Uworld27

Question 1

Function of parietal cells

Answer 1

Parietal cells release hydrogen ions into the gastric lumen by means of the H/K ATPase, which requires hydrolysis of ATP and is therefore an active transport mechanism.

Omeprazole and other proton pump inhibitors suppress the activity of the gastric parietal cell H/K ATPase leading to an increase in the pH of the gastric lumen.

Question 2

To access the left side of the heart, cardiac venous catheters must cross?

Answer 2

the interatrial septum at the site of the foramen ovale.

Entry into the left atrium allows for direct measurement of left atrial pressure and for access to arrhythmogenic foci on the left atrial myocardium or pulmonary veins.

Question 3

Neisseria can be isolated on which medium?

Answer 3

Neisseria can be isolated by culture on selective media such as the Thayer-Martin VCN (vancomycin/colistin/nystatin) medium, which inhibits growth of contaminants such as gram+ organisms, gram negative organisms other than Neisseria, and fungi.

Question 4

What is septic shock?

Answer 4

Septic shock is a dysfunctional host response to an infectious pathogen resulting from massive upregulation of vasodilators.

A vasopressin deficit contributes to unbalanced vasodilation and refractory hypotension.

Question 5

Hepatic A virus infection is characterized by?

Answer 5

Hepatitis A virus infection is most commonly silent or subclinical (“anicteric”) in young children but can also present as an acute, self limited illness characterized by jaundice, malaise, fatigue, anorexia, nausea, vomiting, RUQ pain, or an aversion to smoking.

Question 6

What is a migraine?

Answer 6

an episodic neurologic disorder that results in severe, unilateral, throbbing headaches that are often associated with photophobia, phonophobia, and nausea/vomiting.

Migraine attacks typically last 4-72 hours, and up to 25% of patients also develop an aura (focal, reversible neurologic symptoms that precede or accompany the headache)

Question 7

What is infantile hemangiomas?

Answer 7

benign vascular tumors composed of proliferating endothelial cells that most frequently affect the head or neck region.

Natural history of these lesions involve rapid growth of a red, cutaneous plaque followed by spontaneous regression.

Question 8

What is schizophrenia?

Answer 8

diagnosed in patients with signs of disturbance for >6 months, including at least 1 month of >2 of the following active symptoms (with at least 1 from the first 3): delusions, hallucinations, disorganized speech, disorganized/catatonic behavior, and negative symptoms.

Question 9

Treatment of acromegaly

Answer 9

Acromegaly is usually treated with resection of the somatotroph pituitary adenoma, but additional medical therapy is needed for patients with residual tumor.

Octreotide is a long acting somatostatin analogue that inhibits growth hormone secretion and subsequently insulin-like growth factor-1 release. It also reduces residual adenoma size in many patients.

Question 10

What is the most common etiology of mesial temporal lobe epilepsy?

Answer 10

Recurrent focal impaired awareness seizures that are preceded by a distinctive aura (eg, uneasy epigastric sensation, olfactory hallucinations) are characteristic of mesial temporal lobe epilepsy.

The most common etiology is hippocampal sclerosis (mesial temporal sclerosis), which is associated with childhood febrile seizures.

Question 11

Formula for absolute risk reduction

Answer 11

Absolute risk reduction = event rate in the control group - event rate in the treatment group

Question 12

MOA of aromatase inhibitors (anastrozole, letrozole, exemestane)

Answer 12

Estrogen is the main hormone responsible for the growth and development of estrogen receptor-positive breast tumors.

Aromatase inhibitors decrease the synthesis of estrogen from androgens, suppressing estrogen levels and slowing progression of ER+ tumors.

Question 13

t-test is used to compare?

Answer 13

the difference between the means of 2 groups.

Question 14

Analysis of variance (ANOVA) compares?

Answer 14

the difference between the means of 2 or more groups.

Question 15

What is McCune-Albright syndrome?

