USMLE Physiology Question Base

A 42-year-old woman complains of a burning pain in the upper middle region of her abdomen. The pain usually occurs about 2 hours after a meal and frequently awakens her at night. Antacids can usually relieve the pain within a few minutes. An endoscopic ultrasound reveals a typical duodenal ulcer identified as a discrete crater in the proximal portion of the duodenal bulb. Because the woman does not have a history of chronic use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs), the bacterium Helicobacter pylori is assumed to be the major factor in the etiology of the ulcer. Which of the following is likely to be normal in this woman?

A series of photographs taken of a middle-aged man over a period of 2 decades demonstrates gradual coarsening of facial features and progressive protrusion of the brows. Upon questioning, the patient reports having to wear larger shoes than he did as a young man. Which of the following pair of hormones normally regulates the hormone responsible for these changes?

Given the data below, what is the net filtration pressure at the glomerulus?

Glomerular hydrostatic pressure = 44 mm Hg
Bowman’s capsule hydrostatic pressure = 9 mm Hg
Osmotic pressure of plasma = 28 mm Hg
Osmotic pressure of tubular fluid = 0

A 50-year-old woman undergoes surgery to remove a large abdominal tumor. Histologic findings show that the mass contains a large number of blood vessels. Several metastases were found 2 months after surgery. A decrease in which of the following is the most likely cause for the development of metastases after the removal of the large tumor?

A 48-year-old man presents to the emergency department with chest pain that radiates to his jaw and left shoulder. Angina pectoris is suspected, and he is sent for an angiogram. The test reveals an atherosclerotic coronary artery that is 50% occluded. The maximal blood flow through this artery is reduces by

A 24-year-old man becomes paraplegic after he severs his spinal cord at T1 in an automobile accident. Chronic constipation is a problem, but he wants to be as independent as possible in its treatment. His physician advises him to distend the rectum digitally on a regular schedule to initiate the defecation reflex. Rectal distention causes which of the following in this patient?

A 26-year-old woman is stranded for more than a week when her hiking trip is interrupted by an avalanche. Because she expected to be gone for only a few hours, she did not bring along any food. Which of the following substances can be converted to glucose to supply the needs of the brain during this period?

A 54-year-old man is seen in clinic with complaints of palpitations and light-headedness. Physical examination is remarkable for a heart rate of greater than 200/min and a blood pressure of 75/40 mm Hg. Which of the following adjustments have probably occurred in the cardiac cycle?

A 25-year-old man visits a friend living in a mountain cabin at an altitude of 5000 meters. After 5 days, he has an increase in ventilation rate and a decrease in arterial Pco­₂. Which of the following physiologic changes is also expected?

As part of an experimental study, a volunteer agrees to have 10 g mannitol injected intravenously. After sufficient time for equilibration, blood is drawn, and the concentration of mannitol in the plasma is found to be 65 mg/100 mL. urinalysis reveals that 10% of the mannitol had been excreted into the urine during this time period. What is the approximate extracellular fluid volume of this volunteer?

A neurophysiologist is studying the functional properties of various receptor subtypes, using whole-cell voltage clamp recordings made from coronal brain slices. At a holding potential of – 70 mV, bath application of receptor agonists for four different receptor types consistently elicited either excitatory postsynaptic currents or inhibitory postsynaptic currents. During the study of one receptor, however, agonist application failed to elicit a postsynaptic response at – 70 mV but did elicit a reliable response at a holding potential of 0 mV. This receptor is most likely which of the following?

In clinical trials, an experimental drug is found to cause impotence in a large percentage of male patients. Inhibition of which of the following could be responsible for this side effect?

A healthy 22-year-old female medical student has an exercise stress test at a local health club. Which of the following is most likely to decrease in her skeletal muscles during exercise?

A young man goes to the gym on his way home from work. He runs on the treadmill for 30 minutes, lifts weights for 20 minutes, and does push-ups and sit-ups for 10 minutes. Which of the following is quantitatively the most important method for transporting the CO₂ in the blood that is produced by his muscles?

