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.