Answer 15

characterized by the triad of fibrous dysplasia of the bone, endocrine abnormalities, and cafe-au-lait spots.

The condition results from an activating mutation in the G protein/cAMP/adenylate cyclase signaling pathway.

Question 16

What is acute respiratory distress syndrome?

Answer 16

characterized by hypoxia and bilateral pulmonary infiltrates and is associated with pneumonia, sepsis, trauma, and pancreatitis.

The associated pulmonary edema is noncardiogenic in nature, so the pulmonary capillary wedge pressure will be within the normal range (6-12 mmHg)

Question 17

What is the mutations seen in adenocarcinoma of the lung?

Answer 17

the most common primary lung cancer in the general population, women, and nonsmokers.

Epidermal growth factor receptor (EGFR) mutations and ALK gene rearrangments are seen more commonly in nonsmokers and thought to contribute to disease formation in this subgroup.

Adenocarcinoma is typically located peripherally and may be associated with clubbing or hypertrophic osteoathropathy.

Question 18

What is occupational asthma?

Answer 18

involves airway inflammation and bronchoconstriction triggered by sensitization to a workplace aeroallergen (eg, isocyanates, grain proteins).

Improvement on sustained absence from work (eg, vacation) is an important clinical clue.

Normal spirometry does not exclude asthma because bronchospasm may occur intermittently.

Question 19

What is linkage disequilibrium?

Answer 19

Two allele loci are said to be in linkage disequilibrium when a pair of alleles are inherited together in the same gamete (haplotype) more often or less often than would be expected given random pairing.

This most often occurs when the genes are in close physical proximity on the same chromosome.

Question 20

What is acute interstitial nephritis?

Answer 20

a common cause of renal dysfunction; up to 75% of cases are due to medications including nonsteroidal anti-inflammatory drugs, antibiotics, diuretics, and proton pump inhibitors.

Presenting features include fever, rash, and eosinophilia.

UA: pyuria and WBC casts with elevated urine eosinophils.

Question 21

What is sarcoidosis?

Answer 21

an inflammatory disorder characterized histologically by noncaseating granulomas consisting of aggregates of epithelioid macrophages and multinucleated giant cells.

Common manifestations include hilar adenopathy, pulmonary infiltrates, skin rash, ophthalmic findings, and constitutional symptoms.

Question 22

What is recall bias?

Answer 22

results from study participants’ inaccurate recall of past exposure and occurs most often in retrospective studies such as case-control studies.

People who have experienced an adverse effect are more likely to recall risk factors than those who have not experienced an adverse event.

Question 23

Hyperprolactinemia suppresses secretion of?

Answer 23

GnRH, which leads to reduced estrogen in women. Low estrogen levels are a risk factor for accelerated bone loss.

Question 24

What is pseudocholinesterase deficiency?

Answer 24

Succinylcholine, a depolarizing neuromuscular blocking agent, is rapidly hydrolyzed by plasma pseudocholinesterase.

Patients with pseudocholinesterase deficiency have prolonged neuromuscular paralysis after drug adminstration.

Question 25

What is HIV-associated dementia?

Answer 25

HIV-associated dementia should be suspected in patients with AIDS who have progressive cognitive decline. The characteristic histopathologic finding is microglial nodules (groups of activated microglia/macrophages around small areas of necrosis) and multinucleated giant cells.

Question 26

What is injured in a supracondylar humeral fracture?

Answer 26

Supracondylar humeral fractures commonly occur after hyperextension of the elbow as a result of a fall onto an outstretched arm. The median nerve and brachial artery run along the anteromedial aspect of the elbow and are the structures most likely to be injured with anteromedial displacement of the proximal fracture fragment.

Question 27

Carotid sinus massage leads to?

Answer 27

an increase in parasympathetic tone causing temporary inhibition of sinoatrial node activity, slowing of conduction through the atrioventricular node, and prolongation of the AV node refractory period. It is a useful vagal maneuver for termination of paroxysmal supraventricular tachycardia.

