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Usmle > Block 32 > Flashcards

Block 32 Flashcards

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USMLE® Step 1 flashcards
1
Q

Anticholenrgic toxicity

A 
Clincal : -fever
-flushing
-dry skin and mucus membrane
- non reactive mydriasis
- delerium
Urinary retention 
-decreased bowel sounds
-tachycardia
Causes: 
1. Antihistamines
2. TCA
3. 1st generation antipsychotic (chlorprozamine)
4. 2nd generation antipsychotic (clozepine) 
5. Anti parkinson drugs (benzotropine, trihexyphendyl)
6. Belladonna alkaloids (atropine)
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2
Q

Epinephrine effect on vessels

A
  • On low doses the ß2 mediated vasodilation predominates whereas at high doses å1 induced vasoconstriction is more pronounced.
  • if ß2 is blocked, (by propronalol for example), the å1 effect will be minimal, however if an epinephrine is infused the å1 effect will predominates leading to increase in BP with decrease in HR due to proponalol effect on ß1.
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3
Q

Hemodynamic effect of epinephrine

A
  1. HR and contractiliy : increases them (ß1 effect)
  2. Systolic BP: increase (using ß1 +å1)
  3. Diastolic BP: decrease at low dose(ß2>å1)
    Increase at high doses (å1>ß2)
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4
Q

Trendelenberg gait is seen in injury to which nerve

A

-superior gluteal nerve

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5
Q

In response of ADH where is the lowest osmolarity present

A

(Lowest osmolarity = diluted urine)
-distal convulated tubule is imperable for water —> it leads to absorption of solutes thus diluting the urine (lowest osmolarity)

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6
Q

Bacillus anthrax toxin mechanism

A

Anthrax exotoxin composed of pretective antigen, edema factor and lethal factor.
-protective agent translocase the EF,and LF into the cell.once inside the cell EF acts as calmodulin dependent adenylate cyclase that increase cAMP concentration. It causes accumulation of fluid within and between cells and also results in suppression of neutrophil and Macrophages function.

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7
Q

Micturition regulation

A
  1. Sacral micturition center (located in S2-S4) (bladder contraction)
  2. Pontine micturition center - located on pontine reticular formation
  3. Cerberal cortex - inhibit sacral micturition center.
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8
Q

Acute retinal hemorrhage

A
  • most commonly caused by sever poorly controlled hypertension.
  • hypertensive retinal hemorrhae typically causes painless, unilateral visual disturbances, ranging from mild obscuration without loss of visual acuity to permanent blindness.
  • severe HTA in retinal precapillary arterioles causes endothelial disruption, leakage of plasma into the arteriolar wall, and fibrinous necrosis.
  • necrotic vessels can then bleed into the nerve fiber layers, causing dot and flame shaped hemorrhages.
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9
Q

CD 31 expressing tumor associated with arsenic exposure or polyvinyl chloride

A

Liver angiosarcoma

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10
Q

Rapid urease test used to diagnose

A

H.pylori
-h.pylori produces large amounts of extracellular urease enzyme hence the use of urea solution for this test.
-urease converts urea to carbon dioxide and ammonia, causing PH increase and change in the color to pink (alkaline).
Alkaline color for more than 5 minutes indicates positive diagnosis.

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11
Q

ETEC

A
  • travelers diarrhea, gram negative cholera like toxin

- watery diarrhea with abdominal cramping, nausea and vomiting and possibly low fever.

