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USMLE Step 1 Flash Cards > Phisiology > Flashcards

Phisiology Flashcards

1
Q

Why low estrogen state (postmenopausal, ovary dysfunction or surgical remove) favors development of osteoporosis?

A

⬇️ Estrogen ▶️ ⬇️ Osteoprotegerin ⬆️ RANK-L ▶️ (+) differentiation to active osteoclasts ▶️ bone resorption
⬇️ Estrogen ▶️ ⬆️ RANK in osteoclasts precursors

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2
Q

Pulmonary function test pattern in pulmonary fibrosis.

A
  • Restrictive pattern: ⬇️ lung volumes
    ⬇️ FEV1, FVC
    Normal or ⬆️ FEV1/FVC ratio
    ⬇️ Diffusion capacity (DLCO)
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3
Q

Excess copper (from senescence ceruloplasmin and not absorbed) is mainly excreted by which pathway?

A

Secreted into bile ▶️ excreted in stools

-Renal tubular secretion ▶️ 5-15% of excretion

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4
Q

Which component of surfactant rises in amniotic fluid at week 36 and which at week 30?

A
  • Phosphatidylglycerol ▶️ 36 week

- Phosphatidylcholine (lecithin) ▶️ 30 week

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5
Q

Where is controlled the respiratory rate? How is it regulated based on oxygen content?

A

Medullary respiratory center based on input from:

  • central chemoreceptors (medulla) ▶️ PaCO2 (mainly in healthy)
  • peripheral chemoreceptors (carotid and aortic bodies) ▶️ PaO2 (mainly in severe hypoxia)
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6
Q

In a water deprivation state (ex, dehydration) which portion of the nephron has the most concentrated and the most diluted urine? why?

A
  • Water deprivation state = ↑ADH levels →↑aquaporin-2 in principal cells at Collector ducts (V2R)→↑H2O reabsorption→most concentrated urine
  • Ascending loop of Henle→↑NaCl reabsorption→dilution
  • Distal convoluted tubule most diluted urine (even more reabsorption of electrolytes, impermeable to water - lowest osmolarity [hypotonic] - regardless ADH levels)
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7
Q

What is the Jervel and Lange-Nielsen syndrome? why does it occur?

A
  • Sensorineural hearing loss and congenital QT long syndrome
  • Mutations (autosomal recessive) - KCNQ1, KCNE1 genes (voltage-gated K+ channels)→↓ K+ current→↑ action potential and QT duration.
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8
Q

Cause and ECG changes of Brugada syndrome.

A
  • Mutations in cardiac sodium or L-type clacium channels
  • pseudo right bundle branch block. ST-segment elevation V1-V3

*↑Risk ventricular tachyarrhythmias and sudden death

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9
Q

Which volumes are elevated in COPD patient, mainly in emphysema?

A
  • Residual volume
  • Functional Residual Capacity
  • Total Lung Capacity
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10
Q

Differences between myoglobin and hemoglobin respect O2-Hb dissociation curve and affinity.

A
  • Myoglobin ▶️ ⬆️ affinity O2 ▶️ hyperbolic curve (P50=1 mmHg)
  • Hb ▶️ less afinity than myoglobin (Affinity ⬆️ after binding of 1 O2 molecule heme-heme interaction) ▶️ sigmoid curve (P50=26mmHg)

*myoglobin is equivalent to a 1 subunit (alpha or beta) of the Hb

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11
Q

What is the mechanism by which CO poisoning causes headache, dizziness, seizures, respiratory arrest?

A

Competitive binding to Hb and with 200x greater affinity than O2

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12
Q

Why stimulation of B1 adrenergic receptor (mainly ⬆️ the heart rate) affect systolic blood pressure? what is the effect?

A

➕B1 ▶️ ⬆️ HR and contractility ⏩ BP=CO(cardiac output)xHR ▶️ ⬆️ BP (mainly systolic)

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13
Q

Which protein allows the transport of neurotransmitter-containing secretory vesicles in the neurons?

A

Kinesin ▶️ microtubule-associated, ATP-powered motor protein ▶️ anterograde transport down axons to synaptic terminals

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14
Q

Why is less the ventilation at the apex of the lungs?

