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USMLE STEP 1 - UWORLD HIGH YIELD NOTES
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USMLE STEP 1 - UWORLD HIGH YIELD NOTES
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USMLE STEP 1 - UWORLD HIGH YIELD NOTESWhat are the two major microtubular motor proteins? Which does anterograde axonal
transport, which does retrograde axonal transport? - Answers -Kinesin, Dynein
Kinesin: Anterograde
Dynein: Retrograde`
What do you think, immunologically speaking, when you see someone with recurrent
Neisseria infections? - Answers -Inability to form the membrane attack (MAC) complex
this is a common complement deficiency
What is the defect in Chronic Granulomatous disease? What is the pathophysiology? -
Answers -NADPH Oxidase deficiency leads to the inability to kill intracellular organisms
Characteristic triad of ataxia telangiectasia? - Answers -cerebellar ataxia,
telangiectasias, increased risk of sinopulmonary infections
What is the major immune deficiency of ataxia telangiectasia? - Answers -IgA
deficiency, which predisposes to infections of the upper and lower airways (and other
mucous membranes)
There's a useful mnemonic for Ataxia Telangiectasia and the gene that's mutated. What
is it? - Answers -ATM
Ataxia
Telangiectasia
Mutated
ATM gene is responsible for DNA break repair
What is one reason that lead intoxication causes hypochromic anemia? - Answers -
Mitochondrial iron transport is important for Heme synthesis! It's inhibited by lead. So
you don't make heme in your mitochondria and you get hypochromic anemia.
What is the biochemical problem in Lesch-Nyhan syndrome? (And, only if you got that
right, what are the really cool symptoms of it?) - Answers -Defective purine catabolism,
so buildup of purines. It's an X-linked recessive disorder with mutated HGPRT gene
(hypoxanthine-guanine phosphoribosyltransferase, if you want to impress people).
Now, if you got HGPRT and purine catabolism right, you can say: self-mutilating
behavior on top of mental retardation, choreoathetoid (think Chorea) movements and
spasticity.
What is the defect in Niemann-Pick disease?
What causes that?
,What is the common macular finding? - Answers -Sphingolipid degradation is defective
Caused by an autosomal recessive defect in sphingomyelinase
Cherry Spot on the macula? Niemann Pick's or Tay Sach's.
If a baby gets exposed to an unclean knife (...) and subsequently develops rigid
paralysis, what is the diagnosis, where do we think this might happen, and how do we
prevent it? - Answers -Neonatal Tetanus
Developing Countries
Maternal immunization with tetanus toxoid is the best way to prevent it
an adeuately immunized mom will transfer IgG's across the placenta to the neonate
Which microtubule associated protein aids in anterograde transport of intracellular
vesicles and organelles? Which end of the microtubule do they go towards? - Answers -
Kinesin.
Towards the (+) rapidly growing end.
What is an early BRAIN finding of Ataxia-Telangiectasia and how does it manifest itself?
- Answers -Cerebellar atrophy
manifests as ataxia in the first years of life.
High yield path association for Alzheimer's disease? - Answers -Neurofibrillary tangles
in the neocortex
High yield path association for Parkinson's disease? - Answers -Loss of neurons in the
substantia nigra
High yield path association for Huntington disease? - Answers -Atrophy of caudate
nucleus
What are the major manifestations of Ataxia-telangiectasia? - Answers -cerebellar
ataxia, oculocutaneous tenlangiectasias, repeated sinopulmonary infections, and an
increased incidence of malignancy
If you heard: amenorrhea, bitemporal hemianopsia, and enlargement of the pituitary
gland on brain imaging, what would you be thinking? - Answers -Prolactinoma, the most
common pituitary adenoma.
What embryological layer is the anterior pituitary derived from? - Answers -Surface
ectoderm
What is the most common congenital abnormality associated with the use of Sodium
Valproate during pregnancy? - Answers -neural tube defects, e.g., meningocele
,because valproate inhibits intestinal folic acid absorption resulting in teratogenicity
What is the characteristic histology of a craniopharyngioma? - Answers -On light
microscopy, cysts are lined by stratified squamous epithelium, possibly with Keratin
perals. Cysts are usually filled iwth a yellow, viscous fluid that's rich in cholesterol
crystals.
Where do craniopharyngyomas arise from? - Answers -Craniopharyngiomas are
calcified cystic tumors that arise from remnants of Rathke's pouch (embryonic precuros
of the anterior pituitary)
What equation helps us prove the following condition: to maintain a constant fluid flow
througha tube with varying diametes, how are cross-sectional area and flow velocities
related? - Answers -Volume in must equal volume out, right? Vol(in) = A1 * V1 ; Vol(out)
= A2*V2
So any rearrangement of that equation holds true in a physiological system.
A2 = A1*V1 / V2 for example, works.
This applies for blood flow in the cardiovascular system.
What do you think when you hear a patient who has a heart murmur presenting with the
following physical exam findings:
Bounding femoral pulses, carotid pulsations accompanied by head-bobbing. - Answers -
Aortic Regurgitation
How does the pathophysiology of aortic regurgitation explain the characteristic findings
of these patients? And what are those findings again (2 major ones)? - Answers -(1)
Bounding femoral pulses;
(2) Carotid Pulsations with head-bobbing (de Musset sign)
There is a large LVSV, a large regurgitant SV, and a large pulse pressure.
Bounding femoeral and carotid pulses marked by abrupt distention and quick collapse
("water hammer" pulses) are the result of large pulse pressure
the head bobbing is due to the transfer of mementum from htel arge left ventricular
stroke volume to the head and neck
What is the order of cardiac tissue conduction velocity from *fastest* to *slowest*? -
Answers -Purkinje System
Atrial Muscle
Ventricular Muscle
AV node
, What is the mnemonic to help you remember the order of cardiac tissue conduction
velocity? - Answers -P ark (purkinje's)
AT (atria)
VENT ura (ventricles)
AV enue (AV node)
Where does Atrial Natriuretic Peptide (ANP) come from? In response to what? -
Answers -Atrial Cardiomyocytes in response to atrial stretch, it is a signifier of volume
expansion
What is the ultimate action of ANP? - Answers -Lowers blood pressure through
peripheral vasodilation, natriuresis, and diuresis.
How does ANP affect the following organs:
(1) kidney?
(2) adrenal gland?
(3) blood vessels? - Answers -(1) Dilates the afferent arterioles, increasing GFR and
urinary excretion of sodium and water (diuresis); also limits sodium reabsorption (in
proximal tubule) and inhibits renin secretion
(2) restricts aldosterone secretion --> increase in sodium and water excretion by the
kidneys
(3) relaxes vascular smooth mucles, producing vasodilation; also increases capillary
permeability, leading to fluid extravasation to the interstitium and a decrease in
circulating blood volume
What major hormone comes from the renal juxtaglomerular cells, and what is its net
effect on the vasculature? - Answers -Renin, which catalyzes angiotensinogen --> ang I
angiotensin causes vasoconstriction, increased blood pressure, and aldosterone
release
What is the pathophysiology of CHF in general terms? - Answers -CHF occurs when the
heart is unable to pump sufficient amounts of blood to meet body's metabolic demands
How is the reduced cardiac output in CHF initially detected? How does the body attempt
to compensate? - Answers -A drop in blood pressure
Compensatory neurohormonal stimulation that is directed at maintaining blood pressure
and tissue perfusion
Chiefly mediated through:
(1)increased sympathetic nervous system activity,
(2)stimulation of the renin-angiotensin-aldosterone pathway,
(3) release of ADH
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