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12
Q

How to reduce the risk of transmission of microorganisms between patients

A
  • hand hygiene by health care workers is the single most important measure.
  • it includes hand-washing with soap and water or using alcohol based hand sanitizers that dont require water.
  • proper hand-washing technique involves washing all surfaces of the hands and fingers with soap and water for at least 15 seconds, drying with a disposable towel, and using the towel to turn off the faucet.
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13
Q

Shigella binding site in intestine

A
  • Sihgella cant bind all intestinal cells, shigella exhibits specificity for the microfold cells at the vase of mucosal villi within a peyer patch region of the ileal mucosa.
  • shigella penetrates the mucous membrane by passing through M cells via endocytosis. It subsequently lyses the endosome, multiple, and spreads laterally into other epithelial cells.
  • this result in denuing and ulceration f the mucosa and subsequent leakage of blodd, inflammatory elements, and mucus into the intestinal lumen.
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14
Q

Blunt trauma to the eye

A
  • causes rapid increase in pressure that typically doesn’t rupture the globe but it transmitted posteropry into the orbit.
  • the weakest plates of bone in the orbit, the medial and inferior walls , are common site of fracture
  • fracture is typically evident on radiographic imaging and fluid or herniation of the orbital content can often visualized in the adjacent normally air filled sinuses.
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15
Q

Infundibulopelvic ligament

Ovarian torsion

A
  • its also called suspensory ligament of the ovary, it also houses the ovarian nerve plexus . Rotation of the ovary around the IP ligament leads in ovarian torsion.
  • the main risk factor for torsion is the presence of large ovarian mass, the weight of the mass causes ovary to twist and occlude the ovarian vessel and nerve.
  • a patient with ovarian torsion will typically present with sudden onset unilateral pelvic pain and nausea and sometimes vomiting and fever.
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16
Q

Cavernous hemangioma

A
  • the most common benign liver cancer typically present in adults 30-50 years of age.
  • these benign tumors are thought to be congenital malformation that enlarge by ectasia, not hyperplasia or hypertrophy.
  • multiple, well circumscribed, less than 5 cm in width
  • these tumors consist of cavernous blood filled vascular spaces of variable size lined by a single layer of epithelium.
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17
Q

Hepatic adenoma can regress in case of

A

-stopping oral contraceptive.

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18
Q

Polyomyositis

A

-symmetric proximal muscle weakness
-increasing difficulty climbing stares, getting up from chair and carrying heavy objects
- elevated CK, aldolase
-autoantibodies (ANA, Anti jo1, anti histidyl tRNA synthetase)
- endomysial mononuclear infiltrates and patchy necrosis
Associated complication:
- interstitial lung disease and myocarditis.

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19
Q

Acute interstitial nephritis(AIN)

A
  • fever, rash, and AKI occuring within a few weeks of starting ß lactam is highly suggestive of acute interstital nephritis.
  • other medication usually (NSAID, sulfonamides, rifampin and diuretics).
  • AIN is thought to be mediated by IgE mediated hypersensetivity or cell mediated reaction (IV H.S).
  • it leads to interstitial edema, leukocytes infiltration.
  • inflammatory cells commonly infiltrates the tubular epithelium and granuloma formation may be observed.
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20
Q

Disease calculation for a child to born with recessive disorder

A

P(affected child) = 1/4 X P (carrier mother ) X P (carrier father)
This is done in case the question doesnt state if the father and mother are true carriers.

21
Q

Pathogenesis of cholesterol gallstones

A
  • in the liver free cholesterol is converted into cholic acid and chenodeoxycholic acids through a series of chemical reaction begining with cholesterol 7a hydroxylase.
  • as water insoluble cholesterol is secreted in bile , it is rendered soluble in small amonts by detergent action of hydrophobic and hydrophilic bile salt, and phosphatidycholine (phospholipid). When these can be made soluble it precipitates into crystals that eventually merge and form gallstones
22
Q

Decreased levels of phosphatidylchline leads to

A

Gall stones formation

It can be given to a patient with gallstones to help dissolve gallstones.

23
Q

Tolerance to opioids

A

Tolerance to opioid usually expected to occur however tolerance to constipation and miosis doesn’t readily occur and constipation is the most common and persistent side effect of opioid.