Question 28

What causes head lice?

Answer 28

Pediculus human capitis (ie, head lice) infestation is common in school children and adults who come into close contact with infested individuals. Transmission is usually by direct contact. The eggs (nits) are attached to the hair shaft and can be identified on inspection. First line treatment includes topical pediculicides (eg, permethrin, ivermectin)

Question 29

MOA of bile acid-binding resins (eg, cholestyramine, colestipol, colesevelam)

Answer 29

inhibit the enterohepatic circulation of bile acids. This leads to diversion of hepatic cholesterol to synthesis of new bile acids, increased uptake of cholesterol from the circulation, and reduced blood LDL levels. However, bile acid binding resins increase hepatic production of triglycerides and can cause hypertriglyceridemia.

Question 30

What is mitral stenosis?

Answer 30

opening snap followed by a rumbling diastolic murmur that is best heard over the cardiac apex. On the left ventricular pressure-volume loop, the opening snap occurs during mitral valve opening at the end of isovolumetric relaxation, and it is followed by a diastolic rumble during diastolic filling.

Question 31

What is selection bias?

Answer 31

In prospective studies, disproportionate loss to follow up between the exposed and unexposed groups creates the potential for attrition bias, which is a form of selection bias. As a result, investigators generally try to achieve high patient follow-up rates in prospective studies.

Question 32

What is the Golgi tendon system?

Answer 32

The muscle spindle system is a feedback system that monitors and maintains muscle length, while the Golgi tendon system is a feedback system that monitors and maintains muscle force. Golgi tendon organs are exquisitely sensitive to increases in muscle tension but are relatively insensitive to passive stretch.

Question 33

The internal larygneal nerve mediates?

Answer 33

the afferent limb of the cough reflex above the vocal cords. Foreign bodies (eg, fish bones) can become lodged in the piriform recess and may cause damage to the nerve, impairing the cough reflex.

Question 34

In chronic kidney disease, reduced excretion of phosphate can cause hyperphosphatemia. This induces?

Answer 34

hypocalcemia directly by binding free calcium and depositing in tissues, and indirectly by triggering fibroblast growth factor 23 secretion (decreases calcitriol production and intestinal calcium absorption). The resulting hypocalcemia can manifest as neuromuscular excitability (eg, carpal spasm)

Question 35

MOA of topical capsaicin

Answer 35

causes defunctionalization of afferent pain fibers and depletion of substance P. Initial application results in a burning stinging sensation, but chronic exposure leads to reduced pain transmission.

Question 36

What is Pott disease?

Answer 36

Mycobacterium tuberculosis spondylitis (Pott disease) is usually the result of hematogenous seeding of vertebrae from primary pulmonary infection. Manifestations typically arise months or years later (due to reactivation) and include chronic, progressive back pain, fever, and radiographic evidence of vertebral bone destruction and fluid collection.

Question 37

What are the most common adverse effects of psychostimulant meds used to treat attention-deficit hyperactivity disorder?

Answer 37

decreased appetite and insomnia. They are usually mild and can be managed without stopping the medication.

Question 38

What is hirschsprung disease?

Answer 38

a congenital disorder caused by failure of normal craniocaudal migration of neural crest cells during embryogenesis. The affected colon segment (eg, rectosigmoid) lacks ganglionic innervation and is unable to relax, resulting in obstruction with failure to pass meconium and bilious emesis. Forceful expulsion of gas and stool on rectal exam is typical.

Question 39

Acetylcholine release from presynaptic terminal vesicles at the neuromuscular junction depends upon?

Answer 39

the influx of extracellular calcium into the presynaptic terminal. Calcium influx into the nerve terminal occurs following neuronal depolarization and opening of voltage gated calcium channels.

Question 40

What is septic abortion?

Answer 40

Symptoms of septic abortion typically include fever, abdominal pain, uterine tenderness, and/or malodorous discharge after pregnancy termination. Common pathogens include Enterobacteriaceae, group A strep, and Staph aureus. Treatment: urgent surgical evacuation and broad spectrum antibiotics.

