NBME25 Flashcards
Vitamin D deficiency typically leads to?
Vitamin D plays a role in serum calcium and phosphate homeostasis by promoting the intestinal absorption of calcium and phosphate.
Vitamin D deficiency typically leads to decreased intestinal calcium absorption, hypocalcemia, increased PTH secretion, and increased PTH-mediated bone resorption.
What is positive predictive value?
defines the proportion of positive test results that are true positive
TP / (TP+FP)
What is negative predictive value?
defines the proportion of negative test results that are true negative
TN / (TN +FN)
Dysfunction of hepatocytes results in?
Hepatocytes are critical for the synthesis of multiple coagulation factors.
Dysfunction of hepatocytes results in an increased PT/INR secondary to the impaired synthesis of factor VII and may result in a predisposition to bleeding.
What is a confounding variable?
A confounding variable is one not controlled by the investigators that impacts both the intervention and outcome outside of the causal pathway.
Randomization is one way to minimize confounding variable bias.
What is squamous cell carcinoma of the lung?
Centrally located primary lung cancers include squamous cell carcinoma and small cell carcinoma of the lung.
Squamous cell carcinoma is the more common subtype and is associated with hypercalcemia because of paraneoplastic PTHrP production.
What is nephrogenic diabetes insipidus?
Nephrogenic diabetes insipidus is an adverse effect of lithium carbonate.
Lithium impairs the ability of the collecting tubule to reclaim free water by interfering with the pathway of antidiuretic hormone in the cells.
Patients typically present with polydipsia, polyuria, hyperosmolar serum, dilute urine, and failure to respond to desmopressin.
What is Haemophilus ducreyi?
A sexually transmitted infection that causes chancroid, which presents as one or more painful genital ulcers with associated inguinal lymphadenopathy.
A higher number of unprotected sexual encounters increases the patient’s risk for a sexually transmitted infection, and the epithelial discontinuity of the genital ulcers increases susceptibility to HIV.
What is the pathogenesis in osteoporsis?
Osteoporosis is characterized by an increase in osteoclast number and activity, which is driven by IL-1.
The balance of osteoblast and osteoclast interactions is key in the maintenance of bone mineral density. IL-1, also called osteoclast activating factor, can result in bone mineral density loss when increased.
Function of the superficial fibular nerve, deep fibular nerve, and tibial nerve
The peripheral nerves of the leg are often sites of compression injury or entrapment causing sensory loss and motor weakness.
The superficial fibular nerve everts the foot, while the deep fibular nerve dorsiflexes the foot, and the tibial nerve plantarflexes the foot.
Weakness in these movements can indicate which nerve is injured.
Acute, self-resolving viral syndromes (eg, yellow fever) follow a course that includes?
an asymptomatic period while the infectious agent is reproduced, followed by a symptomatic period that peaks, then improves with resolution of the infection.
What are the mediators of local muscle blood flow?
Adenosine, lactate, hydrogen ions, and the partial pressures of oxygen and carbon dioxide. These autoregulatory mediators serve to increase skeletal muscle blood flow during exercise.
What is radiation pneumonitis?
A potential sequela of radiotherapy for the treatment of malignancy. Fibrosis and contraction of lung tissue are characteristic of the later stages of radiation pneumonitis and can produce alveolar collapse and impaired gas exchange, a phenomenon known as atelectasis.
What causes chills?
Chills are involuntary, rapid muscle contractions which raise the body temperature in response to infection.
The response is mediated by pyrogenic cytokine activity on the hypothalamic thermoregulatory center.
What is seen with an aneurysm of the posterior communicating artery?
Aneurysms of the posterior communicating artery may compress the ipsiltaral oculomotor nerve, resulting in diplopia, mydriasis, exotropia, and hypotropia.
They are diagnosed on CT angiography, MR angiography, or conventional angiography.
What is the contemplation stage of behavioral change?
Refers to ambivalence about changing a behavior, in which the patient expresses knowledge of the consequences of their detrimental behavior but is not yet prepared to make plans to change.
