NBME26 Flashcards
Lesch-Nyhan syndrome has impaired salvage of which purines?
Lesch-Nyhan syndrome presents with intellectual disability, aggressive behavior, self mutilation, gout, and dystonia.
Mutations in HGPRT cause this disorder by impaired salvage of the purines guanine and hypoxanthine, which leads to increased levels of xanthine and uric acid.
Hyperuricemia in Lesch-Nyhan syndrome is treated with xanthine oxidase inhibitors, such as allopurinol or febuxostat, in order to reduce synthesis of uric acid.
MOA of mannitol
Mannitol, an osmotically active carbohydrate monomer, raises serum osmolality when given as an infusion.
Osmoreceptors detect the change in osmolality and trigger the production of antidiuretic hormone by the hypothalamus
Respiratory depression results in hypoventilation, which is characterized by?
hypoxemia, respiratory acidosis (Due to CO2 retention) and a normal alveolar-arterial gradient on arterial blood gas analysis.
An increase A-a gradient is seen in conditions that cause V/Q mismatch, shunt, and/or diffusion limitation
Function of adenosine diphosphate
ADP rapidly and irreversibly causes platelet aggregation through its action on the P2Y1 and P2Y12 receptors
What is placenta accreta?
the abnormal attachement of the placenta directly to the myometrium, which most commonly presents with retained products of conception and postpartum hemorrhage.
Risk factors: prior uterine instrumentations (including cesarean delivery), increased maternal age, placenta previa, and multiparity.
Given the high risk of morbidity and mortality, elective surgical delivery at 34 to 36 weeks is recommended.
Giant cell pneumonia is a severe complication of?
measles that is rare in patients who ar not immunosuppressed.
Histo: inclusion bodies and multinucleated giant cells in the respiratory epithelium
What is the function of the pelvic parasympathetic nerves in the pelvic nerve plexus?
function to excite and contract the bladder via muscarininc acetylcholine receptors while sympathetic nerves control the function of the internal urethral sphincter via alpha-1 adrenergic receptors, leading to normal urination.
Damage to the pelvic nerve plexus can affect both bladder contraction and internal sphincter relaxation, leading to overflow incontinence
MOA of doxycycline
prevents the attachment of aminoacyl-tRNA to ribosomes
Adverse effects of doxyclicine
gastrointestinal distress, photosensitivity, and in children- discoloration of teeth and inhibition of bone growth, which makes it contraindicated in pregnancy
The testes drain which veins?
The testes are drained by the gonadal veins, which drain into the left renal vein on the left side and directly into the inferior vena cava on the right side.
Obstruction of or increased pressure within the left gonadal vein or left renal vein leads to a left-sided varicocele
When does oxidation of fatty acids occur?
Oxidation of fatty acids in the mitochondrial matrix occurs during a state of starvation, or a state with increased glucagon levels, in order to maintain nutrition when glycogen stores have been depleted.
What is seen in folate deficiency?
Folate deficiency is often seen in patients with malnutrition, alcoholism, or high cell turnover conditions such as acute leukemia and sickle cell disease.
It is associated with megaloblastic anemia, hypersegmented neutrophils, erythrocyte macrocytosis, and increased serum homocysteine levels with normal methylmalonic acid levels.
What is anemia of chronic disease
anemia of chronic disease is a common finding in autoimmune and inflammatory diseases, chronic infections, and malignancy.
Increased hepcidin levels decrease intestinal iron absorption and increase iron storage in the bone marrow and reticuloendothelial system, preventing use of iron by erythrocyte precursors, thereby resulting in anemia.
What is responsible for granuloma formation in tuberculosis?
MTB infects macrophages and results in granuloma formation within the lungs via the actions of IL-12 and interferon-gamma on macrophages, Th1 helper T cells, and NK cells.
What is zollinger-ellison syndrome?
Zollinger-Ellison syndrome stems from a gastrin-secreting tumor located typically within the pancreas or duodenum that results in excessive production of acid by the gastric parietal cells.
Patients develop recurrent, chronic duodenal or jejunal ulcers, which can present with abdominal pain, diarrhea secondary to malabsorption, and possible hematemesis, melena, or hematochezia.
Immunohistochemical labeling of neoplastic cells will reveal positive staining for gastrin.
The precentral gyrus of the frontal lobe contains?
the primary motor cortex controlling the voluntary movement of the contralateral body.
Laterally, the precentral gyrus controls the contralateral face.
pathology affecting the upper motor neuron innervation to the contralateral face typically presents with only lower face weakness as the facial nerve nucleus that controls forehead musculature is dually innervated by upper motor neurons from bilateral precentral gyri.
What is chromosome instability?
There are two primary mechanisms of genomic instability in the pathogenesis of colon cancer: microsatellite instability (15% of cases) and chromosome instability (85%).
Chromosome instability results initially in activating mutations of oncogenes and/or loss of function mutations of tumor suppressor genes, resulting in the consequent aberrant entry into the cell cycle.
Once cells enter mitosis, genomic instability occurs during chromosome replication (S phase), fidelity checks of the chromosomes (G2 phase), and during separation of the chromosomes (M phase), which results in the accumulation of mutations, potentially causing increased proliferation and resistance to chemotherapy.