Question 41

What is C1 inhibitor (C1INH) deficiency?

Answer 41

C1INH deficiency causes increased cleavage of C2 and C4 and results in inappropriate activation of the complement cascade. C1INH also blocks kallikrein-induced conversion of kininogen to bradykinin, a potent vasodilator associated with angioedema.

Question 42

MOA of ACE inhibitors?

Answer 42

ACE inhibitors reduce angiotensin II levels and cause efferent arteriole dilation, thereby decreasing the glomerular filtration pressure and filtration rate. This can precipitate acute renal failure in patients with reduced intrarenal perfusion pressure at baseline (eg, renal artery stenosis, congestive heart failure, hypovolemia)

Question 43

Pathogenesis of Mycobacterium tuberculosis infection

Answer 43

Th1 cells release interferon-gamma, leading to the activation of macrophages, a process critical for control of Mycobacterium tuberculosis infection. Activated macrophages form mature phagolysosomes that destroy phagocytosed mycobacteria and can differentiate into epithelioid and Langhans giant cells to wall off extracellular mycobacteria within caseating granulomas.

Question 44

Function of vitamin C

Answer 44

cofactor for the hydroxylation of proline and lysine during collagen synthesis, which is essential for maximum tensile strength. Def (scurvy) is charactered by periodontal disease, impaired wound healing, vascular wall fragility (eg, perifollicular, subperiosteal hemorrhage), follicular hyperkeratosis, and corkscrew hairs.

Question 45

Function of hydroxyurea

Answer 45

Hydroxyurea increases fetal hemoglobin production, which reduces erythrocyte sickling in patients with sickle cell disease. It also inhibits ribonucleoside reductase, which decreases deoxynucleoside triphosphates available for DNA synthesis; this leads to macrocytosis and with high doses, pancytopenia

Question 46

Following endothelial damage, von Willebrand factor binds to?

Answer 46

glycoprotein Ib receptors on platelets to mediate platelet adherence. The ristocetin cofactor assay measures platelet agglutination via binding of glycoprotein Ib receptors to vWF; it will be abnormal in vWF def but will correct with the addition of normal (vWF-containing) plasma.

Question 47

Def of vitamin B12

Answer 47

B12 is an essential cofactor in the recycling of 5-methyl-tetrahydrofolate, which is required for amino acid, purine, and thymidine synthesis. Def primarily affects hematopoiesis and is marked by impaired nuclear maturation, leading to macrocytic red blood cells and hypersegmented neutrophils; increased apoptosis often also leads to anemia and mild thrombocytopenia/leukopenia.

Question 48

Activating mutations of the KRAS gene lead to constitutive activation of?

Answer 48

epidermal growth factor receptor (EGFR) pathway, promoting increased cell proliferation and growth. Tumors harboring these mutations are resistant to treatment with anti-EGFR drugs (eg cetuximab, panitumumab)

Question 49

What is aortic stenosis most commonly results from?

Answer 49

from age-related calcific aortic valve disease. The early pathogenesis closely mimics that of arterial atherosclerosis. In the later stages, fibroblasts differentiate into osteoblast-like cells and deposit bone matrix, leading to progressive valvular calcification and stenosis.

Question 50

What are the difference between long acting insulin analogues (eg, glargine) and rapid acting insulins (eg, aspart, lispro)?

Answer 50

Long-acting insulin analogues (eg, glargine) have an extended duration of action without a noticeable peak in activity and are typically given once daily to mimic basal insulin secretion. Rapid-acting insulins (eg, aspart, lispro) are quickly absorbed from the injection site and are given at mealtimes to replicate postprandial insulin secretion.

Question 51

What are hepatocellular adenomas?