A 43-year-old man with a recurrent history of ulcer disease associated with diarrhea and a strong family history of duodenal ulcer disease is suspected of having Zollinger-Ellison syndrome (gastrinoma). While fasting, secretion (1 U/kg) is given as a rapid intravenous injection to test for gastrinoma. Which of the following results would support the existence of gastrinoma following secretin administration?

Medical students are studying the clearance of inulin b the kidneys on a computer-simulated patient. The professor programs the computer so that the patient’s ratio of urinary concentration to plasma concentration of inulin ([U/P] inulin) decreases. Which of the following is true if the glomerular filtration rate remains constant?

Blood is drawn from a 14-year-old boy with bacterial meningitis for a complete blood count. The leukocyte count is elevated. Which of the following is released by the predominant type of white blood cell present?

A 21-year-old man is competing in a weight-lifting competition/. He lifts 325 lb over his head and holds it there for 5 seconds. Suddenly, his arms give away and he drops the weight to the floor. Which of the following receptors is responsible for this sudden muscle relaxation?

A 16-year-old type I diabetic is noncompliant with his required insulin therapy and develops hyperglycemia after eating several pieces of hard candy. The release of which of the following intestinal hormones would most likely be stimulated

A 69-year-old alcoholic has had severe, progressively increasing epigastric pain for the past 24 hours. He has been nauseous, and he vomited three times. Laboratory studies show hypocalcemia and metabolic hypochloremic alkalosis. The primary metabolic effect of the principal hormone secreted by the alpha cells of this organ is

A researcher is studying the substance para-amino-hippuric acid (PAH) and its interaction with the kidneys. She injects a volunteer with the substance. She finds that which of the following can be determined by calculating the clearance of PAH?

A 57-year-old with a 30-year history of alcoholism and liver disease visits her physician complaining of abdominal swelling and shortness of breath. The physician determines that she has severe ascites. Which of the following factors contributes to the accumulation of fluid in the abdominal cavity?

A 33-year-old man complains that his chest hurts when he eats, especially when he eats meat. An x-ray film shows a dilated esophagus, and achalasia is suspected. Esophageal manometry is used to confirm the diagnosis. Swallowing-induced relaxation is reduced at which anatomic location in this man?

A substance that is filtered, but not secreted or reabsorbed (substance X), is infused into a volunteer until a steady-state plasma level of 0.1 mg/mL is achieved. The subject then empties his bladder and waits 1 hour, at which time he urinates again. The volume of urine in the second specimen is 60 mL, and the concentration of substance X is 10 mg/mL. What is the glomerular filtration rate (GFR) in this individual?

A 40-year-old man with sleep apnea participates in a sleep study. During his evaluation, normal saw tooth waves are observed on his EEG tracing. This pattern is associated with which period of sleep?

A 48-year-old white female secretary presents with progressive difficulty typing over the past month. She also notes that her hands begin to feel numb and weak after typing for long periods of time. On testing, which of the following deficits would be predicted?

A 70-year-old woman undergoes a gastrectomy for Zollinger-Ellison syndrome. Her physician informs her that she will need to take intramuscular vitamin B₁₂ shots for the rest of her life. Absence of which of the following cell types are responsible for this vitamin replacement requirement?

A 32-year-old man visits the physician for a periodic health maintenance examination. He has no complains at this time. He is 170 cm (5 ft 7 in) tall and weighs 75 kg (165 lb). Physical examination is unremarkable. In this patient, the volumes of total body water, intracellular fluid, and extracellular fluid are, respectively,

A 35-year-old, sexually active woman visits her gynecologist complaining of mild, right-sided, lower abdominal pain but no other symptoms. There are no peritoneal signs. Her surgical history is significant for an appendectomy at age 10. Her last period occurred 14 days ago. Which of the following endometrial changes corresponds to this stage of the patient’s menstrual cycle?