  • opioid stimulate mu receptors in GI tract causing decrease in secretion and gastric motility.
  • pts treated with opioid should recieve prophylactic bowel regimen (high fibers diet, laxative and increased fluid)
24
Q

Sorolimus

Rituximab

A
  1. Sorolimus mechanism of action: proliferation signal inhibitor by targeting mTOR signaling pathway, it binds to immunophilin FK-506 binding protein, forming complex that inhibits mTOR —> interruption of IL-2 signal transduction.
  2. Rituximab: antibody against CD20 antigen, it depletes B cells through multiple pathways including complement mediated lysis, antibody- dependent cytotoxicity, and induction of lymphocytes apoptosis
25
Q

Mucormycosis

A
  • most cases are rhinocerberal.
  • infection acquired through nasal passage to the sinuses/orbits and then sometimes the brain, leading to confusion neurological deficit and death.
  • black necrotic eschar in nasal cavity is characteristic
  • its diagnosed using mucosal biopsy to check for nonseptate hyphae with right angle branching.
26
Q

Types of xanthomas

A

Usually are 5

  1. Eruptive xanthoma- appear with increased plasma triglycerides and lipid
  2. Tuberous and tendenious xantoma - achilles tenon and extensor tendonds of the fingers.
  3. Plane xanthomas - linear lesion associated with PBC
  4. Xanthelasma - soft eyelid or periorbital plaque with no associated lipid abnormalities in 50% of cases.
27
Q

Penetrating injury at the left sternal border in the fourth intercostal space will injure ?

A

-right ventricle due to the fact that it composes the majority of the anterior surface of the heart

28
Q

Nasal injury

A

Nasal mucosa is highly vascular and easily irritated by trauma (eg nose picking), mucosal dryness and rhinitis.

  • epistaxis is very common in children and may be classified anterior or posterior.
  • anterior nosebleed is more common and vast majority occurs within the watershed area in the nasal septum known as hesselbach plexus.
  • managment to stop bleeding is usually by direct compression of the nasal alae.
  • cautery (silver nitrates ) may be necessary in persistant bleeding.
29
Q

Proliferative phase vs secretory phase

A
  1. proliferative phase is characterized by increased levels of E2 -> nonbranching, nonbudding uniform glands evenly distributed,
    - in midproliferative the glands are tubular ,narrow and lined with pseudostratified elongated mitotically active epithelial cells.
    - the stratum functionale contains compact nonedematous stroma.
  2. Secretory phase is characterized by —> increase PR —>follow ovulation —> development of secretory endometrium with large glands —> coiled and cell aquire large cytoplasmic vacules
    - glyocgen rich mucus is released into glandular lumens.
30
Q

Autosomal recessive polycystic kidney disease

A 
Caused by mutation in PKHD1 gene, codes for fibrocystin (liver and kidney) 
Clinical findings: 
- renal insuffeciency 
-nephromegaly
-hypertension( after few months )
-respiratory distress at delivery
-oligohydroamnios — potter sequence
31
Q

Antigenic variation

A

This is especially seen in reinfection, as the body develops humoral immunity against one strain, the reinfectant strain will have another proporties due to recombination of pilus proteins —> produce new antigenic types of pilli

32
Q

Malignancy presence along with nephrotic syndrome suggests

A
  • membrenous glomerulopathy
  • biopsy shows uniform, thickening of glomelular capillary wall on light microscopy without an increase in cellularity. IF reveals granular deposits and EM shows thickining by irregular dense deposits between basment membrane and epethilal cells that resembles spikes.
  • its caused by :
    1. Systemic disease (D.M, SLE. solid tumors).
    2. Certain drugs such as gold, penicillamine and NSAID
    3. Infections - hepatitis B, hepatitis C, malaria, and syphillis
33
Q

Familial dysbetalipoproteinemia

A
  • its charactrized by xanthomas and premature CHD.
  • AR disorder that is clinically more sever in pts with other condition affecting lpoprotein metabolism (e.g D.M)
  • the primary defect in this disorder are in ApoE3 and ApoE4 apolipoproteins found on the TAG rich lipoproteins (chylomicrons and VLDLs) that are responsible for binding hepatic apolipoprotein receptors.
  • without ApoE3 and ApoE4, the liver cant efficiently remove chylomicrons and VLDL remenants from circulation, causing their accumulation in the blood —> increased TAG and cholesterol.
34
Q

Familial chylomicronemia syndrome

A

LPL defeciency as well as ApoC2
Leads to elevated chylomicrons, and TAG.
-may lead to acute pancreatitis and lipemia retinalis.