Motivational interviewing is a technique used by physicians to promote a patient’s readiness for change.
What is a type II HSR?
Type II HSR is characterized by the formation of antibodies to cell surface antigens.
Both erythroblastosis fetalis and Graves disease are examples.
Constriction of the SMA occurs in?
duodenal volvulus from intestinal malrotation; the SMA is embryologically related to the midgut and in turn shares a common mesentery with the duodenum, which twists during the volvulus.
What is an acoustic neuroma?
Acoustic neuromas, benign tumors of Schwann cells that arise from the vestibulocochlear nerve, can compress the cerebellar peduncles. Acoustic neuromas can cause ipsilateral hearing loss and positional dizziness and, if compressing the cerebellar peduncles, can lead to ipsilateral dysmetria.
What is the uterosacral ligament?
The uterosacral ligament is a paired structure that extends bilaterally from the cervical region to the sacrum, helping to support the uterus in the pelvis.
What should raise suspicion for primary CNS lymphoma?
Solitary brain lesions in patients with HIV/AIDS, particularly when associated with low CD4+ count and a high viral load, should raise suspicion for primary CNS lymphoma.
Alternative diagnoses include a bacterial abscess, cerebral toxoplasmosis, primary brain tumors, and metastatic lesions.
MOA of DPP-4 inhibitors (-glips)
DPP-4 inhibitors prevent the early breakdown of incretins, which promote endogenous insulin release.
Sitagliptin is an example. They are generally used once metformin, diet, exercise, weight loss, or additional medications have failed to appropriately control a patient’s blood glucose.
Primary hyperparathyroidism is most commonly caused by?
parathyroid adenoma, followed by parathyroid hyperplasia, and parathyroid carcinoma.
What happens with FSH levels in pregnancy?
FSH increases during the follicular phase of the menstrual cycle in order to support the developing ovarian follicle.
It surges at the time of ovulation, followed by a precipitous drop, and then subsequently slowly increases during the luteal phase, preparing to support the developing follicle of the next cycle.
Where does the breakdown of dipeptides and tripeptides into amino acids take place?
Dipeptides and tripeptides are produced by the activity of trypsin and chymotrypsin within the lumen of the duodenum.
Free amino acids are produced upon further digestion of these small peptides within the brush border of the intestinal mucosa.
Asthma exacerbations, secondary to a reversible obstruction to airflow, typically presents with?
respiratory alkalosis because of hyperventilation when mild. If severe, symptoms of respiratory distress will remain present (eg, shortness of breath, tachycardia, tachypnea, hypoxia, poor air movement, biphasic wheezing, accessory muscle use) and the arterial blood gas analysis may appear within reference ranges or demonstrate developing or worsening respiratory acidosis.
Cryptorchidism is associated with?
Cryptorchidism, or failure of one or both testes to descend into the scrotum, is associated with an increased risk for testicular germ cell tumor development.
Testicular germ cell tumors include seminomas, choriocarcinomas, teratomas, and embryonal carcinomas.
When does reperfusion injury occur?
Reperfusion injury occurs when tissue oxygenation is restored following a period ischemia.
This occurs because of the generation of free oxygen radicals and peroxides which result in lipid peroxidation, protein modification, and DNA strand breaks.
What is convenience sampling?
a non-random, non-probability-based method of sampling, where the sample under study includes participants who were easy to contact and willing to enroll.
Examples include studying a classroom full of students who happen to be in the same place, or emailing persons within an organization (eg, resident physicians in a hospital.
As the thyroid produces thyroxine and triiodothyronine, these hormones exert negative feedback on the hypothalamus and pituitary, resulting in?
the decreased production of TRH and TSH in primary hyperthyroid states.
Upper motor neuron injuries lead to?
hyperreflexia and/or spasticity as the descending motor neurons no longer provide inhibitory inputs to the lower motor neurons of the reflex arcs.
Lower sensory or motor neuron lesions interrupt the reflex arc, thereby causing hyporeflexia.
Basal cell carcinoma is derived from?
Basal cell carcinoma is the most common form of skin cancer and is derived from the basal cells of the epidermis.
