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Free STEP1 Exam Braindumps (page: 46)

Page 45 of 213
PDF with 845 Questions

Apatient is admitted to the hospital following a knife wound to the abdomen which results in extensive bleeding into the abdomen. The arterial pressure at admission is 65/30 mm Hg with a rapid, weak pulse. Compared to normal, the nerve impulses in the carotid sinus nerves and in the sympathetic nerves are changed in what way?

  1. both show decreased nerve impulse rates
  2. both show increased nerve impulse rates
  3. carotid sinus nerve impulses are decreased, sympathetic are increased
  4. carotid sinus nerve impulses are increased, sympathetic are decreased
  5. the patient is unconscious so there are no changes in nerve impulse rates

Answer(s): C

Explanation:

The carotid sinus baroreceptors signal the magnitude of arterial pressure to the brainstem which then causes reflex inhibition of sympathetic nerves to the body. Thus, a decrease in arterial pressure will cause a reduced carotid sinus nerve impulse rate, which reflexly increases sympathetic nerve impulse rates.
Hence, choices A, B, and D are directionally incorrect. Choice E is incorrect because the arterial baroreflexes function at the level of the brainstem, which does not require the conscious mind for its action.



A 66-year-old woman is undergoing surgery to repair an abdominal aortic aneurism. During the procedure the abdominal aorta is momentarily clamped below the renal arteries. below figure shows the left ventricular pressure/ volume relationship immediately before (curve 1) and during (curve 2) the aortic occlusion. The change in curve 2 represents an increase in which of the following?

  1. afterload
  2. cardiac output
  3. ejection fraction
  4. preload
  5. stroke volume

Answer(s): A

Explanation:

Clamping of the abdominal aorta suddenly increases peripheral vascular resistance to blood flow. Hence aortic pressure suddenly rises to a high level. This represents an increased afterload, that is, an increased ventricular pressure is required to eject blood into the aort
A. below figure shows that momentary clamping of the aorta does not alter the preload, that is, the filling of the ventricle during diastole (choice D). below figure shows that the inverse relationship between afterload and stroke volume causes a reduced stroke volume (choice E) immediately after aortic clamping. Since end- diastolic volume (preload) is unchanged, while stroke volume is decreased, this represents a decreased ejection fraction (choice C). Cardiac output is calculated as stroke volume X heart rate. Since heart rate is not given, the cardiac output cannot be determined (choice B). However, it is likely, by Ohm's law that a momentary rise in peripheral vascular resistance will decrease cardiac output.



In below figure, which point depicts the excreted glucose in a 31-year-old woman with untreated nephrogenic diabetes insipidus?

  1. A
  2. B
  3. C
  4. D
  5. E

Answer(s): E

Explanation:

Nephrogenic diabetes insipidus is a condition in which the kidney is insensitive to the normal action of ADH, which is to cause a concentrated urine by promoting water reabsorption in the collecting duct. In such a person, plasma glucose will be normal--around 80 mg/ 100 mL and excreted glucose will be zero, since the tubular maximum for glucose has not been exceeded and all the filtered glucose is normally reabsorbed.
Choices A, B, and C depict the filtered, reabsorbed, and excreted glucose in a hyperglycemic state which might occur during diabetes mellitus. Choice D depicts the filtered and reabsorbed glucose in a fasting, normoglycemic state.



Exhibit: *missing*
In below figure, which point depicts the renal filtered glucose in an 11-year-old male with untreated Type I diabetes mellitus?

  1. A
  2. B
  3. C
  4. D
  5. E

Answer(s): A

Explanation:

Type I diabetes mellitus is a condition in which the pancreas secretes inadequate quantities of insulin, causing a fasting hyperglycemia. Choice Adepicts the filtered glucose in such a hyperglycemic state.
Choices B and C depict the reabsorbed and excreted glucose which would also occur in a hyperglycemic state. Choice D depicts the filtered and reabsorbed glucose in a fasting, normoglycemic state. Choice E depicts the zero excreted glucose that would occur in a fasting nondiabetic individual since the tubular maximum for glucose has not been exceeded.






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