35
Q

Anicteric viral hepatitis

A

In children age <6 , HAV infection is most often (.80%) silent or subclinical (anicteric ). Less frequently it can present as acute self limited illness .

  • clinical disease is typically more severe in adults (some of them develop an aversion to smoking for unclear reasons)
  • hepatitis A rarely lead to liver failure
36
Q

Acyclovir nephrotoxicity

A
  • phenomenon that occur in 5-10% of patients
  • when acyclovir concentration in collecting ducts exceeds its solubility crystalization, crystalluria and renal tubular damage may result.
  • in most cases, this toxic complication is transient and can be prevented with adequate hydration and dose adjusment.
37
Q

Allupurinol in leukemia and lymphoma

A

-it can be used to prevent tumor lysis associated urate crystal nephropathy

38
Q

Low molecular weight heparin mechanism of action

A
  • administration of heparin increases the effect of the naturally occuring anticoagulant antithrombin III, it binds to AT III via pentasaccharide in the heparin chain, this result in a conformational change of AT III which subsequently inhibits factor Xa and neutralized thrombin, promoting anticoagulation.
  • AT III activated by LMWH acts predominantely at factor Xa (not thrombin …… not thrombin … not thrombin ) (thrombin is by unfractionated heparin)
39
Q

Cardiac output equations

A

CO=SV X HR

CO= rate of O2 consumption / arteriovenous O2 content differences

40
Q

Beta blockade on heart failure

A
  • decrease myocardial work and O2 consumption —> slowing ventricular rate and reducing contractility.
  • lowers peripheral resistance by decreasing circulating levels of vasoconstricting hormones.
  • These effects are cardioprotective and help reduce cardiomyocyte death and limit deleterious cardiac remodeling.
41
Q

What is used to prevent PE

A

Low dose heparin

42
Q

Why does hemorrhagic infarct occur from PE

A

Because the lung have dual blood supply drom both pulmonary and bronchial arteries, bronchial blood usually hemorrhages into the ischemia area causing ,red hemorrhagic infarct.
Occlusion of the peripheral branch of pulmonary artery produces a wedge shaped peripheral infarct adjacent to the pleura.

43
Q

Rectal biopsy in hirschprung disease should be taken from

A

The area with narrow lumen (not the megacolon part) from the submucosa as they contain the meissner and myenteric plexi

44
Q

Lesion to temporal love (vision problems)

A

-lesions in temporal lobe can disrupt meyers loop and produce controlateral superior quadrantnopia, temporal lobe lesions can also produce other neurologic manifestation including aphasia, memory deficits, seizures and hallucinations

45
Q

In gluconeogenesis phosphophenolpyruvate requires what in order to be converted from oxaloacetate

A

GTP that is obtained from the conversion of succinyl-coa to succinate.

46
Q

Pyruvate metabolism under hypoxic conditions

A

Under hypoxic condition, Intracellular accumulation of NADH inhibits pyruvate dehydrogenease. As a result increased amounts of pyruvate is shifted toward lactate dehydrogenease. Which regenerates NAD+ from NADH.

47
Q

Pyruvate enzymes

A
  1. Pyruvate kinase : PEP —> pyruvate
  2. Pyruvate carboxylase : pyruvate —> oxaloacetate
  3. Pyruvate dehydrogenase -> pyruvate -> actyl-coa
48
Q

Endotoxin creates its effect by binding

A

TNF-å, IL-1 and IL-6.

Usmle (45 decks)

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