Answer 51

benign liver tumors found predominantly in young women with a history of oral contraceptive use. They are usually solitary, unencapsulated masses composed of benign hepatocytes and prominent arteries without normal portal tracts. Patients may be asymptomatic, have abdominal pain, or have intrabdominal bleeding due to tumor rupture.

Question 52

Bartonella henselae causes?

Answer 52

cat scratch disease, bacillary angiomatosis, and culture negative endocarditis. Cat scratch disease: low fever, lymphadenopathy, and a self limited course.

Question 53

What is the blood supply of the esophagus?

Answer 53

Forceful retching can lead to superficial mucosal lacerations (eg, Mallory-Weiss tears) of the distal esphagus, an area that receives most of its arterial blood supply from branches of the left gastric artery. proximal esophagus: inferior thyroid artery mid esophagus: branches of the thoracic aorta.

Question 54

What type of tumor is a teratoma?

Answer 54

Teratomas contain differentiated tissues from each of the 3 primary germ cell layers and are a type of germ cell tumor. Germ cell tumors originate from primordial germ cells and most commonly arise within the gonad itself (eg, ovarian germ cell tumor)

Question 55

What drug properties help the liver eliminate drugs?

Answer 55

While the kidney is the primary site of elimination of most drugs, the liver is the main site of biotransformation of these agents in preparation for elimination. Drugs that are more lipophilic (high Vd, good penetration into CNS) are preferentially processed by the liver into more polar compounds for easier elimination in the bile and urine. Liver disease (eg, cirrhosis) or the concomitant use of other drugs may limit or enhance the clearance of drugs metabolized in the liver.

Question 56

What is methylmalonic acidemia?

Answer 56

an organic acidemia/aciduria in newborns caused by deficiency of methylmalonyl-CoA mutase. Labs: elevated propionic acid, hypoglycemia, metabolic acidosis (ketone-mediated), and hyperammonemia.

Question 57

What test should be used for screening for life-threatening diseases?

Answer 57

The sensitivity of a test refers to its ability to correctly identify those with the disease. A highly sensitive test should always be considered over a high specific test when screening for life threatening diseases, where identification of every person with the disease is important.

Question 58

Melanoma has what kind of mutation?

Answer 58

BRAF is a protein kinase involved in activation of signaling pathways for melanocyte proliferation; the BRAF V600E mutation is seen in 40-60% of patients with melanoma.

Question 59

What are the physiologic responses to maintain adequate O2 delivery to the tissues in the hypoxic environment of high altitude?

Answer 59

hypoxic pulmonary vasoconstriction (increased pulmonary vascular resistance), increased sympathetic activity to increase cardiac output, and aldosterone suppression to reduce plasma volume.

Question 60

What is eosinophilic meningitis?

Answer 60

most often due to helminth infection (eg, Angiostrongylus). Peripheral eosinophilia is largely mediated by the release of IL-5 in response to helminths, allergens, drugs or rheumatic disease.

Question 61

Occlusion of the middle cerebral artery results in?

Answer 61

contralateral hemiparesis and hemisensory loss of the face and upper limb with relative preservation of lower limb function. If the occluded MCA is in the dominant (usually left) hemisphere, aphasia may also occur.

Question 62

function of b-hCG

Answer 62

b-hCG is a hormone secreted by the placental syncytiotrophoblast after uterine invasion that signals the ovary to maintain the corpus luteum, which produces progesterone in early pregnancy.

Question 63

MOA of vaptans (eg, tolvaptan)

Answer 63

Vaptans (eg, tolvaptan) are vasopressin V2 receptor antagonists (ie, aquaretics) used to treat hyponatremia. Vaptans block the effects of antidiuretic hormone (vasopressin), increasing renal free water excretion without directly affecting excretion of sodium or potassium. Diuresis of free water with vaptans results in increased plasma osmolality, increased serum sodium, increased urine output, and lowered urine osmolality.

Question 64

Paraneoplastic syndromes can occur due to?