A

Gravity stretch downward the lungs from the apex - apex is fixed in pleural cavity by low intrapleural pressure (“pleural suction”) ▶️ Alveoli more stretched and expanded at apex than base during end-expiration ▶️ less air during inspiration (less compliance)

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15
Q

Why if ventilation and perfusion increases from apex to the base, the V/Q (ventilation/perfusion) ratio is greater in apex than base?

A

Perfusion (Q) ⬆️⬆️ > Ventilation (V) ⬆️

*“denominator is much greater and numerator is slighty increased in base”

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16
Q

Which are the changes on GFR, FF and RPF if selectively constrict efferent arteriole and afferent arteriole?

A
  • Efferent arteriole constriction ▶️ ⬇️ glomerular blood outflow ▶️ ⬆️ glomerular capillary hydrostatic pressure ▶️ ⬆️ GFR; ⬇️ RPF (stasis) ⏩ FF=GFR⬆️/⬇️RPF=⬆️FF;
  • If Efferent arteriole constriction continues ⬆️⬆️ ▶️ ⬆️ oncotic pressure more than hydrostatic in glomerulus ⏩ ⬇️ GFR
  • Afferent arteriole constriction ▶️ ⬇️ plasma flow into glomerular capillaries ▶️ ⬇️ capillary hydrostatic pressure ▶️ ⬇️ GFR; ⬇️ RPF equal than GFR ⏩ FF unchanged
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17
Q

What happen when muscle make too much force, and what mediates that response?

A

Golgi tendous organ (GTO)▶️ interneuron ▶️ 🚫 alpha-motoneuron in spinal cord ⏩ sudden muscle relaxation

*GTO response to actively contraction of muscle to maintain muscle tension

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18
Q

Which regions of the sarcomere have only thick and only thin filaments? Which bands remain unchanged and which changes in length during contraction?

A
  • Thick filaments (myosin) ▶️ band H
  • Thin filaments (actin) ▶️ band I
  • During contraction ▶️ band A not change, band I, H get shorter
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19
Q

Why during panic attack a patient can have drowsiness, dizziness, blurred vision, weakness (neurologic symptoms)?

A

Panic attack ▶️ hyperventilation ▶️ ⬇️ PaCO2 ▶️ hypocapnia ▶️ brain blodd vessel constriction (⬆️resistance) ▶️ ⬇️ cerebral blood flow

*CO2 ▶️ potent cerebral vasodilator (most powerful effect of the arterial blood gases on brain blood flow). PaO2<50mmHg (severe hypoxia) ▶️ vasodilation in brain vessels ▶️ ⬆️ cerebral blood flow and intracranial pressure

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20
Q

Which vitamins are lack in the newborn and must be supplemented and why?

A
  • Vitamin K ▶️ immediately parenteral at delivery ▶️ prevent hemorrhagic disease of the newborn
  • Vitamin D in exclusively breastfed, lack sunlight exposure, dark skin pigmentation ▶️prevent rickets

*Iron in preterm/low birthweight, breastfed >4 mo until initiate solid food

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21
Q

Which substances in excess can increase the resistance to insulin during pregnancy?

A
  • Plancental growth hormone (PGH)→Placental maturation
  • human Placental lactogen (hPL)→Fetal development
  • TNF-­­α, leptin, adiponectin
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22
Q

What part of cardiac cycle is the sarcomere length of the left ventricular muscle fibers the greatest and the lowest?

A
  • End diastolic volume→longest sarcomere length

- End systolic volume→shortest sarcomere length

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23
Q

When occur an intrapulmonary shunt?

A

When there is an area adequately perfused but poorly ventilated

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24
Q

What substances predominantly drive the angiogenesis?

A
  • Vascular endothelial growth factor (VEGF)

- Fibroblast growth factor (FGF)

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25
Q

What is the approximate intrapleural pressure value at the functional residual capacity (FRC) point? Why?

A
  • -5 mmHg
  • Tendencies of chest wall to expand and lung to collapse oppose one another
  • FRC point ▶️ positive alveolar transmural pressure and negative chest wall transmural pressure oppose one another equally ▶️ airway pressure of zero (different of intrapleural pressure) ▶️ no tendency of air to flow into or out the lungs ⏩ center of the airway pressure-volume curve
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26
Q

Where is the first site of electric activation of the heart?