Increases in the ratio of ATP:ADP leads to?
lead to islet cell depolarization by closing potassium-ATP channels. Calcium ions enter the cell, triggering the exocytosis of pre-formed insulin.
Uncoupling protein prevents some of the proton gradient in a mitochondrion from being used in the synthesis of ATP. Blocking such a protein would theoretically increase the cell’s ATP:ADP ratio.
How do natural killer cells work?
Natural killer cells use perforin and granzyme to induce apoptosis in virally infected or neoplastic cells that do not express MHC class I antigens.
How does chronic pancreatitis effect bicarbonate?
Chronic pancreatitis impairs bicarbonate (reduces duodenal pH) release from pancreatic acinar cells, predisposing to pancreatic autodigestion and abnormally acidic duodenal contents, which commonly presents as recurrent abdominal pain.
Where does hydrochlorothiazide act on the nephron?
The nephron is composed of a glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.
HCTZ acts at the distal convoluted tubule to inhibit sodium and chloride reabsorption and promote diuresis.
What causes beta-thalassemia?
There are two b-globin genes, with on inherited from each parent. Mutations or deletions of one copy produces a mild disease called b-thalassemia minor while deletion or mutation of both genes causes b-thalassemia major, which is characterized by severe anemia from ineffective erythropoiesis and hemolysis. Point mutations affecting splice sites and promoter sequences are the most common cause.
What is seen in heroin withdrawal?
Heroin withdrawal demonstates symptoms that are common to other CNS depressants such as restlessness, tachycardiac, and hypertension, tremors, and nausea and vomiting.
However, lacrimation, rhinorrhea, piloerection, and yawning are much more typical for heroin withdrawal than for other CNS depressants.
What is seen if the supraspinatus tendon is injured?
The supraspinatus tendon is commonly injured or impinged during overhead motion.
Abduction with internal rotation of the arm can produce pain with impingement of the injured tendon.
What is the pathogenesis behind seasonal allergies?
The symptoms of seasonal allergies are secondary to the vasodilation and increased capillary permeability caused by histamine.
What is acute T lymphocyte-mediated rejection?
typically occurs within months following transplantation and presents with allograft dysfunction.
Kidney biopsy demonstrates lymphocytes in the interstitium, tubules, glomeruli, and blood vessels.
What is mixed cryoglobulinemia?
Increased cryoglobulin concentrations are characteristic of mixed cryoglobulinemia, which often presents with palpable purpura in association with arthralgias and peripheral neuropathy caused by immune-complex mediated vasculitis.
Chronic hep C virus is the most common infection associated with cryoglobulinemia.
Drug eruptions can cause?
Drug eruptions are a common cause of widespread rashes.
Morbilliform, or maculopapular, drug eruptions typically occur 7 to 10 days after medication initiation. Most common culprits include antibiotics, sulfa-containing drugs, and antiepileptics.
What is the pathogenesis of the apoptosis of hepatocytes in viral hep A or yellow fever?
Acute hepatic inflammation in the setting of viral hepatitis A or yellow fever may cause apoptosis of hepatocytes.
This occurs via the extrinsic pathway of apoptosis and is seen on histology as ballooning hepatocytes and apoptotic bodies.
Role of lipase
Lipids, including triglycerides, cholesterols, and free fatty acids form an important part of the diet of a breast-fed infant.
Lipase, especially lingual lipase, plays an important role in infant digestion by hydrolyzing triglycerides into free fatty acids and monoglycerides, which can be absorbed by intestinal enterocytes.
What is carbidopa?
Carbidopa cannot cross the blood brain barrier and therefore increases the bioavailability of levodopa without inhibiting the conversion of levodopa to dopamine in the brain.
Carbidopa also decreases peripheral dopamine concentrations, reducing the likelihood of dopamine-related side effects such as nausea.
What does a higher Km mean?
Enzymatic mutations may altar the affinity or velocity of an enzyme for its substrate, marked by deviation from normal in Km or Vmax.
A higher Km indicates decreased affinity of the enzyme active site for the substrate.