A 71-year-old woman undergoes an elective sigmoid resection for recurrent diverticulitis. On the second postoperative day, it is noted that her urinary output is averaging only 35 to 45 mL/h. she is receiving 5% dextrose in half normal saline at a rate of 100 mL/h. the intravenous rate of infusion is increased to 125 mL/h. Two days later, her urinary output becomes 15 to 25 mL/h. A sample of urine shows a urinary sodium concentration of 85 mEq/L. laboratory studies show the systemic arterial values as follows:

Which of the following is the most likely diagnosis?

A 47-year-old rent immigrant from Africa has significant edema of the left lower extremity. A polymerase chain reaction assay for DNA of Wuchereria bancrofti is positive. Which sequence of the numbered statements below correctly describes the pathway of the flow from the affected system on the affected side of the body?

1. Junction of left internal jugular and left subclavian
2. Lymph capillaries
3. Thin lymph vessels
4. Thoracic duct

The following data were collected from a normal patient before and after an intervention. Assume that plasma osmolarity and glomerular filtration rate remain constant

The intervention that would best account for the observed changes is

An unlabeled container of blood product is left in a laboratory. The technician must determine whether the sample is serum or plasma. An elevated level of which of the following substances would identify the specimen as plasma?

A Swan-Ganz catheter inserted into a patient with acute respiratory distress syndrome (ARDS) records a pulmonary artery wedge pressure of 6 mm Hg. The same pressure would be expected in which of the following structures?

A hysterical patient is hyperventilating and doubles his alveolar ventilation. If his initial alveolar PA_CO2 was 40 mm Hg, and his CO₂ production remains unchanged, what will his alveolar P_CO2 be on hyperventilation?

A 42-year-old obese woman experiences episodic abdominal pain. She notes that the pain increases after the ingestion of a fatty meal. The action of which of the following hormones is responsible for the postprandial intensification of her symptoms?

A 61-year-old woman develops purple striae on her abdomen and a rounded facial appearance. She has smoked two packs of cigarettes a day for the past 40 years. Chest x-ray shows a 4-cm, centrally located lung mass. This mass is most likely producing a hormone that promotes the production of cortisol by stimulating which of the following reaction?

A 69-year-old man presents with unilateral hearing loss. A lesion in which of the following structures could be responsible for this loss?

A young boy presents with failure to thrive. Biochemical analysis of a duodenal aspirate after a meal reveals a deficiency of enteropeptidase (enterokinase). The levels of which the following digestive enzymes would be affected?

A 45-year-old man has a blood pressure reading of 160/100 mm Hg on three separate visits. He refuses to take antihypertensive medication but is willing to modify his lifestyle in an effort to lower his blood pressure. He quits smoking, joins a health club, and greatly reduces salt from his diet. Which of the following areas of the adrenal gland would be expected to increase in activity because of his diet?

A medical student is studying in the fluid exchange in skeletal muscle capillaries in a laboratory animal. He determines that fluid is being forced out of a capillary with a net filtration pressure of 8 mm Hg, and he obtains the following laboratory values:

Which of the following is the interstitial osmotic pressure?

A 37-year-old woman has been trying to get pregnant for the past 16 months. Just as she is about to schedule an appointment with a fertility specialist, she get a premonition that she is pregnant, despite a negative home pregnancy test 7 days earlier. By the time of implementation in the uterine endometrium, the typical fertilized ovum has divided onto how many cells?

A 24-year-old woman suffers from epistaxis, gingival bleeding, and menorrhagia. Her mother and grandmother have similar symptoms, and her brother has incisional bleeding after surgery and dental extractions. They all have similar laboratory findings, including a prolonged bleeding time, reduced levels of factor VIII antigen, normal platelet aggregation, and reduced ristocerin cofactor activity. This family has a disorder characterized by a deficient or defective protein. In normal patients, which of the following binds to the affected protein at the platelet membrane?

A 25-year-old woman involved in an automobile accident is admitted as an emergency patient. A major artery severed in her leg caused an estimated 600 mL of blood to be lost. Her blood pressure is 90/60 mm Hg. Which of the following would be expected to increase in response to hemorrhage?