Uworld14 Flashcards
Beta-2 receptors can be found?
Although beta-2 receptors are predominany in the lungs and vasculature, they are also found on all cell membreanes, including those of the uterus.
Stimulation of uterine receptors results in smooth muscle relaxation (tocolysis), while stimulation of sodium-potassium ATPase pumps can result in hypokalemia
MOA of nonbenzodiazepine meds (zolpidem, zaleplon, eszopiclone)
stimulate specific subtypes of GABAa receptors.
As a result, nonbenzodiazepines are primarily hypnotics and do not produce the anxiolytic, muscle relaxant, or anticonvulsant effects associated with benzodiazepines
Histopath for melanoma
Melanoma is a highly aggressive malignancy that often metastasizes early in the disease course.
Patients may be asymptomatic for years prior to onset of metastatic manifestations.
Diagnosis is generally made when a histopathologic sample shows cellular atypia with cells containing brown pigment (melanin granules); immunostaining for melanocytic markers (S-100, HMB-45) is generally positive
What is neonatal abstinence syndrome due to?
maternal opioid use causes neurologic, gastrointestinal, and autonomic symptoms; irritability, tremors, diarrhea, and sneezing are classic findings.
Patients with symptoms refractory to nonpharmacologic therapy warrant opioid replacement (morphine)
What is seen in patients with severe iron def anemia?
typically have evidence of hypochromic, microcytic erythrocytes on peripheral blood smear with poikilocytosis.
Labs reveal low red blood cell count, low hepcidin, and high transferrin.
Although erythropoietin is markedly elevated in iron def anemia, there is not enough iron to efficiently generate erythrocytes; therefore reticulocyte count is low
mineralocorticoid receptor antagonists (spironolactone, eplerenone) improve survival in patients with?
congestive heart failure and reduced left ventricular ejection fraction.
They should not be used in patients with hyperkalemia or renal failure
What is seen in radial nerve injury?
Radial nerve injury can occur with repetitive pressure/trauma at the axilla (eg, improperly fitted crutches)
Findings: weakness of the forearm, hand, and fingers extensors (wrist drop, absent triceps reflex) and sensory loss over the posterior arm and forearm, dorsolateral hand, and dorsal thumb. More distal lesions spare the triceps brachii
What is diabetic autonomic neuropathy?
Prolonged hyperglycemia in diabetes mellitus can injure the parasympathetic and sympathetic nervous system, resulting in diabetic autonomic neuropathy.
This can lead to disordered small bowel and colonic motility and increased intestinal secretions, resulting in secretory-like diarrhea (eg, fasting bowel movements)
Stapedius muscle is innervated by?
the stapedius nerve (a branch of the facial nerve).
Paralysis of the stapedius muscle results in hyperacusis (increased sensitivity to sound)
What causes hypokalemia resulting from the intracellular shift of potassium?
Betaa-adrenergic hyperactivity (beta-2 agonists, endogenous epinephrine release), increase insulin levels, elevated extracellular pH, or increased cell production (eg, acute leukemia)
Functions of glucagon
Glucagon increases glucose by increasing hepatic glycogenolysis and gluconeogenesis.
Stimulates insulin secretion from the pancreas.
Unlike epinephrine, glucagon has an insignificant effect on glucose homeostasis in the skeletal muscle, adipose tissue, and renal cortex.
What are the most common findings with posterior cerebral artery stroke?
Contralateral homonymous hemianopia with macular sparing due to damage to the occipital cortex and contralateral hemisensory loss due to damage to the thalamus
Chronic kidney diseases causes disordered mineralization and bone metabolism that usually presents with?
Hyperphosphatemia, secondary hyperparathyroidism, and decreased calcitriol levels.
Patients can be asymptomatic or develop weakness, bone pain, and fractures.
How does estrogen effect thyroid?
An increase in estrogen activity (pregnancy, postmenopausal estrogen replacement therapy), increases the level of thyroxine-binding globulin.
This leads to an increase in total thyroid hormone levels, but feedback control maintains normal levels of free (biologically active) thyroid hormone
What is Campylobacter gastroenteritis?
Typically acquire from contaminated poultry or domesticated animals (eg, dogs), causes an inflammatory diarrhea characterized by fecal leukocytes and red blood cells.
Manifestations include fever, abdomina pain, and diarrhea that may be grossly bloody
What happens when carbon monoxide binds heme?
Carbon monoxide binds heme iron in hemoglobin with an affinity much greater than oxygen, generating carboxyhemoglobin.
Remaining binding sites on carboxyhemoglobin have an increased affinity for oxygen that causes the oxygen dissociation curve to shift to the left, impeding oxygen delivery to tissues
In a young Caucasian patient, the combo of recurrent respiratory infections with Pseudomonas aeruginosa, diarrhea, and failure to thrive suggests a diagnosis of?
Cystic fibrosis.CF causes steatorrhea and failure to thrive due to malabsorption secondary to pancreatic insufficiency, which can be corrected by pancreatic enzyme supplementation.
Gastroesophageal reflex disease is caused primarily by?
gastroesophageal junction incompetence and can be associated with extraesophageal symptoms (eg, nocturnal cough) in the absence of heartburn (“silent GERD”).
Acidic gastric contents irritate the esophageal mucosa, leading to characteristics histologic findings that include basal zone hyperplasia, elongation of the lamina propria papillae, and scattered eosinophils
DiGeorge syndrome results from?
Maldevelopment of the 3rd (inferior parathyroid and thymus) and 4th (superior parathyroid) pharyneal/branchial pouches.