Answer 64

the production of hormone like substances from tumor cells. They can also result from immune reactions against tumor cells that cross-react with normal cells, causing dysfunction and/or damage to healthy organs and tissues. Neurologic paraneoplastic syndromes (eg, paraneoplastic cerebellar degeneration) are an autoimmune phenomenon.

Question 65

Function of B6 pyroxidine

Answer 65

Transamination reactions typically occur between an amino acid and an a-keto acid. The amino group from the amino acid is transferred to the a-keto acid, and the a-keto acid in turn becomes an amino acid. Pyridoxal phosphate (active vitamin B6) serves as a cofactor in amino acid transamination and decarboxylation reactions.

Question 66

What is a prolactinoma?

Answer 66

Prolactinomas are the most common pituitary adenoma and can cause galactorrhea, menstrual irregularities, and infertility in premenopausal women. Large pituitary adenomas can cause headaches from mass effect and bitemporal hemianopsia from compression of the optic chiasm.

Question 67

What are the cardiac changes in pregnancy?

Answer 67

During pregnancy, systemic vascular resistance decreases and plasma blood volume increases. Venous capacitance and a decrease in pulmonary vascular resistance allow for accomodation of increased blood volume without affecting central venous pressure. Despite a normal central venous pressure, peripheral edema is common in pregnancy due to decreased capillary oncotic pressure that encourages leakage of fluid into dependent peripheral tissues (eg, lower extremities)

Question 68

Meningiomas arise from?

Answer 68

the meningothelial cells of the arachoid. Therefore, when they form in the spinal cord, they are located within the meninges in the intradural extramedullary space.

Question 69

What does HBeAg signify?

Answer 69

Infants born to HBeAg+ mothers have a high risk for acquiring perinatal hep B virus infection. Infected neonates have high levels of HBV replication and are at high risk for chronic infection, but are usually asymptomatic or have only mildly elevated liver function tests.

Question 70

What is basal cell carcinoma?

Answer 70

presents as a pearly, skin colored papule/nodule on the face. Biopsy classically shows nests of basaloid keratinocytes with peripheral palisading and clefting artifact. Unresected BCCs rarely metastasize but may undergo continued local growth, causing progressive surrounding tissue destruction.

Question 71

When to used a broad spectrum anticonvulsants versus narrow spectrum?

Answer 71

Broad spectrum anticonvulsants (eg, levetiracetam, valproic acid) treat both focal and generalized onset seizures, whereas narrow spectrum anticonvulsants (eg, carbamazepine, phenytoin) are primarily used only for focal onset seizures. Because the seizure in juvenile myoclonic epilepsy are usually generalized onset (ie, affect both cerebral hemispheres at onset), treatment is with a broad-spectrum agent such as valproic acid.

Question 72

Prolonged systemic hypertension leads to concentric left ventricular hypertrophy via?

Answer 72

the addition of myocardial contractile fibers in parallel. The thickening of the LV walls reduces LV compliance, leading to impaired diastolic filling and heart failure with preserved ejection fraction. In response to reduced cardiac output, the kidneys activate the renin-angiotensin-aldosterone system, stimulating sodium retention and vasoconstriction that worsens volume overload and can lead to decompensated heart failure.

Question 73

Streptoccous gallolyticus (S bovis) endocarditis and bacteremia are associated with?

Answer 73

gastrointestinal lesions (colon cancer) in 25% of cases. When S gallolyticus is cultured in blood, workup of colonic malignancy with colonoscopy is essential.

Question 74

Where does the ureter lie within the true pelvis?

Answer 74

The ureters pass posterior to the ovarian (gonadal) vessels within the retriperitoneum and cross anterior to the common/external iliac arteries to reach the true pelvis. Within the true pelvis, the ureters lie anterior to the internal iliac artery and posterior to the uterine artery.

Question 75

What is a left ventricular free wall rupture?