What are proteoglycans?
Proteoglycans comprise the extracellular matrix and are a key element of articular cartilage.
In disease states where cartilage breaks down, such as osteoarthritis, decreased proteoglycan secretion would be expected.
How does epinephrine play a role in glucose homeostasis?
Epinephrine plays a critical role in glucose homeostasis through its action on adrenergic receptors located on the liver, the activation of which results in glycogenolysis and gluconeogenesis. The selective activation of medullar epinephrine release may reflect the critical need for epinephrine to serve this function during times of hypoglycemia.
The kidneys synthesize what in states of hypoxemia?
The kidneys synthesize EPO in states of hypoxemia, which promotes the synthesis of new red blood cells to increase oxygen carrying capacity.
Chronic kidney disease leads to anemia via the reduced synthesis of EPO.
What is the Hardy Weinberg equilibirum?
Assuming Hardy Weinberg equilibrium, the frequency of a dominant and recessive allele within a population can be determined using the equations p + q = 1 and p^2 + 2pq + q^2 = 1, where p and q are the allele frequenies of the two alleles in question.
The total number of alleles at a single given nucleotide in a population is equal to two times the number of individuals in the population
What is seen in strokes affecting the paracentral lobule?
The lower extremity is controlled by the medial aspects of the precentral (motor) and postcentral (sensory) gyri in the region referred to as the paracentral lobule.
Strokes affecting this region result in the loss of motor and sensory function of the contralateral lower extremity.
What brain structure is atrophied in Wernicke-Korsakoff syndrome?
Chronic alcohol use disorder and associated malnutrition may result in significant vitamin B1 (thiamine) deficiency, which can cause Wernicke-Korsakoff syndrome.
The syndrome is characterized by symptoms such as altered mental status, ophthalmoplegia, ataxia, and retrograde and anterograde amnesia.
The mammillary bodies are classically atrophied.
Function of fatty acid synthase?
In the fed state, enzymes that catalyze reactions leading to the formation and storage of energy rich molecules (eg, glycogen, fatty acids) are upregulated.
The activity of fatty acid synthase is upregulated following a meal, with insulin acting as a key activating signal.
Mutations that cause dysfunction or absence of the LDL receptor results in?
The cytoplasmic domain of the LDL receptors is responsible for signaling that leads to endocytosis, so mutations at this location allow for normal binding of LDL but an inability to transport it across the membrane.
Mutations that cause dysfunction or absence of the LDL receptor result in familial hypercholesterolemia.
What kind of meds help for hypertrophic cardiomyopathy?
The left ventricular septum is asymmetrically thickened in hypertrophic obstructive cardiomyopathy, leading to outflow tract obstruction and diastolic dysfunction.
Medication that decrease the heart rate improve symptoms by allowing more time for diastolic filling, which increases left ventricular preload and decreases the degree of left ventricular outflow tract obstruction
Glucocorticoids such as prednisone primarily exert their anti-inflammatory properties by inhibiting the production and function of?
T lymphocytes. Prolonged use has myriad consequences including impaired lipid metabolism, insulin resistance, and deleterious effects on bone health.
Function of beta-lactamases
B-lactamases inactivate b-lactam antibiotics ( penicillin and ampillicin) and are a common mode of resistance to the b-lactam class among gram negative bacteria
What is important for tumor grading?
Tumor grading describes the cellular and histologic features of a tumor.
The number of mitoses per unit area, when increased, reflects active cell growth and division within a tumor.
What is inhalant abuse?
can manifest with perioral and perinasal dermatitis, conjunctival injection, unusual breath odor, nausea, anorexia, respiratory symptoms, and neuropsychiatric symptoms such as irritability and mood swings. The rash may contain paint or glitter depending on the type of inhalant.
In the setting of an inferior vena cava obstruction, what is the route of blood from the lower extremities?
The lumbar, azygos, and hemiazygos veins provide an alternate route for blood from the lower extremities to return to the superior vena cava in the setting of an inferior vena cava obstruction.
What is seen in rheumatoid arthritis?