A

Sinoatrial node (dominant pacemaker) ▶️ junction of the right atrium and superior vena cava

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27
Q

Which study can you order in a patient that suspect pulmonary embolism but has a contraindication to use contrast? What would be the result?

A
  • Contrast contraindication ▶️ can not make CT angiography
  • Ventilation/perfusion scan (V/Q) ▶️ area of perfusion defect without ventilation defect (mismatched perfusion defect) ⏩ V/Q mismatch
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28
Q

What wave of the jugular venous tracing is absent in atrial fibrilation? why? and when this wave can be prominent?

A
  • a wave→atrial contraction
  • A fib→no atrial contraction, no p wave on ECG, it is “fibrilating”
  • Hypertrophic cardiomyopathy
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29
Q

Transient holosystolic murmur in a patient with congestive heart failure, dissapear with treatment.

A

Functional mitral regurgitation

  • ↑Preload→Acute dilatation of LV→separate normal mitral valve leaflets
  • Tx→↓preload and afterload
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30
Q

Why mature RBC can not synthesize Heme, even though they have cytoplasmic enzymes involved in Heme synthesis?

A
  • Normally lack of Mitochondria→need to first and final 3 steps of Heme synthesis→no Heme→no Hb.
  • Heme synthesis (every organ, but mainly)→RBC precursors in BM, hepatocytes (microsomal cytochrome P450)

*Mature RBCs don’t synthesize Hb, survive for 120 days

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31
Q

Functions of von Willebrand factor (vWF).

A
  • Endothelial damage→vWF binds glycoprotein Ib receptors (GpIb) on platelet→platelet aggregation and adhesion to subendothelial collagen
  • Carrier for factor VIII→prolongs its half-life
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32
Q

Effect of the vasopressin on urea clearance.

A
  • Vasopressin→(+)V2 receptors in collecting ducts→↑permeability of urea in medullary collecting ducts→↓urea clearance
  • Passive reabsorption of urea into medullary interstitium→↑medullary osmotic gradient→maximally concentrated urine
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33
Q

At which point of the lung volumes we find the lowest pulmonary vascular resistance, and why?

A

FRC→point when don’t have maximal expiration nor maximal inspiration→equilibrium point

  • Maximal inspiration→expand alveoli→↑length, ↓diameter of alverolar vessels→ collapse the alveolar blood vessels→↑alveolar vessel resistance
  • Maximal expiration→↓lung volumes→↓radial traction, ↑compression by positive intrathoracic pressure on extra-alveolar veins and arteries→narrow extra-alveolar blood vessels→↑extra-alveolar vessel resistance
34
Q

Source and effect of secretin at the pancreas.

A
  • S cells of duodenum→in response to ↑H+ duodenal due acidic gastric contents arriving→Secretin→(+) pancreatic ductal cells→↑HCO3, ↓Cl in pancreatic secretions (exchange for one another at the apical surfaces of pancreatic ductal cells), Na, K remains equal.
35
Q

What is the fastest and slowest cardiac tissue conduction?

A
  • Fastest→Purkinje fibers
  • Slowest→AV node

*Atrial muscle is faster than ventricular muscle

36
Q

Concentration of PAH is lowest in what segment of the nephron?

A

Bowman’s space

*Primarily secreted in proximal tubule, freely filtered by glomerulus, no reabsorbed

37
Q

In proximal tubule what substances are in high, equal and low concentrations in the tubular fluid and why?

A

In descendent order

  • ⬆️concentration▶️PAH (90% secreted), Inulin, creatinine (20% secreted), urea▶️poorly reabsorbed, active secreted, freely filtered
  • “Equal” or minimum change▶️Na, K (reflecxt osmolarity of tubular fluid)▶️equal reabsorption with the water
  • ⬇️concentration▶️bicarbonate, Amino acids, glucose
38
Q

Function and location of enteropeptidase

A

Jejunal brush border enzyme►trypsinogen→trypsin

39
Q

In what portion of the nephron is the highest and lowest osmolarity in absence of ADH?

