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Physiology — Step 1 practice questions
446 questions in this area, with an explanation for every answer choice.
Three samples below, free and without an account.
How this shows up on Step 1
Physiology questions can be reasoned rather than recalled, which makes them the best return on study time. Most present a perturbation and ask what happens next. If you can draw the relevant curve or loop, you can usually answer without having seen that exact question before.
Sample questions
Sample question 1
A patient has a holosystolic murmur heard best at the apex radiating to the axilla, with a soft S1 and an S3. Which of the following is the most likely lesion?
Explanations
A. Mitral stenosis with an opening snap and diastolic rumble
Mitral stenosis produces a diastolic murmur.
B. Mitral regurgitation, in which retrograde flow into the left atrium throughout systole produces a holosystolic apical murmur radiating to the axilla · correct
Mitral regurgitation produces a HOLOSYSTOLIC murmur because the pressure gradient between ventricle and atrium exists throughout systole, heard best at the APEX with radiation to the AXILLA, often with a soft S1 and an S3 from the volume-loaded ventricle. Contrast the other left-sided lesions: AORTIC STENOSIS gives a crescendo-decrescendo systolic murmur at the right upper sternal border radiating to the carotids with delayed carotid upstroke; MITRAL STENOSIS gives an opening snap with a diastolic rumble; and AORTIC REGURGITATION gives an early decrescendo diastolic murmur with a wide pulse pressure.
C. Aortic stenosis with a crescendo-decrescendo murmur radiating to the carotids
Aortic stenosis radiates to the carotids and is not holosystolic.
D. Tricuspid regurgitation increasing with expiration
Right-sided murmurs increase with INSPIRATION.
E. Aortic regurgitation with a decrescendo diastolic murmur
Aortic regurgitation is diastolic.
Sample question 2
Parents of a 4-month-old ask when their infant will sleep through the night. Which of the following best describes normal infant sleep development?
Explanations
A. Night waking beyond 4 months always indicates a sleep disorder
Brief night waking remains developmentally normal.
B. Newborns have a well-established circadian rhythm from birth
Circadian rhythm develops over the first months of life.
C. Infants should be placed prone to promote longer sleep
Prone positioning substantially increases the risk of sudden infant death.
D. Sleep consolidates gradually over the first year as circadian rhythm matures, with many infants sleeping longer stretches by 4–6 months, and brief night wakings remaining normal thereafter · correct
Newborns lack a mature CIRCADIAN rhythm, sleeping in short bouts distributed across day and night, with melatonin secretion and day-night entrainment developing over the first months. Sleep gradually CONSOLIDATES, and many infants sleep longer nocturnal stretches by 4–6 months, though brief night wakings persist normally well beyond that — infants who "sleep through" typically still wake briefly and self-soothe. Newborns also spend far more time in REM (active) sleep than adults. Safe sleep guidance remains SUPINE positioning on a firm surface, and introducing solids does not improve sleep.
E. Introducing solids at 3 months reliably produces sleeping through the night
Early solids do not improve sleep and carry other risks.
Sample question 3
A 60-year-old woman with multiple myeloma has polyuria and polydipsia with a serum calcium of 13.2 mg/dL. Urine osmolality remains low after water deprivation and does not respond to desmopressin. Which of the following best explains her concentrating defect?
Explanations
A. Destruction of the posterior pituitary by tumor
Posterior pituitary destruction would cause CENTRAL DI, which responds to desmopressin.
B. Osmotic diuresis from hyperglycemia
Osmotic diuresis produces concentrated urine with high osmolality.
C. Excess ADH secretion causing receptor downregulation
ADH is appropriately elevated but ineffective at the kidney.
D. Primary polydipsia washing out the medullary gradient only
Primary polydipsia would show appropriate concentration during water deprivation.
E. Hypercalcemia activates the calcium-sensing receptor in the thick ascending limb and collecting duct, reducing NKCC2 activity and aquaporin-2 responsiveness to ADH · correct
Hypercalcemia causes acquired nephrogenic diabetes insipidus: activation of the basolateral calcium-sensing receptor in the thick ascending limb inhibits NaCl reabsorption (dissipating the medullary gradient) and reduces aquaporin-2 insertion in collecting duct cells, so the kidney cannot concentrate urine despite ADH. Lithium, hypokalemia, and demeclocycline act similarly. Treat the hypercalcemia; thiazides and amiloride help in persistent nephrogenic DI.
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