UWorld Exam 1 Section 2 Flashcards
What vitamin B deficiency will cause neuro symptoms?
B12 - due to abnormal myelin
What is the difference between folate and B12 deficiency in clinical presentation
Both will have hematologic abnormalities (macrocytic megaloblastic anemia with hypersegmented PMNs)
Only B12 deficiency will have neuro sx
What is the defect in Myasthenia gravis?
Presentation?
Autoantibodies against post-synaptic ACh receptors
Presents with ptosis, diplopia, and weakness that worsen with muscle use
What is the defect in Lambert-Eaton myasthenic syndrome?
Presentation?
Autoantibodies against presynaptic Ca2+ channels leads to decreased ACh release
Presents with proximal muscle weakness, autonomic symptoms (dry mouth, impotence)
Symptoms improve with muscle use
What are the malignancies associated with Myasthenia gravis vs. Lambert-Eaton?
MG - Thymoma, thymic hyperplasa
Eaton-Lambert - Small cell lung cancer
Are sodium levels high or low in DKA?
Low - hyponatremia due to sodium loss via diuresis
What is the defect in Dandy-Walker malformation?
Failure of the cerebellar vermis to develop leading to cystic dilation of the 4th ventricle
What is an intraventricular hemorrhage of infants called?
Germinal matrix hemorrhage
The germinal matrix is a dense cellular and vascular layer of the subependymal zone of the brain from which neurons and glial cells develop in utero; begins to involute by 28 weeks
The germinal matrix is weak and lacking stuctural support
Hemorrhage begins between the caudate nucleus and thalamus, and the extends to lateral, third, and fourth ventricle
Patients may be asymptomatic or develop seizures, AMS, and apnea
What type of cancers are the vast majority of head and neck cancers?
And where do they tend to develop
Squamous cell
Tend to develop in the oral cavity
What is the defect in Marfan syndrome
Autosomal dominant mutation in fibrillin gene (FBN1) which codes for a proten responsible for the produciton and maintenance of elastic fibers
Describe the effects of nitrates on heart rate and end-diastolic LV volume
Nitrates lead to vasodilation
Venodilation leads to dereased venous return (decreased preload) and thus decreased end-diastolic LV volume
Nitrates can also cause arteriodilation and drop in blood pressure can lead to reflex tachycardia
Describe the different effects of CFTR and mutated CFTR on chloride channels in epithelial cells of sweat glands, respiratory, and intestines
Sweat glands:
Normal CFTR - luminal Cl- ion reabsorption and enhanced sodium reabsorption
Mutated CFTR - decreased NaCl reabsortion
Respiratory and Intestinal epithelium:
Normal CFTR - passive luminal Cl- secretion
Mutated CFTR - reduced luminal Cl- secretion and increased luminal sodium absorption (decreased water content = dehydrated, viscous mucus)
What is the defect and presentation in pseudohypoparathyroidism
Due to end-organ resistance to PTH due to defects in teh PTH receptor
Patients have hypocalcemia, hyperphosphatemia, and elevated PTH
Pseudohypoparathyroidism type 1a (Albright hereditary osteodystrophy) is an autosomal dominant disorder due to defets in GNAS1, characterized by short stature, short metacarpal and short metatarsal bones
What is the cause behind DNA loops forming when hybridized with their complementary mature mRNA?
Mature mRNAs have already had their introns spliced out
Describe the difference between allelic, genetic, and phenotypic heterogeneity
Allelic heterogeneity - different mutations at the same genetic locus cause similar phenotypes
Genetic heterogeneity - mutations of different genes cause similar phenotypes
Phenotypic heterogeneity - mutations at the same gene result in different phenotypes
What is hemochromatosis anad what are common manifestations?
Excess iron
Presentation depends on tissues involved with iron deposition:
Liver - cirrhosis
Pancreas - DM
Skin - bronze (due to hemosiderin deposition in macrophages)
Heart - arrhythmias
Testes - atrophied
What is achondroplasia and what is the mutated gene?
Most common cause of dwarfism
Autosomal dominant disorder caused by gain-of-funciton, point mutation in the fibroblast growth factor receptor 3 (FGFR3) gene
FGFR3 is normally responsible for inhibition of cartilage proliferation, particularly in the long bones - so gain-of-function would lead to restricted chondrocyte proliferation
What is the defect and presentation of maple syrup urine disease?
Defect in the branched-chain alpha-keto acid dehydrogenase complex resulting in the inability to degrade branched chain amino acids (leucine, isoleucine, and valine)
Accumulation of branched amino acids causes CNS toxicity and sweet odor in the urine
The defective enzyme requires thiamine (Vitamin B1) as a coenzyme
What is the mechanism behind seminiferous tubules maintaining higher concentrations of testosterone relative to circulation
Androgen-binding protein (ABP) within the seminiferous tubules binds testosterone and DHT to make them less lipophilic and reduce diffusion out of the luminal fluid
ABP is synthesized by Sertoli cells in response to FSH
Sertoli cell dysfunction may manifest as normal serum testosterone (hypothalamus, pituitary, and Leydig cells are fine) with low concentration of testosteron in the seminiferous tubules due to inadequate ABP production
What type of tissue is stained by red safranin O
Cartilage (Type II collagen)
What is the embryologic function of the round ligament of the uterus?
The round ligament is a vestige of the gubernaculum (ligamentous band that attaches to inferior gonad in both sexes and causes gonads to descend when it shortens)
Forms the scrotal ligament in adult males
Forms the round ligament in females (connects the uterus to the labia majora)
What is vanillylmandelic acid
The inactive breakdown product of metanephrine and normetanephrine (metabolites of epi and norepi) produced by monamine oxidase
Will be elevated in patients with a catecholamine-secreting tumor
What are the effects of a PE on pO2, pCO2, and arterial pH?
PE causes hypoxemia (low pO2)
Body tries to compensate for hypoxemia with hyperventilation and increased excretion of CO2 which causes a respiratory alkalosis (high pH and low pCO2)
