According to NBCE, Part I is a computer-based basic-science exam of 255 questions across six domains—General Anatomy, Spinal Anatomy, Physiology, Chemistry, Pathology, and Microbiology—given in two sessions with 3 hours 26 minutes of testing time; NBCE also lists a minimum passing score of 375, a $710 fee, and domain-level sample tests. The four topic labels on this page are broader groupings, not the six-domain test plan, so do not use them to infer item counts or weightings. This knowledge preview is an original review aid, not an official NBCE product or a full simulation; verify current eligibility, test plan, fees, scheduling, and test-site rules with NBCE before applying. Content is subject to review against current NBCE publications. Use the 20 questions as a diagnostic and mechanism drill, not a score prediction. Study the six-domain test plan, practice lesion-to-deficit and data interpretation, and complete the integrated task before checking the rubric.
What the exam actually asks you to do
Part I rewards mechanism-based recall, lesion localization, and interpretation of simple data—not isolated vocabulary.
NBCE identifies six basic-science domains and describes Part I as a computer-based exam of 255 questions in two sessions, with 3 hours 26 minutes of testing time. The four topic labels on this page are broader groupings, but the official structure is the six-domain blueprint. Treat this 20-item preview as a mechanism check, not a score prediction or a substitute for the official sample tests.
Tested skills recur: map anatomy to function, predict deficits from a lesion, follow a physiological feedback loop, calculate a simple biochemical value, recognize a pathologic pattern, and identify an organism from a described feature. Many items are two-step: you must first recall a fact and then apply it to a short scenario. For example, knowing that the radial nerve supplies wrist extensors is not enough; you must connect a midshaft humeral fracture to wrist drop.
Use a three-pass review. First, build a one-page mechanism sheet per domain. Second, answer mixed questions and write the reason each wrong option fails. Third, revisit only weak mechanisms after 48 hours and again after a week. Administrative details from the supplied pages—including the stated 375 passing score and $710 fee—should be reverified with NBCE because they are not study content.
Prioritize by blueprint, then by mechanism
Anatomy is the largest block, but broad coverage plus mechanism drill is safer than chasing one domain.
The supplied test plan lists General Anatomy at 20%, Spinal Anatomy at 22%, Physiology at 18%, Chemistry at 13%, Pathology at 16%, and Microbiology at 11%. Anatomy and spinal anatomy together are the largest block, so they deserve early and repeated attention. Do not skip chemistry or microbiology; a balanced strategy protects you from a single weak domain.
Use the subtopics as a checklist, not as proof of a technical rule. Build a matrix with rows for domains and columns for recall, application, and data interpretation. Mark gaps. If time is short, protect mechanisms that support multiple domains: nerve injury localization, spinal tract anatomy, Starling forces, and acid-base buffering. These recur in anatomy, physiology, pathology, and clinical reasoning.
A useful weekly limit is two new mechanisms plus one mixed set per study block. More content without retrieval practice produces weak retention. When a question goes wrong, label the error as recall, localization, calculation, or misread—then repair that specific link.
Anatomy: learn nerves, muscles, and embryology as chains
Peripheral nerve items reward a three-link chain: injury site, nerve at risk, and lost muscles or skin.
Peripheral nerve questions reward a three-link chain: fracture or laceration site → nerve at risk → muscles and skin lost. A midshaft humerus fracture threatens the radial nerve in the spiral groove. The radial nerve supplies the wrist extensors and the dorsal first web space. The predicted pattern is wrist drop, weakened wrist extension, and reduced sensation over the dorsal first web; triceps may be spared depending on level. A wrong option often names a different nerve with a plausible but inconsistent deficit.
Shoulder abduction is another chain. Supraspinatus initiates the first part of abduction; deltoid is the major abductor after that. Rotator cuff muscles stabilize the humeral head. A question may describe pain with overhead activity and ask which function is most impaired, or which muscle stabilizes. Answer by linking muscle, nerve, and joint motion, not by memorizing a list.