Rheumatoid arthritits is a common autoimmune disease characterized by joint destruction, pain, and upregulation of immunomodulatory cytokines.
In rheumatoid arthritis and similar inflammatory states, inflammatory cells, interleukins, and tumor necrosis factors are increased.
In this setting, complement activation results in the consumption of complement proteins, resulting in decreased concentrations within the synovial fluid.
What is acute pyelonephritis?
typically presents with a fever, chills, myalgias, and systemic symptoms such as nausea and vomiting, most commonly in a female patient following symptoms of a lower urinary tract infections.
On histology, lymphocytic and neutrophilic infiltrates are seen adjacent to and within the tubules, and urinalysis may show pyuria and white blood cell casts
What is seen on MRI for multiple sclerosis?
Multiple sclerosis is an immune mediated demyelinating disease that present with episodic focal neurologic symptoms that occur in different anatomic locations; optic neuritis is a common initial presentation.
MRI classically shows white matter hyperintensities in periventricular locations.
What can happen with a central catheter inserted at the internal jugular vein?
Central venous catheter insertion is indicated for volume resuscitation, emergency vascular access, adminstration of vasopressors or other caustic medications, and facilitates interventions such as plasmapheresis, hemodialysis, and intracardiac pacing.
A potential site of central catheter insertion, the internal jugular vein, is adjacent to the ling and common carotid artery, and complications from puncturing or injuring these structures include pneunothorax and hematoma or hemorrhage, respectively.
The use of monoclonal antibody therapy against TNF-alpha is associated with an increased risk for?
reactivated latent mycoplasma tuberculosis. Because of this, all prospective candidates for this therapy should be screened for latent mtb and accordingly treated if positive.
What is relative risk?
the risk for developing disease in a group with an exposure divided by the risk for developing disease in a group without the exposure
RR = (a / a+b) / (c / c+d)
What is the incidence of VSD?
The baseline population VSD incidence is approximately 2-3%, with inheritance patterns that do not follow conventional Mendelian patterns apart from those associated with known genetic syndromes
Which neurotransmitter is associatd with excitotoxicity?
Glutamate and excitatory neurotransmitters are associatd with excitotoxicity.
Excitotoxicity causes neuronal loss via apoptosis, often in the setting of an ischemic, traumatic, or substance induced insult to the central nervous system
What is idiopathic pulmonary fibrosis?
Pulmonary fibrosis results from chronic inflammation of the pulmonary interstitium, classically presenting with dyspnea and a nonproductive cough.
Idiopathic pulmonary fibrosis demonstrates a usual interstitial pneumonitis pattern on both imaging and histology.
What is recombination?
Recombination takes place in prophase I of meiosis and is the process by which two alleles closely located on the same chromatid can be separated.
If the genotype at only one of these sites is known, linkage analysis allows for the prediction of the likelihood of inheriting a given allele at the other site.
What is seen in colorectal carcinoma of the ascending colon?
CRC of the ascending colon is typically exophytic in nature, making it less likely to present with symptoms of obstruction, such as abdominal pain or stool caliber change.
During its insidious growth, it can result in chronic, slow blood loss, which can manifest as progressive, gradual onset microcytic anemia
What is a cholesterol emboli?
Interventional procedures increase the risk for atherosclerotic plaque disruption, especially during manipulation of the aorta, which can lead to cholesterol emboli.
Dermatologic symptoms include localized petechiae, livedo reticularis, and blue toe syndrome, with needle-shaped clefts on histologic examination
Role of prosterone
Progesterone is the hormone responsible for maintaining the endometrial lining when implantation occurs.
Without enough progesterone, spontaneous abortion ensues as a result of endometrial sloughing.
What buffers the concentration of calcium ion in the sarcoplasmic reticulum?
Calcium is the central element in the excitation-contraction coupling. It is stored in the sarcoplasmic reticulum, where it is buffered by calsequestrin.
When calcium is released, it results in displacement of tropomyosin and triggers sarcomere contraction through myosin and actin cross-bridging.
What is a case control study?
