell carcinoma?

A

ACTH secretion by tumor (causing Cushing syndrome)

ADH secretion by tumor (causing SIADH)

Eaton-Lambert syndrome (blocks ACh release at NMJ)

111
Q

What are possible paraneoplastic syndromes of squamous cell carcinoma?

A

PTHrP secretion by tumor (causing hyperparathyroidism-like symptoms → ↑ serum Ca2+, bone pain etc.)

112
Q

What is the most common malignant neoplasm of the liver?

A

Metastasis from another primary source (breast, lung, colon)

Metastatic cancer in the liver typically appears as multiple nodules throughout the liver

113
Q

Pelvic floor weakening resulting in stress urinary incontinence is caused by weakening/injury of what muscle?

A

Levator ani muscle

Kegel exercises are pelvic floor strengthening exercises which may treat or improve stress urinary incontinence

114
Q

By what mechanism do the two different agents lactulose and rifaximin treat hepatic encephalopathy?

A

Hepatic encephalopathy is caused by accumulation of ammonia in the brain

Lactulose → increases conversion of ammonia to non-toxic ammonium (NH4+ can’t be absorbed)

Rifaximin → decreases intraluminal ammonia production by antibiotic action, altering GI flora

115
Q

What cardiac abnormality is associated with DiGeorge syndrome (trisomy 18)?

A

Tetralogy of Fallot

116
Q

What cardiac abnormality is associated with Friedreich’s ataxia (GAA trinucelotide repeat on frataxin gene)?

A

Hypertrophic cardiomyopathy

117
Q

What cardiac abnormality is associated with tuberous sclerosis?

A

Valvular obstruction due to cardiac rhabdomyomas

118
Q

What cardiac abnormality is associated with Down syndrome?

A

Atrial septal defects (endocardial cushion defects)

119
Q

A 40 y/o woman presents with a 6-month history of episodic bouts of ‘spinning sensation” associated with nausea, ringing and difficulty hearing in her left ear. Between these episodes, she doesn’t experience any of these symptoms. Disease/Dx?

A

Meniere disease - a disorder of the inner ear

Caused by increased volume and pressure of endolymph in the inner ear

Causes recurrent, episodic vertigo (dizziness), ear pain and hearing loss/tinnitus

120
Q

What type of kidney injury is most commonly caused by chronic use of NSAIDs?

A

Chronic interstitial nephritis

This causes fibrosis, tubular atrophy and can lead to papillary necrosis and scarring

121
Q

What tumors are associated with familial retinoblastoma?

A

Retinoblastoma (ocular neoplasm, duh)

Osteosarcoma (bone tumor of the metaphysis)

122
Q

What is the mechanism of action of the drugs amiloride and triamterene?

A

Block the epithelial sodium channel (ENaC) in the collecting duct of the renal tubules, inhibiting sodium reabsorption

These are K+ sparing diuretics and can cause hyperkalemia

123
Q

A 23 yo male presents with weakness and gait disturbance. He indicates he has difficulty releasing doorknobs after use. Physical exam shows cataracts, frontal baldness and gonadal atrophy. Disease/Dx?

A

Myotonic dystrophy

Autosomal dominant trinucleotide (CTG) repeat disease of the DMPK gene

Causes abnormal expression of myotonin protein kinase

124
Q

A deep, bleeding ulcer on the posterior wall of the duodenal bulb has likely penetrated which artery?

A

Gastroduodenal artery

The gastroduodenal artery perfuses both the pylorus of the stomach and the proximal part of the duodenum

(the duodenal bulb is the very first part of the duodenum that the stomach empties into)

125
Q

What is coronary steal?

A

A phenomenon in coronary vessels in which blood flow to ischemic areas is reduced due to arteriolar vasodilation in nonischemic areas

Drugs such as adenosine and dipyridamole can cause coronary steal due to their selective vasodilatation of coronary vessels

126
Q

What is the role of the NF-kB pathway in the immune system?

A

NF-kB is a proinflammatory transcription factor that increases cytokine production

127
Q

What is a common adverse effect of the cancer drug vincristine?

A

Neurotoxicity - commonly manifests as peripheral neuropathy

Vincristine (vinca alkaloid) inhibits microtubule formation, preventing cell division (in M phase of cell cycle)

128
Q

What three drugs most commonly cause drug-induced lupus erythematosus?

A

Hydralazine (arteriolar vasodilator)
Procainamide (class Ia antiarrhythmic)
Isoniazid

Typically occurs in people who are “slow acetylators”
Anti-histone and anti-nuclear antibodies may be seen on labs

129
Q

A patient’s ECG shows absent P waves, irregularly irregular R-R intervals and narrow QRS complexes. What cardiac abnormality is present?