Hardy-Weinberg equilibrium models what?
the frequency of alleles within a population from generation to generation, which considered alleles to be in stable equilibrium over time.
Violation of its assumptions will cause deviation from this ideal behavior and variation in the prevalence of alleles over time.
Movement of fluid between capillaries and the interstitial space is dependent on the hydrostatic and oncotic pressures of both 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.
High interstitial fluid hydrostatic pressure and low interstitial fluid oncotic pressure will drive fluid back into the capillaries and away from the interstitial space
What is central retinal artery occlusion?
presents with sudden, painless, monocular vision loss, relative afferent pupillary defect, retinal whitening with a cherry red spot, and retinal arteriolar narrowing with boxcarring.
The most common cause of CRAO is a retinal artery embolism from a carotid artery atheroma or a cardiac valvular vegetation. CRAO is considered a form of embolic stroke affecting the eye, and suspicion of CRAO should therefore prompt an immediate stroke risk factor.
Induction time of anesthesia with volatile anesthetics depends on?
the blood solubility of the anesthetic, cardiac output, and minute ventilation.
Low blood solubility decreased cardiac output, and high minute ventilation will increase the speed of induction.
Conversely, high blood solubility, increased cardiac output, and low minute ventilation will decrease the speed of induction
Damage to the mesial temporal lobe leads to?
Memory and emotional regulation are mediated by the limbic system, which includes the hippocampus, parahippocampal gyrus, and amygdala, located in the mesial temporal lobe.
Cancer-related radiation and chemotherapy commonly damage these mesial temporal lobe structures, leading to emotional dysregulation and the development of short term memory loss.
Function of prostaglandin E2
potent bronchodilator that acts by stimulating adenylyl cyclase in smooth muscle cells to increase the intracellular concentration of cAMP.
cAMP leads to smooth muscle relaxation by inhibiting myosin light chain kinase
Proliferative endometrium is present during the follicular phase of menstruation prior to ovulation. What is seen histo?
straight uterine glands, extension of the spiral arteries, and abundant stromal cells/
What is long chain acyl-coA dehydrogenase deficiency?
AR disorder of fatty acid metabolism. Signs and symptoms include irritability, lethargy, hepatomegaly (due to excess fat accumulation) and hypoglycemia.
Episodes can be triggered by illness, fasting, stress or exercise.
Immediate treatment involves correction of hypoglycemia and long term management involves preventing acute episodes of hypoglycemia and dietary supplementation with medium chain fatty acids.
function of histone acetyltransferase?
serves to add acetyl groups to histone lysine residues, causing a decreased affinity of histone for DNA.
This results in relaxation of the DNA histone complex (euchromatin), which allows for gene transcription
What is a parasternal heave?
most commonly associated with right ventricular hypertrophy, which is the most anterior chamber of the heart.
Right ventricular hypertrophy results from pulmonary hypertension, which is frequently a complication of chronic lung disease due to hypoxia induced pulmonary vasoconstriction and vascular remodeling
What is neonatal respiratory distress syndrome?
characterized by the reduced production of pulmonary surfactant. Surfactant is critical for reducing alveolar surface tension and collapsing pressure; without it, alveolar collapse results in impaired gas exchange, decreased lung compliance, and increased lung elastic recoil
What is the most common cause of primary hyperparathyroidism?
Parathyroid chief cell adenoma, and presents with symptoms of hypercalcemia, including reccurent nephrolithiasis, bone pain from osseous resorption, polyuria, dehydration, constipation and psychiatric disturbances
What is meckel diverticulum?
results from persistence of the vitelline duct and presents as an approximately two inch diverticulum located two feet proximal to the ileocecal valve.
It can cause abdominal pain, hematochezia, or melena.
Meckel diverticulum frequently harbors ectopic tissue, which is most commonly gastric or pancreatic tissue. Rarely, Meckel diverticulum may contain ectopic endometrial tissue
Large arteriovenous fistulas can result in?
high-output cardiac failure. The abnormal connection between an artery and vein results in decreased systemic vascular resistance and an increased venous return to the right heart, with a consequent increase in stroke volume and cardiac output
What is the incidence rate of disease in a population?
equals the number of new cases of the disease divided by the number of persons at risk for contracting the disease.
Incidence is a measure of risk and is the porbability of a given condition occuring within a specified period of time. Importantly, when individuals are added to or are removed from a population, the denominator must also change to reflect the new number of persons at risk for contracting the condition
Atypical lymphocytes in infectious mononucleosis are?
Infectious mononucleosis is a viral illness caused often by infection with EBV.
While EBV infects B lymphocytes through CD21, the atypical lymphocytes seen on peripheral blood smear are cytotoxic CD8+ T lymphocytes reacting to the viral infection
What pathway produces ketone bodies?
During a prolonged fasting state (greater than 3 days), the brain is dependent upon ketone bodies as its primary source of energy.
Beta-oxidation, which requires the carnitine-acylcarnitine cycle to transfer acyl groups from the cytoplasm to the matrix, allows for the production of ketone bodies. This manifests on labs with hypoglycemia, metabolic acidosis, and ketonuria