Case-control studies group patients according to disease outcome status and analyze the odds of exposure to a hazard. The appropriate statistical measure of case control studies is the odds ratio.
What are satellite cells?
Satellite cells are found in skeletal muscle and function to repair damaged myofibrils.
They are not found in cardiomyocytes, which are unable to undergo regeneration following myocardial infarction or injury.
Where is the lingular bronchus located?
a distinct projection of the left upper lobe, which can be accessed by bronchoscopy through the left upper lobe bronchus
REM sleep is characterized by?
increased total brain synaptic activity. Therefore, cerebral blood flow increases during REM sleep
What is the crus cerebri?
The crus cerebri carries fibers from the lateral corticospinal tract. Lesions to the crus cerebri lead to contralateral upper motor neuron weakness because of the caudal decussation of the lateral corticospinal tract in the medulla
What is the inferior thoracic esophagus supplied by?
arterially supplied by branches directly from the aorta that must be ligated during an esophagetomy.
Below the diaphragm, the esophagus is supplied by the left gastric artery and short gastric branches
Function of ADH (vasopressin)
ADH regulates the V2 receptors in the collecting tubule and promotes the uptake of free water via aquaporins; the collecting tubules are located within the renal medulla and terminate in the renal papillae.
Renal papillary necrosis results in the loss of the renal papillae and associated substructures, which can be triggered by infections, diabetes, sickle cell, or NSAIDS.
In the setting of renal papillary necrosis, ADH is unable to act on the collecting ducts of the nephron
What is VDJ rearrangement?
a process that occurs in B lymphocytes in the bone marrow, and in T lymphocytes in the thymus, resulting in the generation of completely novel Its and T lymphocyte receptors, respectively.
Because T lymphocytes circulates as either completely rearranged or unrearranged cells, application of a region specific probe (eg, J region) should demonstrate the presence of a single J gene (1.5 kb) or multiple J genes (6 kb). The presence of a 6 kb band signifies the presence of a T lymphocyte with an unrearranged Ig gene
What is Ornithine transcarbamylase deficiency?
ornithine transcarbmylase deficiency is an X linked recessive condition and the most common urea cycle disorder.
It results in the accumulation of nitrogenous wastes and is diagnosed based on serum concentration of urea cycle reactants and products.
It generally presents in infancy and can be fatal because of the neurotoxic effects of ammonia.
Adverse effect of doxorubicin chemotherapy
Cardiotoxicity leading to dilated cardiomyopathy is a well known adverse effect of doxorubicin chemotherapy.
This occurs secondary to an increased concentration of reactive oxygen species and subsequent lipid peroxidation of myocyte membranes
What organs cannot be visualized during an intraperitoneal surgery?
Laparoscopic cholecystectomy is a minimally invasive surgical procedure that occurs within the peritoneal space.
Retroperitoneal organs, including the pancreas, cannot be easily visualized during an intraperitoneal surgery.
What is osteitis deformans (Paget disease)
characterized by increased osteoclast activity during the lytic phase, followed by osteoblast activity during the blastic phase, resulting in the synthesis of sclerotic, woven bone.
Labs: increase serum alkaline phosphatase
MOA of praziquantel
altered parasite calcium homeostasis through increasing membrane permeability.
Calcium influx into the cytosol causes paralysis, dislodgement of the parasite position within host organs, and death of the parasite
Part of nephron that is most susceptible to decreased afferent blood flow?
The proximal convoluted tubule is the most susceptible to decreased afferent blood flow and oxygen delivery compared to the other parts of the nephron because it is highly metabolically active and is situated in a watershed zone of the renal cortex
Movement of fluid between capillaries and the lymphatic system is dependent on?
the hydrostatic and oncotic pressures of both the capillary and interstitial compartments.
High capillary hydrostatic pressure and low plasma oncotic pressure will increase the movement of fluid out of the capillaries and into the interstitial space, which increases lymphatic flow.
Conversely, high interstitial fluid hydrostatic pressure and low interstitial fluid oncotic pressure will drive fluid back into the capillaries and away from the lymphatic system.