A

Atrial fibrillation

Caused by heightened atrial excitability, AV nodal refractory period prevents a corresponding ventricular arrhythmia

130
Q

A 27 y/o woman presents with a 1-day history of rash that began approximately 2 weeks after an episode of recurrent, painful genital lesions. The rash appears as many red, round papules with some evolving into target lesions. Disease/Dx?

A

Erythema multiforme

Cell-mediated inflammatory disorder of the skin commonly associated with HERPES SIMPLEX VIRUS

131
Q

What distinguishing lab findings would help differentiate von Willebrand disease from immune thrombocytopenic purpura?

A

Platelet count would be NORMAL in von Willebrand disease (it is a qualitative disorder, also ↓ aPTT)

Platelet count would be DECREASED in thrombocytopenic purpura because of autoimmune destruction of platelets

Both would present with recurrent nosebleeds (epistaxis), easy bruising, petechiae and mucosal bleeding

132
Q

What is the suspected origin of small cell carcinoma?

A

Neuroendocrine origin

This is why small cell carcinoma typically stains for neuroendocrine markers such as CHROMOGRANIN, neural cell adhesion molecules and enolase

May also tie in to its ADH/ACTH secretion and Lambert-Eaton syndrome

133
Q

Where doe the patellar ligament attach to the lower leg?

A

Tibial tuberosity

Quadriceps muscle group attaches to the patella and the patella attaches to the tibial tuberosity → this allows for leg extension at the knee

134
Q

What are common adverse effects of dihydropyridine calcium channel blockers (amlodipine, nifedipine)?

A

Dizziness or lightheadedness

PERIPHERAL EDEMA

135
Q

What cytokine mediates cachexia (anorexia, malaise, weight loss, generalized wasting) in patients with cancer?

A

TNF-alpha

TNF-a is thought to mediate paraneoplastic cachexia by suppressing appetite and increasing basal metabolic rate

136
Q

What hormone does high levels of prolactin suppress?

A

GnRH → this leads to ↓ LH/FSH and ↓ estrogen/testosterone

137
Q

What type of cellular injury is seen in reperfusion injury?

A

Reperfusion injury occurs after blood flow is resumed in tissue recovering from ischemic damage

It causes cellular damage by oxygen free radical generation, mitochondrial damage and inflammation

138
Q

What are the acute effects of corticosteroid use on white blood cell count?

A

↑ neutrophil count (temporarily, due to ‘demargination’of neutrophils previously attached to vessel walls)

↓ basophils, eosinophils, monocyte/macrophage, lymphocytes

139
Q

What causes the accumulation of lipid cells in alcohol-induced hepatic steatosis?

A

Decreased free fatty acid oxidation (↓ fatty acid breakdown)

Thought to occur due to excess NADH production by the two major alcohol metabolism enzymes; alcohol dehydrogenase and aldehyde dehydrogenase

140
Q

What are the two most common causes of acute respiratory distress syndrome (ARDS)?

A

Sepsis and pneumonia

In both scenarios, cytokines circulating in response to infection ultimately cause leakage of protein and fluid into the alveolar space

141
Q

What main structures are compressed by a transtentorial (uncal) herniation?

A

Oculomotor nerve (CN III) and sometimes posterior cerebral artery (causing vision disturbance)

142
Q

What main structures are compressed by a subfalcine herniation?

A

Anterior cerebral artery (causing infarction)

143
Q

What main structures are compressed by a tonsillar herniation?

A

Medulla/brainstem (causing cardiopulmonary arrest)

144
Q

Selective COX-2 inhibitors (celecoxib) have a different side effect profile than NSAIDs and asipirin. What adverse effects are blunted/absent with selective COX-2 inhibitor use?

A

Lower risk of bleeding and gastric ulceration

The lower risk of bleeding results from inhibition of prostacyclin (PGI2) inhibition of platelet aggregation which can actually INCREASE risk of cardiovascular events (↑ platelet aggregation)

145
Q

A patient presents with signs and symptoms of chronic hemolytic anemia. Their red blood cells demonstrate increased fragility in an acidified glycerol lysis test. Disease/Dx?

A

Hereditary spherocytosis
(spectrin/ankyrin mutations causing red cell cytoskeleton abnormalities)

A positive acidified glycerol lysis test is diagnostic for hereditary spherocytosis
→ increased osmotic fragility is due to decreased surface area to volume ratio

USMLE Step 1 (7 decks)

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