Answer 75

a mechanical complication that can occur within 5 days or up to 2 weeks following transmural (ST-elevation) myocardial infarction. Patients usually develop acute cardiac tamponade with hypotension and obstructive shock that rapidly leads to cardiac arrest.

Question 76

Short non-coding RNA sequences (eg, microRNA and small interfering RNA) induce?

Answer 76

posttranscriptional gene silencing by base pairing with complementary sequences within target mRNA molecules.

Question 77

Blastomyces dermatitides can cause?

Answer 77

pulmonary disease in the immunocompetent host. Dissemination (most commonly to skin and bones) occurs in immunocompromised individuals.

Question 78

What are crescents made of?

Answer 78

Cresent formation on light microscopy is diagnostic for rapidly progressive glomerulonephritis. Crescents consist of glomerular parietal cells, lymphocytes, and macrophages along with abundant fibrin deposition. Crescents eventually become fibrotic, disrupting glomerular function and causing irreversible renal injury.

Question 79

What is exogenous hyperthyroidism is characterized by?

Answer 79

elevated free thyroxine (T4), suppressed TSH, and low/undetectable thyroglobulin. It can occur with surreptitious levothyroxine misuse, animal-sourced thyroid supplements, and erroneous dosing of thyroid replacement therapy. Over time, the lack of TSH stimulation causes the thyroid follicles to become atrophic.

Question 80

Antibiotics exhibiting concentration-dependent killing can be administered using relatively high doses given at lower frequency. This allows for?

Answer 80

Effective microbial killing while preventing adverse effects that may occur with prolonged systemic exposure.

Question 81

What is von hippel lindau disease?

Answer 81

A cerebellar hemanioblastoma is associated with congenital cysts of the kidneys, liver, and/or pancreas is highly suggestive of von-hippel Lindau disease, a rare autosomal dominant condition.

Question 82

What is Hyper-IgE syndrome?

Answer 82

elevated IgE levels and is caused by impaired neutrophil activation and migration due to a defect in T-helper cell type 17 cells. Typical findings include noninflammatory (ie, cold) abscesses, recurrent sinopulmonary infections, and chronic atopic dermatitis.

Question 83

Which malignancies have a propensity for bony metastasis?

Answer 83

Clinical features that suggest a malignant cause of back pain include persistent pain at night, no relief with rest, onset at age >50, and systemic symptoms. Common malignancies have a propensity for bony metastasis: prostate, breast, kidney, thyroid, and lung.

Question 84

What is methadone?

Answer 84

a mu-opioid receptor agonist used for maintenance treatment for opioid use disorder; it is metabolized by the cytochrome P-450 system, particularly by CYP3A4. Certain inhibitors of CYP3A4 (eg, azoles, fluoxamine, ciprofloxacin, clarithromycin, cimetidine) can increase plasma methadone concentration and lead to opioid toxicity (eg, sedation, respiratory depression, miosis)

Question 85

What is benign paroxysmal positional vertigo?

Answer 85

causes brief (<1 min) episodes of vertifo triggered by changes in head position. Triggering an episode by using provocative head positioning maneuvers (eg, Dix-Hallpike) is diagnostic.

Question 86

What is familial adenomatous polyposis?

Answer 86

autosomal dominant hereditary disorder that results in the formation of innumerable colonic polyps and a nearly 100% risk of colorectal cancer. It arises due to germline mutation in the adenomatous polyposis coli tumor suppressor gene.

Question 87

What is Wernicke encephalopathy?

Answer 87

a complication of thiamine deficiency and is characterized by oculomotor dysfunction, encephalopathy, and ataxia. Chronic deficiency results in Korsakoff syndrome (eg, anterograde and retrograde amnesia, confabulation, apathy). Thiamine is involved in glucose metabolism, and areas of the brain with high metabolic demands are particularly susceptible; the mammillary bodies are most commonly affected.

Question 88

What is the cause of Meckel diverticulum?