A
  • Descending limb of loop of henle→permeable to water but not solutes►more hypertonic tubular fluid
  • Thin and thick ascending limb of henle→impermeable to water►passive absorption of NaCl (thin) and active transport out of the lumen by Na/K/Cl cotransporter (thick)→↓osmolarity, formation of corticomedullary concentration gradient

*Collecting ducts→permeability to water depends of ADH→water impermeable and absorbs more solutes if ↓ADH►hypotonic tubular fluid

40
Q

Changes of arterial and venous pH, pO2, pCO2 during moderate (aerobic) exercise?

*Change of arterial pH during strenuous exercise.

A
  • Arterial▶️near normal resting values▶️⬆️O2 consumption and CO2 production▶️equilibrated▶️⬆️cardiac output/skeletal muscle perfusion ventilation
  • Venous▶️⬆️O2 extraction, ⬆️CO2 production⏩⬇️pH, ⬇️pO2, ⬆️pCO2

*Lactic acidosis▶️⬇️arterial pH

41
Q

Effect of epinephrine on Beta cell of pancreatic islets and insulin secretion

A
  • Alpha-2 adrenergic receptor→↓insulin→predominates

- Beta-2 adrenergic receptor→↑insulin

42
Q

Which molecule interact with K channel at beta pancreatic cell to regulate insulin secretion? How is the regulation?

A

Glucose▶️glycolysis▶️⬆️ATP▶️binds and close K channel▶️depolarization▶️open voltage-dependent Ca channel▶️⬆️intraceullar Ca▶️insulin secretion

43
Q

What cells secretes a substance that control the storage and release of iron by other cells?

A

Hepatic parenchyma cells▶️hepcidin (acute phase reactant)▶️bind ferroportin (transport intracellular Fe to circulation)▶️internalize and degrade

  • Inflammation and ⬆️Fe▶️⬆️Hepcidin
  • Hypoxia▶️erythropoiesis▶️⬇️Hepcidin▶️favors Fe absorption and accumulation in the body (Fe release by M🚫)
44
Q

Which are the most important acid buffers in urine during metabolic acidosis and do they allow?

A

-NH3▶️trap H+▶️NH4 (most important - kidney ⬆️⬆️

45
Q

Effect of CO poisoning on Hb, SatO2, PaO2, O2 content and methemoglobin.

A

No effect on PaO2 (amount of O2 dissolved in plasma), ↓SatO2, ↓O2 content, ↑carboxyhemoglobin, No methemoglobin

46
Q

Causes of methemoglobin formation

A
  • Nitrites→dietary intake, or polluted/high altitude H2O
  • Benzocaine poisoning

*Oxidizing Fe2+ (normally in Hb)→Fe3+►does not bind O2 as readily, ↑affinity for cyanide.

47
Q

If fertilization and implantation occur, when would be detected the B-hCG first in serum?

A

8 days after fertilization

*Urinary B-hCG is detected at 14 days after fertilization

48
Q

What substance can be used as a marker of osteoblasts activity?

A

Serum level of bone specific alkaline phosphatase

*Differentiated by electrophoresis, specific monoclonal antibodies, heat desaturation (ex, bone specific easy desaturated by heat)

49
Q

Uses and source of calcitonin

A
  • Marker for medullary thyroid cancer▶️produced by parafollicular C cells of thyroid gland
  • Tx of hypercalcemia
50
Q

Most commonly method used to assess osteoclast activity

A

Deoxypyridinoline urinary excretion▶️pyridinoline covalently cross-link collagen fibers

51
Q

In the setting of water deprivation (high ADH serum level) which segment of the nephron allow absorption of specific solute that is very important to the high medullary concentration gradient?

A

ADH▶️⬆️H2O reabsorption in medullary collecting ducts▶️conentrate urine in duct▶️⬆️⬆️urea▶️⬆️passive urea transporters▶️urea pass down gradient to medullary interstitium and thin loop of henle⏩50% of the medullary Osm

52
Q

Principal autoregulation of coronary blood flow

A
  • Adenosine▶️vasodilator in small coronary arterioles

- Nitric Oxide (NO)▶️coronary vascular dilation in large arteries and pre-arteriolar vessels

53
Q

Cause of secondary polycythemia and increase hematocrit in obstructive sleep apnea. What others disease may be associated?