Embryology is best learned by timing. Neural tube closure occurs early, so failed closure can produce cranial or spinal defects depending on the site. Pharyngeal arch derivatives are easier when you attach each arch to a nerve, muscle, and cartilage group. Do not use a topic title as a rule; write the actual derivative. For congenital malformations, ask: what process was happening at that time?
Spinal anatomy: restraint, root, and tract
Separate disc level from root level, and separate dorsal-column from spinothalamic findings.
A posterolateral disc herniation is constrained by the posterior longitudinal ligament, which is stronger centrally and thinner laterally. That anatomy explains why a lateral herniation can compress a nerve root. At L4–L5, a posterolateral herniation most often affects the L5 root, producing weakness of ankle dorsiflexion and great-toe extension and sensory change over the dorsum of the foot. At L5–S1, the S1 root is the usual target, with reduced ankle reflex and plantarflexion weakness. Use the disc level and the root level separately; candidates often confuse them.
Dermatomes and myotomes are maps, not absolute boundaries. The umbilicus is T10; the nipple line is T4; the inguinal region is L1. For a described sensory level, ask whether the pattern fits a root, a peripheral nerve, or a spinal cord tract. Spinal cord tracts produce dissociated patterns. A right dorsal column lesion at T6 causes loss of vibration and proprioception in the right leg below the lesion, because the dorsal columns ascend ipsilaterally. A right spinothalamic lesion causes loss of pain and temperature on the left below the lesion, because those fibers cross near their entry level.
Upper versus lower motor neuron signs are a fast localization tool. Upper motor neuron lesions produce spasticity, hyperreflexia, and a Babinski sign; lower motor neuron lesions produce flaccidity, atrophy, fasciculations, and reduced reflexes. A lesion can produce both if it involves the cord and root, so read the whole scenario.
Physiology and chemistry: follow the gradient and do the arithmetic
Draw feedback loops, use simple equations, and always check expected compensation.
Action potentials are driven by ion permeability changes. Depolarization reflects increased sodium conductance; repolarization reflects potassium conductance and sodium inactivation. Synaptic transmission depends on calcium entry and transmitter release. For endocrine items, draw the feedback loop: stimulus → hormone → target effect → negative feedback. For example, potassium directly stimulates aldosterone secretion, which increases renal potassium excretion.
Enzyme kinetics are testable with one equation. For Michaelis-Menten behavior, v = Vmax[S]/(Km+[S]). When [S] equals Km, v = Vmax × Km/(Km+Km) = 0.5 Vmax. A question that gives [S] as twice Km yields 2/3 Vmax; three times Km yields 3/4 Vmax. Do not memorize only the graph; compute the ratio.
Acid-base questions belong to renal and body-fluid physiology. Use a five-step check: pH, PaCO2, HCO3, expected compensation, and cause. In a worked example, pH 7.30, PaCO2 30 mmHg, and HCO3 15 mEq/L indicate acidemia with low bicarbonate, so the primary process is metabolic acidosis. Winter's formula gives expected PaCO2 ≈ 1.5 × 15 + 8 = 30.5 mmHg, with a ±2 range, so the respiratory compensation is appropriate. If PaCO2 were 45 mmHg, the same bicarbonate would indicate a second respiratory acidosis. For chemistry, focus on biochemical energetics and redox: high-energy phosphate compounds such as ATP couple exergonic and endergonic reactions, and the electron transport chain uses redox carriers to drive proton pumping and oxidative phosphorylation. The bicarbonate pair HCO3−/H2CO3 is part of acid-base physiology, where ventilation alters dissolved CO2 and shifts pH.
Pathology and microbiology: pattern plus context
Match morphology to mechanism, fluid to Starling forces, and organisms to a hierarchy of features.
Cell injury questions often ask you to match morphology to mechanism. Coagulative necrosis preserves tissue architecture and follows ischemia in most organs; liquefactive necrosis occurs in brain infarcts and abscesses; caseous necrosis accompanies granulomatous inflammation; fat necrosis follows pancreatic injury. Do not choose a necrosis type just because an organ is named; connect the mechanism.
