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COMLEX Level 1 • 20–25% Core Blueprint

Organ-System Physiology

Dynamic, interactive medical physiology suite: Left Ventricular Pressure-Volume Loop simulator, Nephron tubular transport & Diuretic map, Alveolar gas exchange calculator, and Endocrine axes.

Left Ventricular Pressure-Volume (PV) Loop Simulator

The PV loop depicts left ventricular mechanics through one complete cardiac cycle. Adjust preload, afterload, inotropy, and heart rate in real time, or click classic board presets (Aortic Stenosis, Aortic Regurgitation, Mitral Stenosis, Mitral Regurgitation, Heart Failure, Exercise).

Board Pathology & Hemodynamic Presets

Hemodynamic Modulators

Preload (Venous Return / EDV) 120 mL

Frank-Starling law: Shifts right boundary rightward & widens stroke volume.

Afterload (MAP / Arterial Impedance) 120 mmHg

Elevates aortic valve opening pressure & increases ESV (reduces SV).

Inotropy (Contractility / ESPVR) Normal (1.0x)

Steepens End-Systolic PV Relationship; decreases ESV and increases EF.

Heart Rate (HR) 72 bpm

Determines total Cardiac Output (CO = SV × HR).

Interactive PV Loop Diagram

Left Ventricular Pressure (mmHg) vs Volume (mL)

Normal Ref Active Loop

Point A Mitral Closes (EDV)

Point B Aortic Opens

Point C Aortic Closes (ESV)

Point D Mitral Opens

Stroke Volume 70 mL EDV - ESV

Ejection Fraction 58% (SV / EDV) × 100

Cardiac Output 5.0 L/min SV × HR

Stroke Work Normal Loop Area

Normal Baseline Hemodynamics

Normal resting adult parameters: End-Diastolic Volume ~120 mL, End-Systolic Volume ~50 mL, Stroke Volume ~70 mL, Ejection Fraction 55–65%, peak LV pressure 120 mmHg. Mitral valve closes at bottom-right (EDV), begins isovolumetric contraction. Aortic valve opens at top-right, blood is ejected until aortic valve snaps shut at top-left (ESV), initiating isovolumetric relaxation.

Nephron Segment Solute Transport & Diuretic Pharmacodynamics

Navigate tubular segments from Bowman capsule to medullary collecting duct. Inspect transporter proteins, countercurrent mechanisms, hormonal regulation, diuretic targets, and genetic channelopathies (Bartter, Gitelman, Liddle, Fanconi).

Renal Cortex

Proximal Convoluted Tubule (PCT)

65–70% of filtered Na+, H2O, Cl-, K+

Key Apical & Basolateral Transporters

Na+/H+ antiporter (NHE3), Na+/Glucose cotransporter (SGLT2), Carbonic Anhydrase (CA-IV luminal, CA-II intracellular), Na+/K+ ATPase basolateral.

Hormonal Modulation

Angiotensin II (stimulates Na+/H+ exchange → contraction alkalosis); Parathyroid Hormone (inhibits Na+/phosphate cotransporter → phosphaturia).

Target Diuretic Drug Class

Carbonic Anhydrase Inhibitors (Acetazolamide) and SGLT2 Inhibitors (Empagliflozin, Dapagliflozin).

COMLEX Exam Pearls & Pathologies

Isosmotic reabsorption occurs here (tubular fluid [TF/P] osmolality ratio = 1.0). Inulin concentration increases due to water reabsorption. Fanconi syndrome causes PCT wasting (glucosuria, aminoaciduria, hypophosphatemia, Type 2 RTA).