A
  • Peritubular renal cells in renal cortex sense hypoxia▶️⬆️Erythropoeitin▶️⬆️RBC by bone marrow
  • COPD, Right-left shunt, high altitude
54
Q

Which type of RBC do you expect to find in a blood smear of a patient with iron supplementation by iron deficiency anemia? Why do they have that aspect?

A
  • ↑Iron→↑Hb→↑erythropoiesis→↑both mature RBC and retyculocytes (immature RBC)
  • Retyculocytes→↑ribosomal RNA (basophilic, reticular) [lack nucleus]►Blue and large in Wright-giemsa stain
55
Q

What hormone stimulates the bicarbonate rich and chloride poor fluid secretion from pancreas, which cells produce it, its function and main stimulus?

A
  • Duodenal mucosa→Intestinal S cells→Secretin►neutralizes hydrochloric acid from gastric contents
  • Secretion begin with duodenal pH<5, rises with pH<3
56
Q

What is the effect of the demyelination on the signal tansmission?

A
  • Decrease lenght constant (space constant - How far along an axon an electrical impulse can propagate)→impaired stimulus transmission
  • Increase time constant→slower impulse conduction
57
Q

What is the function of myelin?

A
  • ↑Membrane resistance→↓charge dissipation→↑Length constant→more effective transmission (insulation)
  • ↓Membrane capacitance→↓Time constant→↑axonal conduction speed
58
Q

What is the length constant and time constant of the signal neuronal transmission?

A
  • Length constant→how far along an axon an electrical impulse can propagate
  • Time constant→time that takes for a change in membrane potential to achieve 63% of the new value
59
Q

Why and for what do the F hemoglobin have high oxygen affinity?

A
  • Replacement of Hys by Ser in F Hb→↓positive charge of binding pocket for 2,3 BPG►limit attach of 2,3 BPG, better affinity to O2
  • Facilitates transplacental O2 delivery from the maternal circulation to the fetus
60
Q

What is the segment of the nehpron that is more permeable to water?

A

Proximal tubule reabsorb>60% of the water filtered by the glomeruli regardless patient hydration status

  • Descending loop oh Henle→20% filtered water
  • Late distal tubules and collecting ducts (variable according ADH level)→up to 20% filtered water
61
Q

How is the diffusing capacity for carbon monoxide (DLCO) in emphysema and why?

A

Decreased due to destruction of alveoli and adjoining capillary beds

62
Q

In which type of obstructive pulmonar disease may you have a increased diffusing lung capacity for carbon monoxide? How are the other important parameters?

A
  • Asthma→↑pulmonary capillary blood volumes►↑DLCO

- ↓FEV1/FVC, ↑TLC

63
Q

How can you differentiate the types of restrictive pulmonar disease?

A
  • Extrinsic (Obesity, neuromuscular disease)→↑DLCO

- Intrinsic (interstitial lung diseases)→↓DLCO

64
Q

Which stimulus down regulate gastric acid secretion after meal?

A
  • Intestinal influences→ileum and colon→peptide YY→enterochromaffin like-cells (ECL) histamine-containing►inhibit histamine release (normally + inderectly acid secretion)
  • ECL are + by Gastrin
65
Q

What proteins mediate the decrease concentration of calcium inside de myocyte after excitation and contraction (myocyte relaxation)?

A
  • Na+/Ca2+ exchange pump (NCX)→out 1 Ca2+ by in 3 Na+

- Ca2+-ATPase pump (SERCA)→hydrolysis ATP to put in Ca2+ in SER

66
Q

What protein is required to activate RAS proteins?, What is the pathway and its consequence?

A

GTP→active RAS→(+)RAF→(+)MAP kinase kinase→(+) MAP kinase→(+) transcription factor and gene activation►cell proliferation, etc

67
Q

Which substance is greater in pulmonary veins than pulmonary artery in a patient with heart failure? why?

A

Small pulmonary vessels→endothelial-bound angiotensin-converting enzyme►↑Angiotensin II in pulmonary vein compared to pulmonary artery

68
Q

Functions and source of prostacyclin

A
  • Prostacyclin synthase at capillary endothelium→prostaglandin H2►prostacyclin (prostaglandin I2)
  • Inhibit platelet aggregation, adhesion to vascular endothelium, vasodilation, ↑vascular permeability, ↑leukocyte chemotaxis
69
Q

On which situation may be low or decreased prostacyclin and its consequence?

