A 64-year-old man with coronary artery disease and hypertension comes to the physician for a follow-up examination. His blood pressure ranged from 160/100 mm Hg to 150/94 mm Hg on his previous 3 visits over the past 4 months. Current medications include aspirin, atorvastatin, hydrochlorothiazide, and metoprolol. Three weeks ago, he was also started on amlodipine. His blood pressure today is 158/98 mm Hg. Physical examination shows no other abnormalities. Renal duplex ultrasonography shows 90% occlusion of the right renal artery. Decreased renal blood flow is most likely to cause which of the following?

A 46-year-old woman comes to the physician for a 6-month history of worsening bronchial asthma control. Before this issue began, she only used her salbutamol inhaler once a day. Now, she has to use it multiple times daily and also reports frequent nighttime awakening. Seven months ago, she moved to an apartment that is damp and has mold on some of the walls. The physician injects 0.1 mL of Candida albicans extract on the mid-volar surface of the right arm intradermally. After 48 hours there is a palpable induration of 17 mm. This reaction is most likely a result of release of which of the following substances?

An investigator is studying physiological changes in the autonomic nervous system in response to different stimuli. 40 μg of epinephrine is infused in a healthy volunteer over a period of 5 minutes, and phenoxybenzamine is subsequently administered. Which of the following effects is most likely to be observed in this volunteer?

A 56-year-old woman is admitted to the hospital for progressive bilateral lower extremity weakness and absent deep tendon reflexes. Cerebrospinal fluid analysis shows an elevated protein concentration and a normal cell count. Treatment with plasmapheresis is initiated, after which her symptoms start to improve. Four weeks after her initial presentation, physical examination shows normal muscle strength in the bilateral lower extremities and 2+ deep tendon reflexes. Which of the following changes in neuronal properties is the most likely explanation for the improvement in her neurological examination?

A 75-year-old man with a seizure disorder is brought to the emergency department by a friend because of progressive confusion over the past two weeks. He is unable to provide any history. His vital signs are within normal limits. He appears lethargic and is only oriented to person. Oral mucosa is moist. There is no jugular venous distention. A basic metabolic panel shows a serum sodium concentration of 115 mEq/L but is otherwise normal. Serum osmolality is low and antidiuretic hormone level is elevated. X-ray of the chest shows no abnormalities. Which of the following is the most likely cause of this patient’s hyponatremia?

An investigator is studying the effects of different gastrointestinal regulatory substances. A healthy subject is asked to eat a meal at hour 0, and the pH of the stomach contents and the rate of stomach acid secretions are measured over the next 4 hours. The results of the study are shown. Which of the following mechanism most likely contributes to the change in trajectory of the graph at the point marked by the arrow?

A 32-year-old professional runner is preparing for an upcoming competition in a high-altitude training camp in Ethiopia. He usually trains near sea level. The campsite is at 2,800 m (9,200 ft) above sea level, and his training includes several runs to an altitude of 4,000 m (13,000 ft). After 7 days, his blood is drawn by his supervising physician. Which of the following sets of arterial blood gas findings is most likely?

A 75-year-old man comes to the physician because of a 4-month history of progressive shortness of breath and chest pressure with exertion. Cardiac examination shows a crescendo-decrescendo systolic murmur that is heard best in the second right intercostal space. Radial pulses are decreased and delayed bilaterally. Transesophageal echocardiography shows hypertrophy of the left ventricle and a thick, calcified aortic valve. The area of the left ventricular outflow tract is 30.6 mm2. Using continuous-wave Doppler measurements, the left ventricular outflow tract velocity is 1.0 m/s, and the peak aortic valve velocity is 3.0 m/s. Which of the following values most closely represents the area of the stenotic aortic valve?

An 8-year-old boy is brought to the physician because of a 2-month history of headaches. He is at the 25th percentile for weight and 80th percentile for height. His vital signs are within normal limits. Physical examination shows no abnormalities. CT scan of the head shows a small suprasellar cystic mass compressing the infundibular stalk. Serum concentration of which of the following hormones is most likely to be increased in this patient?

A 75-year-old man is brought to the emergency room 4 hours after the sudden onset of excruciating pain in his right calf. He has smoked 1 pack of cigarettes daily for 40 years. The right foot is cold and pale, and palpation of the right posterior tibial artery shows no pulse. Muscle strength is 1/5 and sensation to touch is significantly decreased in the right lower extremity. His serum creatinine kinase concentration is elevated. Arterial duplex sonography shows absent blood flow distal to the right popliteal artery. Compared with a healthy adult, which of the following sets of intracellular electrolyte concentrations are most likely to be found in this patient's right distal gastrocnemius muscle?