Subsequent parathyroid and thymic hypoplasia results in hypocalcemia and T cell deficiency
What is X-linked agammaglobinemia?
an immunodeficiency characterized by low circulating B lymphocytes and immunoglobins, should be suspected in an infant with severe, life-threatening enteroviral infection.
Impaired tetrahydrobiopterin (BH4) synthesis inhibits?
conversion of phenylalanine to tyrosin because BH4 is an essential cofactor of phenylalanine hydroxylase.
BH4 is also a cofactor for hydroxylase enzymes in the synthesis of essential neurotransmitters (dopamine, serotonin)
Preparation stage in the stages of change model
In the transtherorectical stages of change model, the preparation stage represents the stage in which the individual has committed to behavioral change and is considering change strategies but has not determined or instituted a specific course of action.
Individuals at this stage may be weighing options and seeking additional support.
Acute benzodiazepine (eg alprazolam, lorazepam) overdose causes what to the respiratory system?
causes central respiratory depression with hypoventilation.
The hypoventilation leads to CO2 retention and acute respiratory acidosis.
It also decreases the PAO2, leading directly to hypoxemia (PaO2 <75mmHg). The efficiency of gas transfer between the lungs and the circulation is intact; therefore, a normal alveolar-arterial O2 gradient (eg <15mmHg) is expected.
What is at the 3’ end of tRNA?
Transfer RNA (tRNA) is a small, noncoding form of RNA that contains chemically modified bases (eg dihydrouridine, ribothymidine, pseudouridine)
tRNA has a CCA sequence at its 3’end that is used as a recognition sequence by proteins. The 3’terminal hydroxyl group of the CCA tail serves as the amino binding site.
Elevated cholesterol concentrations increase the likelihood of?
cholesterol precipitation and gallstone formation.
High levels of bile salts and phosphatidylcholine increase cholesterol solubility and decrease the risk of gallstones
How does radiation damage DNA?
Exposure to ionizing radiation, including therapeutic and palliative radiation therapy, induces DNA damage through DNA double strand fractures and the formation of oxygen free radicals.
Metformin MOA
lowers blood glucose by reducing hepatic gluconeogenesis and increasing insulin-dependent peripheral glucose uptake.
Lactic acidosis is a rare complicaton of metformin therapy; the risk is increased in patients with underlying renal insufficiency.
What is the most important risk factor for catheter-associated urinary tract infection?
Duration of catheterization (esp >48 hour).
Prevention strategies include avoiding inappropriate catheterization (eg, placing catheter solely due to incontinence) and promptly removing the catheter when it is no longer needed.
What are signs of bulimia nervosa?
Characterized by episodes of binge eating and compensatory weight reduction behaviors.
Signs of self induced vomitting include hypokalemia, metabolic alkalosis, parotid gland enlargement, dorsal hand calluses, and dental erosion
Function of posterior cruciate ligament
Prevents posterior displacement of the tibia relative to the femur
It originates from the anterolateral surface of the medial femoral condyle and inserts into the posterior intercondylar area of the tibia.
Its integrity can be tested in the clinical setting by using the posterior drawer test
What is placenta percreta?
placental invasion through the myometrium and uterine serosa and into extrauterine structures.
An anterior placenta percreta is most likely to invade structures anterior to the uterus such as the bladder.
Function of IgA protease
IgA protease is produced by Neisseria meningitidis, N gonorrhoeae, Strep pneumoniae, and Haemophilus influenza
This enzyme cleaves secretory IgA at its hinge region, rendering it ineffective.
Secretory IgA exists on mucosal surfaces and in secretions and acts to bind and inhibit the action of pili as well as other cell surface antigens that normally mediate mucosal adherence and subsequent penetration
Side effect of isoniazid
Isoniazid is structurally similar to pyridoxine (vitamin B6) and competes for binding sites on pyridoxine-dependent enzymes. This leads to decreased synthesis of certain neurotransmitters, which may result in peripheral neuropathy.
Management involves pyridoxine supplementation
MOA of dobutamine
beta adrenergic agonist with predominant activity on beta-1 receptors
It causes an increase in heart rate and cardiac contractility, leading to an increase in myocardial oxygen consumption
What is the cause of recurrent respiratory papillomatosis?
Vertical direct transmission of human papillomavirus subtypes 6 and 11 can cause recurrent respiratory papillomatosis, which results in wart like growths most commonly on the true vocal cords
MOA of phenylephrine
Increases blood pressure via an alpha-1 receptor mediated increased in inositol triphosphate in vascular smooth muscle cells.
The abrupt increase in blood pressure triggers a reflexive increase in parasympathetic activity while decreasing sympathetic outflow.
This leads to decreased cyclic AMP activity in the heart (mediated by beta-1 adrenergic and muscarinic-2 receptors), which decreases heart rate and myocardial contractility. The reduction in heart rate is driven in part by decreased inward calcium current in sinoatrial cells
What species requires a low infectious dose to cause gastrointestinal disease?
Shigella.
The mechanism primarily involves their ability to survive in the acidic (low pH) gastric environment
Function of nuclear factor kappa B/RANK-ligand interaction
Essential for the formation and differentiation of osteoclasts.
What is osteoprotegerin?
Osteoprotegerin blocks binding of RANK-L to RANK and reduces formation of mature osteoclasts, leading to decreased bone resorption.
Denosumab is a monoclonal antibody used in the treatment of postmenopausal osteoporosis that works in a manner similar to OPG.
Chimeric antigen receptor (CAR) T cell therapy involves?
Extracting T cells from a patient with a malignancy, inserting a CAR gene against a protein overexpressed by the malignancy, and then reinfusing the modified T cells back into the patient.
CAR T cell therapy against CD19 is used to treat B cell malignancy because CD19 is expressed only by B cells
