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Preclinical medical question bank

Practise every preclinical discipline with explained SBAs.

Recall Engine's preclinical question bank has 13,500+ single best answer questions across 600+ topics in 12 disciplines. The largest are Anatomy and embryology, Physiology, and Pathology. Every question explains each option.

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Preclinical disciplines

Preclinical has 12 disciplines and 600+ topics. Each one below shows its questions and opens its own page with every topic.

Preclinical sample questions

These 5 are published preclinical questions shown exactly as students see them. Open an answer to see why it is right and why every other option is wrong.

Question 1 · Physiology, Preclinical

Which neuron provides the pathway that allows relaxation of the antagonist muscle during stretch of the agonist?

  1. A. Ia inhibitory interneuron
  2. B. Excitatory interneuron crossing the cord
  3. C. Ib inhibitory interneuron
  4. D. γ motor neuron
  5. E. Renshaw cell
Show the answer and explanation

Answer: A. Ia inhibitory interneuron

The Ia inhibitory interneuron provides the pathway for the reciprocal stretch reflex. Contraction of a muscle is accompanied by relaxation of its antagonist through this neuron.

Why the other options are wrong

  • B. Excitatory interneuron crossing the cord: In the crossed extensor reflex an excitatory interneuron crosses to the opposite side to excite the extensors of the opposite limb.
  • C. Ib inhibitory interneuron: The Ib inhibitory interneuron is part of the inverse myotatic reflex, giving relaxation in response to severe stretch or contraction.
  • D. γ motor neuron: γ motor neurons supply the intrafusal fibres.
  • E. Renshaw cell: Renshaw cells inhibit the adjacent α neurons and the active α neuron.

Key point: The Ia inhibitory interneuron mediates reciprocal inhibition, relaxing the antagonist while the stretched agonist contracts.

References

Question 2 · Pathology, Preclinical

A 12-year-old boy whose parents are first cousins develops a red, scaly rash on his face, neck, and the backs of his hands after a feverish illness, together with an unsteady gait and low mood. He eats a varied diet including meat, eggs, and dairy. Plasma amino acids are normal, but urine contains large amounts of tryptophan and other neutral amino acids, while urinary cystine, lysine, arginine, and ornithine are normal. Which defect best explains his findings?

  1. A. Loss of the cystine and dibasic amino acid transporter in kidney
  2. B. Dietary niacin deficiency from a maize-based diet with little protein
  3. C. Deficiency of hepatic phenylalanine hydroxylase
  4. D. Loss of the intestinal glucose and galactose transporter SGLT1
  5. E. Loss of the neutral amino acid transporter in gut and kidney
Show the answer and explanation

Answer: E. Loss of the neutral amino acid transporter in gut and kidney

Hartnup disease is an autosomal recessive defect of the B0AT1 neutral amino acid transporter (SLC6A19) in intestinal and renal tubular cells. Tryptophan is poorly absorbed and lost in urine, giving neutral aminoaciduria with normal plasma levels, so less tryptophan is available to make niacin. Episodes triggered by fever, illness, stress, or poor diet bring a pellagra-like photosensitive rash, cerebellar ataxia, and psychiatric symptoms. Niacin supplements bring a rapid response.

Why the other options are wrong

  • A. Loss of the cystine and dibasic amino acid transporter in kidney: This transporter defect raises urinary cystine, lysine, arginine, and ornithine and forms stones; all four are normal in his urine.
  • B. Dietary niacin deficiency from a maize-based diet with little protein: Dietary pellagra causes a similar rash but no aminoaciduria, and his diet is varied and protein-rich.
  • C. Deficiency of hepatic phenylalanine hydroxylase: This enzyme defect raises plasma phenylalanine, whereas his plasma amino acids are normal and the urine shows a transport loss.
  • D. Loss of the intestinal glucose and galactose transporter SGLT1: This transporter carries sugars, not amino acids; its defect causes neonatal watery diarrhoea, not a rash, ataxia, or aminoaciduria.

Key point: Hartnup disease is a specific malabsorption: a defective neutral amino acid transporter in gut and kidney loses tryptophan, so niacin falls and pellagra-like rash, ataxia, and mood change appear with neutral aminoaciduria.

References

Question 3 · Anatomy and embryology, Preclinical

A second-layer plantar injury affects small muscles beginning on FDL tendons and continuing to toe extensor expansions. Which muscle group has this relationship?

