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Free STEP1 Exam Braindumps (page: 47)

Page 46 of 213
PDF with 845 Questions

A 57-year-old woman presents with an arterial pressure of 180/115 mm Hg, and blood creatinine levels are elevated. Renal angiography reveals a severe bilateral stenosis of the renal arteries. Which of the following are elevated also?

  1. ADH secretion
  2. GFR
  3. para-aminohippurate (PAH) clearance
  4. renin secretion
  5. urine output

Answer(s): D

Explanation:

The bilateral renal artery stenosis will reduce renal perfusion pressure. Hence the juxtaglomerular apparatus will greatly increase renin secretion which causes the large rise in arterial pressure because of the vasoconstrictor action of angiotensin II. A reduced renal perfusion pressure will decrease PAH clearance (choice C), which estimates renal blood flow and will reduce GFR (choice B). The decreased formation of tubular fluid will result in reduced urine output (choice E) and the large rise in arterial pressure will activate arterial baroreceptors and suppress ADH secretion from the posterior pituitary (choice A).



A patient with untreated diabetes mellitus is admitted to the hospital for treatment. Laboratory findings include a blood pH below 7.2. Which of the following is likely to directly result from this level of acidemia?

  1. arteriolar constriction
  2. decreased catabolism
  3. hyperkalemia
  4. hypoventilation
  5. insulin sensitivity

Answer(s): C

Explanation:

Acidemia is the presence of excess ions in blood, which tends to create a rise in the extracellular potassium concentration. The rule of thumb for an inorganic acid that causes the acidity is that a decrease in pH of 0.1 unit leads to a rise in plasma potassium of 0.6 milliequivalents per liter. The effect of an organic acid is a lot less. The mechanism responsible for the relationship between pH and extracellular potassium concentration is not completely understood. One effect is that the intracellular acidosis inhibits influx by reducing the activity of the Na-K-pump. An exchange of extracellular for intracellular might also contribute. Choices A, B, D, and E are the opposite of what is observed in acidemia.



During a routine preschool examination, a 5-year-old boy is found to have difficulty focusing on distant objects. Which of the following is true during far accommodation of the eyes?

  1. ciliary muscles are relaxed
  2. pupils are constricted
  3. the focal length of the lens is short
  4. the lens is rounded
  5. zonula fibers are relaxed

Answer(s): A

Explanation:

This patient probably suffers from myopia (nearsightedness). Myopia is either due to eyeballs that are too long or a lens that is too strong. To focus a distant object onto the retina (far accommodation), the lens has to decrease its refractive power (i.e., increase its focal length). This is accomplished through relaxation of the ciliary muscles that oppose the pull of the sclera, resulting in a tightening of the zonula fibers and a flattening of the lens. Shortening of the focal length (choice C), rounding of the lens (choice D), and relaxation of the zonular fibers (choice E), all occur during near accommodation. The pupils also constrict during near accommodation (choice B), perhaps to increase depth of field.



Although most cases of hypertension are "essential, " meaning the underlying disorder is unknown, about 10% of cases are "secondary hypertension" due to a specific, usually treatable cause. Which of the following alternatives can lead to secondary hypertension?

  1. adrenal insufficiency
  2. estrogen deficiency
  3. hyperparathyroidism
  4. renal artery stenosis
  5. volume depletion

Answer(s): D

Explanation:

A fixed lesion of the renal artery results in impaired perfusion. When the kidney is poorly perfused, it increases renin secretion, which increases blood pressure and thus improves renal blood flow. Hence the appropriate treatment is surgical correction of the renal artery lesion. Adrenal insufficiency (choice A), estrogen deficiency (choice B), and volume depletion (choice E) are situations that tend to diminish blood pressure. There is no clear relationship between hyperparathyroidism (choice C) and hypertension.






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