High-Yield
Anatomy & Physiology
Pre-Clinical Core & USMLE® Step 1 Review
2026 Edition
System-by-system rapid review • Clinical correlations • Buzzwords • High-yield tables
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 1 of 20
,High-Yield Anatomy & Physiology — USMLE Step 1 Review
This guide condenses the most heavily tested anatomy and physiology of the pre-clinical years into a rapid,
system-by-system review. Each chapter pairs core mechanisms with the clinical correlations, buzzwords, and
"first-order" reasoning that Step 1 rewards. Use it as a final-pass consolidation tool alongside question banks.
Pearls (orange) flag the high-yield testable points; buzz boxes (green) list classic vignette cues.
Contents
1. Cell Physiology & Membrane Transport
2. Nervous System & Neurophysiology
3. Cardiovascular System
4. Respiratory System
5. Renal System & Acid–Base
6. Gastrointestinal System
7. Endocrine System
8. Musculoskeletal System
9. Hematology & Immune Physiology
10. Reproductive System
11. Rapid-Review High-Yield Tables
1. Cell Physiology & Membrane Transport
Membrane Transport
• Simple diffusion: lipophilic/small molecules (O₂, CO₂, steroids) down gradient, no protein.
• Facilitated diffusion: carrier-mediated, down gradient, saturable (e.g., GLUT transporters).
• Primary active transport: ATP-driven against gradient — Na⁺/K⁺-ATPase (3 Na⁺ out, 2 K⁺ in),
Ca₂⁺-ATPase, H⁺/K⁺-ATPase (gastric).
• Secondary active transport: uses Na⁺ gradient — symport (SGLT, Na⁺-glucose) and antiport (Na⁺/
Ca₂⁺ exchanger).
Pearl: The Na⁺/K⁺-ATPase is the engine behind the resting membrane potential and nearly all secondary transport.
Cardiac glycosides (digoxin) inhibit it → ↑ intracellular Na⁺ → less Na⁺/Ca₂⁺ exchange → ↑ intracellular Ca₂⁺ →
positive inotropy.
Resting & Action Potentials
• Resting membrane potential (~−70 mV) is set mainly by K⁺ permeability (Nernst/GHK).
• Depolarization: fast voltage-gated Na⁺ influx. Repolarization: K⁺ efflux. Hyperpolarization: K⁺
overshoot.
• Absolute refractory period (Na⁺ channels inactivated) prevents tetany / back-propagation.
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 2 of 20
, Cell Biology Essentials
• RER: secretory/membrane protein synthesis (rich in Nissl bodies in neurons, plasma cells).
• SER: steroid & detox (liver hepatocytes, adrenal cortex, gonads).
• Golgi: post-translational modification; mannose-6-phosphate tags lysosomal enzymes (defect → I-
cell disease).
• Mitochondria: maternally inherited; oxidative phosphorylation.
Vignette cues: "Whorled membranes / foamy macrophages" → lysosomal storage; "abundant RER" → plasma cell /
secretory; "cells with clear cytoplasm, lots of SER" → steroid-producing.
2. Nervous System & Neurophysiology
Neuron & Synapse
• Resting and graded potentials summate at the axon hillock; threshold triggers all-or-none AP.
• Saltatory conduction along myelinated axons (nodes of Ranvier). Demyelination (MS, Guillain-Barré)
slows/blocks conduction.
• Neurotransmitters: ACh, glutamate (excitatory), GABA/glycine (inhibitory), dopamine, NE, serotonin.
Key CNS Anatomy (High-Yield)
Structure Function / Lesion
Frontal lobe (prefrontal) Executive function, personality; lesion → disinhibition
Broca area (inf. frontal) Motor speech; lesion → non-fluent aphasia
Wernicke area (sup. temporal) Comprehension; lesion → fluent aphasia
Amygdala Fear/emotion; bilateral lesion → Klüver-Bucy
Hippocampus Memory formation; lesion → anterograde amnesia
Cerebellum Coordination; lesion → ipsilateral ataxia, intention tremor
Basal ganglia Movement modulation; Parkinson, Huntington
Internal capsule Lacunar stroke → pure motor hemiparesis
Spinal Tracts
• Dorsal column: fine touch, proprioception, vibration; decussates in medulla.
• Spinothalamic: pain/temperature; decussates 1–2 levels above entry.
• Corticospinal: voluntary motor; decussates at medullary pyramids.
Pearl: Brown-Séquard (hemisection): ipsilateral loss of motor + dorsal column below lesion; contralateral pain/temp
loss starting 1–2 levels below.