A
  • Damaged endothelial cells→↓prostacyclin→↑risk thrombi and hemostasis
  • Loss normal dynamic balance with TXA2 (platelet aggregation and vasoconstriction)
70
Q

Major receptors involved in stimulating the vomiting reflex, where is it coordinated?

A
  • M1, D2, H1, 5HT3, Neurokinin 1 (NK1)
  • Area postrema→sense neurotransmitters, drugs or toxins
  • Nucleus tractus solitarius (medulla)→recieve from area postrema, GI tract via X CN, vestibular system, CNS (meninges, hypothalamus); project to other medullary nuclei
71
Q

What process allow the elastin to get a rubber like property?

A

Lysyl oxidase (requires Cu)→oxidatively deaminates lysine residues of tropoelastin at extracellular space→desmosine cross-link between neighboring polypeptides

72
Q

Compensatory mechanism to maintain GFR and RPF if mean arterial pressure rises.

A
  • Afferent arteriole constricts→regulates blood flow to glomerular capillaries→maintain steady flow►Myogenic mechanism of autoregulation (vasoconstriction that occurs when perfusion pressure increases)
  • Metabolic mechanism - vasodilation in response to ↑metabolic waste products
  • Efferent arteriole dilates→dissipates pressure► ↑outfllow from glomerulus
  • EA constricts when MAP is low→↓outflow→sustain filtration pressure
73
Q

Increasing which variable is more effective to improve alveolar ventilation?

A
  • ↑Tidal Volume (VT)→more effective

- ↑Respiration rate→less effective

74
Q

Why does anion gap occur? For example in diabetes ketoacidosis (DKA).

A

Unmeasured anionic ketoacids (ex, beta-hydroxybutyrate, acetoacetate) bind and lower HCO3

75
Q

Coagulation factor with the shortest half-life

A

Factor VII

76
Q

Unique organ that dilate (or decrease vascular resistance) their arteries when tissue oxygen content is elevated

A

Lungs

  • ↓Vascular resistance in well-aerated alveoli
  • Hypoxic vasoconstriction→blood flow is diverted away from underventilated regions toward better ventilated

*Reverse in peripheral circulation→hypoxic tissue→vasodilation►ensure ↑blood flow

77
Q

What hormone of the hypothalamic-pituitary axis is elevated in menopause women?

A

FSH→may be used if clinical Dx is unclear

  • Resistant ovarian follicle
  • Lack negative feedback inhibition from inhibin
78
Q

Why verapamil doesn’t affect the skeletal muscle contraction?

A

Mechanical coupling between L-type Ca+2 channel and RyR from sarcoplasmic reticumul→release of Ca+2 without extracellular entrance of Ca+2 that is blocked by verapamil

*Contraction of cardiac and smooth muscle is dependent of extracellular calcium→block L-type Ca+2 channel→blocks contraction

79
Q

How can TNF-alpha, catecholamines, glucagon glucocorticoids induce to insulin resistance?

A

Activation of serine or threonine kinases→Phosphorylation serine or threonine residues of B-subunits of insulin receptor and insulin receptor substrate-1

80
Q

What is the Böhr-Haldane effect?

A
  • Haldane→binding of O2 to Hb drives the release of H+►plus HCO3 IN RBC changed by Cl [carbonic anhidrase]→CO2 + H2O (Lungs)
  • Böhr→↑CO2 in RBC [carbonic anhidrase]►H+ (bind Hb, ↓affinity by O2), HCO3 (OUT changed by Cl)→unloading O2 from Hb (Peripheral tissues)
81
Q

Effect of increase estrogen activity (pregnancy, post-menopausal hormone replacement tx, ACO use) on free and total thyroid hormones.

A
  • ↑Thyroxine binding globulin (TBG)→binds more free T4, T3→initial ↓of free T3, T4
  • In response normal hypothalamic-pituitary-thyroid axis→transient ↑T4, T3 until new TBG saturates►↑Total T3, T4→free T3, T4 remains normal→Euthyroid►Normal TSH

USMLE Step 1 Flash Cards (9 decks)

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