Master Diuretic Electrolyte & Adverse Effect Matrix

Diuretic Class	Primary Segment	Electrolyte Profile	Clinical Indications	Classic Adverse Reactions
Acetazolamide Carbonic Anhydrase Inhibitor	Proximal Convoluted Tubule (PCT)	↓ HCO3-, ↓ K+, ↑ urinary pH, normal/mild ↓ Na+	Glaucoma (decreases aqueous humor production), Altitude Sickness / AMS (produces mild metabolic acidosis to stimulate respiratory drive), Idiopathic Intracranial Hypertension (pseudotumor cerebri).	Hyperchloremic metabolic acidosis (Type 2 RTA), hypokalemia, calcium phosphate kidney stones (insoluble in alkaline urine), sulfa allergy.
Furosemide / Bumetanide Loop Diuretics (Sulfonamides)	Thick Ascending Limb (TAL)	↓↓ Na+, ↓↓ K+, ↓↓ Cl-, ↓ Ca2+ (hypercalciuria), ↓ Mg2+, ↑ HCO3- (metabolic alkalosis)	Acute Pulmonary Edema, Congestive Heart Failure, Cirrhotic ascites, Hypercalcemia (promotes calciuria), Renal failure fluid overload.	Mnemonic OH DANG!: Ototoxicity (tinnitus, hearing loss), Hypokalemia & Hypomagnesemia, Dehydration / hypotension, Allergy (sulfa), Nephritis (acute interstitial), Gout (hyperuricemia via URAT1 competition).
Ethacrynic Acid Loop Diuretic (Phenoxyacetic derivative)	Thick Ascending Limb (TAL)	↓↓ Na+, ↓↓ K+, ↓ Ca2+, ↓ Mg2+, ↑ HCO3-	Patients requiring aggressive loop diuresis who have a severe, documented sulfa allergy (e.g. anaphylaxis to sulfonamides).	More ototoxic than furosemide; hyperuricemia, hypokalemic metabolic alkalosis.
Hydrochlorothiazide / Chlorthalidone Thiazide Diuretics	Early Distal Convoluted Tubule (DCT)	↓ Na+, ↓ K+, ↑ Ca2+ (HYPERCALCEMIA / hypocalciuria), ↓ Mg2+, ↑ HCO3- (metabolic alkalosis)	Essential Hypertension (first-line), Recurrent Calcium Nephrolithiasis (reduces urinary Ca2+ excretion), Nephrogenic Diabetes Insipidus (paradoxical reduction in urine output).	Mnemonic HyperGLUC: HyperGlycemia (decreases insulin release), HyperLipidemia (elevates LDL and triglycerides), HyperUricemia (precipitates gout), HyperCalcemia. Hypokalemic metabolic alkalosis, hyponatremia.
Spironolactone / Eplerenone Aldosterone Receptor Antagonists	Cortical Collecting Tubule (Principal Cells)	↓ Na+, ↑ K+ (HYPERKALEMIA), ↓ HCO3- (mild metabolic acidosis)	Heart Failure with reduced Ejection Fraction (HFrEF - proven mortality benefit!), Primary Hyperaldosteronism (Conn syndrome), Hepatic Cirrhosis ascites, Resistant Hypertension.	Hyperkalemia (fatal arrhythmias), endocrine side effects due to cross-reactivity with androgen and progesterone receptors: Gynecomastia, decreased libido, erectile dysfunction, menstrual irregularities (Spironolactone >> Eplerenone; Eplerenone is more selective!).
Amiloride / Triamterene Direct ENaC Blockers (K+-Sparing)	Cortical Collecting Tubule (Principal Cells)	↓ Na+, ↑ K+ (HYPERKALEMIA), ↓ H+ secretion	Liddle Syndrome (constitutive ENaC activation), Lithium-induced Nephrogenic Diabetes Insipidus (Amiloride blocks lithium entry into principal cells via ENaC!), combined with loop/thiazide diuretics to prevent hypokalemia.	Hyperkalemia, metabolic acidosis. Triamterene can precipitate in tubules causing triamterene kidney stones.

Organ-System Physiology

Left Ventricular Pressure-Volume (PV) Loop Simulator

Board Pathology & Hemodynamic Presets

Hemodynamic Modulators

Interactive PV Loop Diagram

Normal Baseline Hemodynamics

Nephron Segment Solute Transport & Diuretic Pharmacodynamics

Proximal Convoluted Tubule (PCT)

Master Diuretic Electrolyte & Adverse Effect Matrix

Alveolar Gas Equation & A-a Gradient Diagnostic Engine

Alveolar Gas Equation Inputs

Calculated Results

Normal A-a Gradient (<15 mmHg)

Endocrine Negative Feedback Axes & Diagnostic Algorithms

Thyroid Feedback Axis

Adrenal Feedback Axis

Parathyroid & Mineral Axis

Interactive Physiology Board Drills

Case 1: Sudden Systolic Murmur and Pressure-Volume Loop Shift

Case 2: Arterial Blood Gas and Alveolar Gas Equation Analysis

Case 3: Severe Hypertension, Hypokalemia, and Undetectable Renin/Aldosterone

Organ-System Physiology

Left Ventricular Pressure-Volume (PV) Loop Simulator

Board Pathology & Hemodynamic Presets

Hemodynamic Modulators Reset to Normal

Interactive PV Loop Diagram

Normal Baseline Hemodynamics

Nephron Segment Solute Transport & Diuretic Pharmacodynamics

Proximal Convoluted Tubule (PCT)

Master Diuretic Electrolyte & Adverse Effect Matrix

Alveolar Gas Equation & A-a Gradient Diagnostic Engine

Alveolar Gas Equation Inputs

Calculated Results

Normal A-a Gradient (<15 mmHg)

Endocrine Negative Feedback Axes & Diagnostic Algorithms

Thyroid Feedback Axis

Adrenal Feedback Axis

Parathyroid & Mineral Axis

Interactive Physiology Board Drills

Case 1: Sudden Systolic Murmur and Pressure-Volume Loop Shift

Case 2: Arterial Blood Gas and Alveolar Gas Equation Analysis

Case 3: Severe Hypertension, Hypokalemia, and Undetectable Renin/Aldosterone

Hemodynamic Modulators