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 3 of 20
Anatomy & Physiology
Pre-Clinical Core & USMLE® Step 1 Review
2026 Edition
System-by-system rapid review • Clinical correlations • Buzzwords • High-yield tables
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 1 of 20
,High-Yield Anatomy & Physiology — USMLE Step 1 Review
This guide condenses the most heavily tested anatomy and physiology of the pre-clinical years into a rapid,
system-by-system review. Each chapter pairs core mechanisms with the clinical correlations, buzzwords, and
"first-order" reasoning that Step 1 rewards. Use it as a final-pass consolidation tool alongside question banks.
Pearls (orange) flag the high-yield testable points; buzz boxes (green) list classic vignette cues.
Contents
1. Cell Physiology & Membrane Transport
2. Nervous System & Neurophysiology
3. Cardiovascular System
4. Respiratory System
5. Renal System & Acid–Base
6. Gastrointestinal System
7. Endocrine System
8. Musculoskeletal System
9. Hematology & Immune Physiology
10. Reproductive System
11. Rapid-Review High-Yield Tables
1. Cell Physiology & Membrane Transport
Membrane Transport
• Simple diffusion: lipophilic/small molecules (O₂, CO₂, steroids) down gradient, no protein.
• Facilitated diffusion: carrier-mediated, down gradient, saturable (e.g., GLUT transporters).
• Primary active transport: ATP-driven against gradient — Na⁺/K⁺-ATPase (3 Na⁺ out, 2 K⁺ in),
Ca₂⁺-ATPase, H⁺/K⁺-ATPase (gastric).
• Secondary active transport: uses Na⁺ gradient — symport (SGLT, Na⁺-glucose) and antiport (Na⁺/
Ca₂⁺ exchanger).
Pearl: The Na⁺/K⁺-ATPase is the engine behind the resting membrane potential and nearly all secondary transport.
Cardiac glycosides (digoxin) inhibit it → ↑ intracellular Na⁺ → less Na⁺/Ca₂⁺ exchange → ↑ intracellular Ca₂⁺ →
positive inotropy.
Resting & Action Potentials
• Resting membrane potential (~−70 mV) is set mainly by K⁺ permeability (Nernst/GHK).
• Depolarization: fast voltage-gated Na⁺ influx. Repolarization: K⁺ efflux. Hyperpolarization: K⁺
overshoot.
• Absolute refractory period (Na⁺ channels inactivated) prevents tetany / back-propagation.
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 2 of 20
, Cell Biology Essentials
• RER: secretory/membrane protein synthesis (rich in Nissl bodies in neurons, plasma cells).
• SER: steroid & detox (liver hepatocytes, adrenal cortex, gonads).
• Golgi: post-translational modification; mannose-6-phosphate tags lysosomal enzymes (defect → I-
cell disease).
• Mitochondria: maternally inherited; oxidative phosphorylation.
Vignette cues: "Whorled membranes / foamy macrophages" → lysosomal storage; "abundant RER" → plasma cell /
secretory; "cells with clear cytoplasm, lots of SER" → steroid-producing.
2. Nervous System & Neurophysiology
Neuron & Synapse
• Resting and graded potentials summate at the axon hillock; threshold triggers all-or-none AP.
• Saltatory conduction along myelinated axons (nodes of Ranvier). Demyelination (MS, Guillain-Barré)
slows/blocks conduction.
• Neurotransmitters: ACh, glutamate (excitatory), GABA/glycine (inhibitory), dopamine, NE, serotonin.
Key CNS Anatomy (High-Yield)
Structure Function / Lesion
Frontal lobe (prefrontal) Executive function, personality; lesion → disinhibition
Broca area (inf. frontal) Motor speech; lesion → non-fluent aphasia
Wernicke area (sup. temporal) Comprehension; lesion → fluent aphasia
Amygdala Fear/emotion; bilateral lesion → Klüver-Bucy
Hippocampus Memory formation; lesion → anterograde amnesia
Cerebellum Coordination; lesion → ipsilateral ataxia, intention tremor
Basal ganglia Movement modulation; Parkinson, Huntington
Internal capsule Lacunar stroke → pure motor hemiparesis
Spinal Tracts
• Dorsal column: fine touch, proprioception, vibration; decussates in medulla.
• Spinothalamic: pain/temperature; decussates 1–2 levels above entry.
• Corticospinal: voluntary motor; decussates at medullary pyramids.
Pearl: Brown-Séquard (hemisection): ipsilateral loss of motor + dorsal column below lesion; contralateral pain/temp
loss starting 1–2 levels below.
High-Yield Anatomy & Physiology for USMLE Step 1 • Page 3 of 20