Starling forces explain fluid patterns. Increased capillary hydrostatic pressure or decreased plasma oncotic pressure favors transudate; increased capillary permeability favors exudate, which is protein-rich. A worked scenario: hypoalbuminemia lowers plasma oncotic pressure, shifting fluid into the interstitium and producing a transudative effusion with low protein. Inflammation instead increases permeability and produces a high-protein exudate. These are conceptual distinctions, not treatment instructions.
Microbiology identification uses a hierarchy: Gram reaction, morphology, arrangement, oxygen requirement, and key biochemical or host features. Gram-positive cocci in clusters that are catalase-positive suggest Staphylococcus aureus; gram-positive cocci in chains suggest Streptococcus. A prion is an infectious protein without nucleic acid, unlike a virus. Learn the distinguishing feature first, then the disease example.
Integrated practice task and self-check rubric
Use one short case to connect anatomy, tracts, fluid physiology, microbiology, and red-flag reasoning.
Try this open-task practice without looking up answers. A 48-year-old office worker develops sudden low back pain and right leg pain after lifting. Examination shows reduced right ankle dorsiflexion and great-toe extension, with reduced sensation over the dorsum of the foot. There is no bowel or bladder dysfunction and no saddle anesthesia. Radiographs are unremarkable. Prompts: (1) Which disc level and root are most likely? (2) Which spinal tract would explain a separate loss of vibration sense? (3) Distinguish upper and lower motor neuron signs. (4) Explain one Starling-force mechanism that could produce edema. (5) Name one organism-identification principle from microbiology. (6) Identify red flags that would require urgent evaluation.
Self-check rubric: 2 points = names L4–L5 disc and L5 root, explains dorsiflexion, great-toe extension, and dorsal foot sensory distribution, and does not confuse reflex level. 1 point = right root but incomplete explanation. Dorsal column answer: ipsilateral vibration and proprioception loss below a lesion. UMNL/LMNL answer: spasticity, hyperreflexia, and Babinski versus flaccidity, atrophy, fasciculations, and reduced reflexes. Edema answer: low albumin lowers oncotic pressure and favors transudate; inflammation raises permeability and favors exudate. Microbiology answer: Gram reaction plus morphology and arrangement narrows identification. Red flags: saddle anesthesia, new bowel or bladder dysfunction, bilateral or progressive weakness, fever, cancer history, or trauma. Score 10–12 strong; 7–9 review weak links; below 7 reread the relevant sections. This is an open reasoning task, not a simulated Part I station.
Common errors and a practical study sequence
Repair links, not just facts, and review errors on a spaced schedule.
Common errors: memorizing a nerve name without its muscles and sensory territory; confusing disc level with root level; mixing dermatome and myotome; treating upper motor neuron signs as weakness only; using transudate and exudate as synonyms; memorizing enzyme graphs without calculating ratios; ignoring expected compensation in acid-base problems; and choosing an organism from Gram stain alone when arrangement or biochemistry is needed.
Six-week sequence, adjustable to your schedule: Week 1—General Anatomy with nerve-lesion chains and embryology timing. Week 2—Spinal Anatomy with tract diagrams, dermatomes, and disc-root scenarios. Week 3—Physiology: action potentials, feedback, and renal acid-base. Week 4—Chemistry: enzyme calculations, bioenergetics, and hormone metabolic effects; revisit physiology acid-base with Week 3. Week 5—Pathology and Microbiology: necrosis, Starling forces, inflammation, and organism identification. Week 6—mixed timed blocks and the integrated task. Each study block: 20 minutes recall, 30 minutes worked mechanisms, 20 minutes mixed questions, and 10 minutes error log. Review errors after 48 hours and after 7 days. Use official sample tests if available; they provide an overall score and do not show which questions were answered correctly or incorrectly, so use them for timed mixed practice and study the underlying mechanisms independently.
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.