  1. A. Quadratus plantae
  2. B. Flexor digitorum brevis
  3. C. Dorsal interossei
  4. D. Plantar interossei
  5. E. Lumbricals
Show the answer and explanation

Answer: E. Lumbricals

Lumbricals begin on the FDL tendons rather than the metatarsal shafts.

Why the other options are wrong

  • A. Quadratus plantae: It lies in layer 2 and attaches to the FDL tendon. The decisive case relationship is: Lumbricals begin on the FDL tendons rather than the metatarsal shafts.
  • B. Flexor digitorum brevis: It lies centrally in layer 1 and reaches middle phalanges of toes 2-5. The decisive case relationship is: Lumbricals begin on the FDL tendons rather than the metatarsal shafts.
  • C. Dorsal interossei: Four muscles abduct toes relative to the second-toe axis. The decisive case relationship is: Lumbricals begin on the FDL tendons rather than the metatarsal shafts.
  • D. Plantar interossei: Three muscles adduct toes toward the second-toe axis. The decisive case relationship is: Lumbricals begin on the FDL tendons rather than the metatarsal shafts.

Key point: Foot lumbricals arise from FDL tendons.

References

Question 4 · Biostatistics and epidemiology, Preclinical

Which statement about active surveillance is correct?

  1. A. It relies on providers reporting disease occurrence to a higher level
  2. B. It generally relies on data from electronic health information systems
  3. C. It is widely used because it is relatively inexpensive
  4. D. It requires substantially more time and resources, so it is less commonly used
  5. E. Its data come from selected sites with good laboratory facilities
Show the answer and explanation

Answer: D. It requires substantially more time and resources, so it is less commonly used

Active surveillance recruits project staff specifically for the task and uses periodic field visits for case finding. Reporting is generally more accurate, but it requires substantially more time and resources and is therefore less commonly used.

Why the other options are wrong

  • A. It relies on providers reporting disease occurrence to a higher level: Passive surveillance relies on health-care providers, laboratories, hospitals, health facilities, and private practitioners reporting the occurrence of a disease to a higher administrative level.
  • B. It generally relies on data from electronic health information systems: Syndromic surveillance generally relies on data from electronic health information systems.
  • C. It is widely used because it is relatively inexpensive: Passive surveillance is widely used because it is relatively inexpensive and relatively easy to develop initially.
  • E. Its data come from selected sites with good laboratory facilities: Selected reporting units with good laboratory facilities and experienced staff are used in sentinel surveillance.

Key point: Active surveillance is more accurate but needs substantially more time and resources, so it is less commonly used.

Question 5 · Microbiology, Preclinical

A 20-year-old student has had fever, conjunctivitis, and a maculopapular rash for 3 days during a measles outbreak on campus. She does not know her vaccination history. A serum taken today is measles IgG positive. The public health team needs a diagnosis of acute infection as fast as possible. Which serological step gives that answer most quickly?

  1. A. IgG repeated on a second serum taken in 2 days
  2. B. Today's positive IgG reported as acute infection
  3. C. IgG titre of today's serum by latex agglutination
  4. D. Measles-specific IgM on today's serum
  5. E. IgG on today's serum and on a serum 2 to 3 weeks later
Show the answer and explanation

Answer: D. Measles-specific IgM on today's serum

IgM is made first in a primary response and can be detected in a single serum, so it gives a rapid diagnosis of acute infection. IgG alone is ambiguous here because it may come from vaccination or past infection. A rising IgG also works, but only with acute and convalescent sera at least 10 days apart (CDC protocols use 2 to 4 weeks and a fourfold rise), which is too slow for outbreak control.

Why the other options are wrong

  • A. IgG repeated on a second serum taken in 2 days: Two days is far too short for a meaningful IgG rise; paired sera must be at least 10 days apart, and usually 2 to 4 weeks.
  • B. Today's positive IgG reported as acute infection: A single positive IgG may reflect past vaccination or infection, which her unknown history does not exclude, so it cannot diagnose acute measles.
  • C. IgG titre of today's serum by latex agglutination: A single titre has no baseline for comparison, so even a high value cannot separate acute from past infection.
  • E. IgG on today's serum and on a serum 2 to 3 weeks later: Paired IgG can show a fourfold rise, but it needs a convalescent sample weeks later, so it cannot give the fast answer the outbreak team needs.

Key point: For a rapid diagnosis of acute viral infection, test virus-specific IgM in a single serum; IgG needs paired sera weeks apart showing a significant (usually fourfold) rise.

References

More of the question bank

Each stage and each discipline has its own page with its topics and sample questions. The question bank page shows the whole library and how practice works.

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