Answer 88

The vitelline (omphalomesenteric) duct normally obliterates during early embyologic development. Incomplete obliteration can result in a spectrum of anomalies, including vitelline duct cyst (ie, cyst connected by fibrous bands to the ileum and umbilicus) and Meckel diverticulum.

Question 89

Genome wide association studies aim to identify associations between?

Answer 89

thousands of genetic variants and a disease. Because of the increase risk of false positive results when multiple tests are performed simultaneously, a smaller genome-wide p value is typically used.

Question 90

Pathogenesis of toxic shock syndrome

Answer 90

Toxic shock syndrome is typically associated with the prolonged use of tampons or wound packing, which allows Staph aureus to replicate locally and release pyrogenic toxic superantigens (eg, toxic shock syndrome toxin-1) into the blood. Superantigens bind to the MHC-II complex of antigen presenting cells without processing and nonspecifically activate T cells. This leads to a dramatic release of inflammatory cytokines, which causes the manifestations of the disease (eg, hypotension, high fever, organ failure, diffuse, erythematous rash)

Question 91

What is hyperosmotic volume contraction?

Answer 91

Volume contraction and expansion can be divided into isomotic, hyposmotic, and hyperosomotic states. Hyperosomotic volume contraction is caused by a loss of free water (with retention of electrolytes). It can occur in patients with diabetes insipidus or as a result of decreased fluid intake/excessive sweating.

Question 92

What nerves mediated the biceps and brachioradialis reflexes?

Answer 92

C5-C6

Question 93

What is a gliobastoma?

Answer 93

an aggressive primary brain neoplasm that generally presents with slowly worsening headache, seizure, and/or focal neurologic issues. Most cases are associated with oncogenic mutations that increase epidermal growth factor receptor expression on tumor cells, leading to increased transduction of growth signals that promote cellular survival and proliferation.

Question 94

What is bubonic plague?

Answer 94

Bubonic plague causes a febrile illness with regional inflammatory lymphadenopathy (buboes). The underlying pathogen is Yersinina pestis, a small gram-negative bacillus/coccobacillus that exhibits bipolar staining (resembling a closed safety pin). The major environmental reservoir is rodents; transmission usually occurs via rodent fleabite.

Question 95

What is anterior cord syndrome?

Answer 95

Ischemia of the anterior 2/3 of the spinal cord can occur with disruption of the anterior spinal artery blood supply. The resulting anterior cord syndrome causes bilateral distal loss of pain, temperature, and crude touch sensation (from injury to the spinothalamic tracts) and paralysis (from injury to the lateral corticospinal tracts).

Question 96

What is phase 1 clinical trials?

Answer 96

A phase 1 trial assesses the pharmacokinetics, pharmacodynamics, and safety profile (eg, adverse events, toxicity) of a new treatment in humans. It is usually conducted on a small number of healthy subjects.

Question 97

Transient ischemic attacks resulting in left leg weakness and vision loss in the right eye are likely due to?

Answer 97

emboli originating from the right internal carotid artery. The brachiocephalic artery branches from the aortic arch, then divides into the righ subclavian and right common carotid arteries. The left common carotid and left subclavian arteries branch directly from the aortic arch.

Question 98

What is osteogenesis imperfecta?

Answer 98

results from defective synthesis of type 1 collagen by osteoblasts. Clinical findings: history of fractures after only minimal trauma, blue sclerae, and small, malformed teeth. In most patients, osteogenesis imperfecta is transmitted by autosomal dominant inheritance.

Question 99

MOA of benzodiazepines?

Answer 99

bind GABA-A receptors, resulting in an increased frequency of chloride channel opening in the presence of GABA. Indications for prescribing include short-term treatment of anxiety disorders and alcohol withdrawal syndrome.

Question 100

Arteriovenous malformations can result in?

Answer 100

Arteriovenous malformations occur when an artery directly anastomoses with veins without an interposed capillary bed. They may result in spontaneous intracerebral hemorrhage or seizures, or they may be discovered incidentally when brain imahing is obtained for another reason.