Interactive Simulations

Connect muscle demand to extracellular fluid, circulation, respiration, and renal support, then interrupt a link to see where the chain breaks.

Choose a regulated variable, disturbance, sensor, controller, and effector, then watch negative feedback restore the variable toward a set point.

Manipulate a pressure or concentration gradient and resistance to observe the resulting change in flow.

Assemble muscle fiber, fascicle, muscle, and connective-tissue layers while examining each layer's mechanical role.

Compare active, passive, and total tension as muscle length changes.

Change pennation angle and fiber length to explore the tradeoff between force and excursion.

Move sarcomere length through the overlap range and plot active, passive, and total tension.

Change load and contraction mode to compare concentric, isometric, and eccentric behavior.

Animate actin-myosin overlap as sarcomere length changes.

Follow sodium and potassium conductances through resting potential, threshold, depolarization, repolarization, and refractory periods.

Trace motor-neuron excitation through the end plate, excitation-activation coupling, and calcium release.

Alter extracellular sodium or potassium and observe effects on resting membrane potential and action-potential behavior.

Increase force demand and watch orderly recruitment progress from low-threshold to high-threshold motor units.

Vary stimulation frequency to display individual twitches, summation, and fused tetanus.

Combine muscle spindle and Golgi tendon organ inputs in a stretch and load feedback loop.

Compare phosphocreatine, glycolytic, and oxidative pathways by rate, capacity, and duration.

Set exercise intensity and duration to show how each ATP pathway's contribution changes over time.

Vary demand, substrate availability, and metabolite accumulation to explore declining force and power.

Compare motor-unit and fiber types by force, velocity, fatigue resistance, and metabolic strategy.

Adjust capillary hydrostatic pressure, plasma oncotic pressure, and permeability to show filtration and reabsorption.

Create venous obstruction, low plasma protein, or increased permeability and track extracellular fluid accumulation.

Change diffusion distance, gradient, and tissue demand to show oxygen delivery from capillary to muscle fiber.

Connect local metabolic signals to arteriolar smooth muscle, vessel radius, and regional flow.

Change plasma concentration, renal plasma flow, filtration, reabsorption, and secretion to calculate excretion.

Follow water, electrolytes, and acid-base inputs through filtration, reabsorption, secretion, and excretion.

Compare responses to diarrhea, sweating, adrenal insufficiency, saline infusion, high sodium intake, and SIADH.

Show how changes in renal handling alter blood volume and osmolarity over hours rather than seconds.

Change vessel radius, pressure, viscosity, and length to see why small changes in arteriolar radius have large effects on flow.

See how stroke volume creates pulse pressure while heart rate and peripheral resistance shape diastolic runoff.

Stand from supine and follow venous pooling, reduced venous return, sympathetic compensation, and pressure recovery.

Trigger widespread vasodilation and follow falling resistance, blood pressure, cerebral perfusion, and recovery after lying down.

Compare total cardiac output with the changing fractions delivered to muscle, kidney, gut, skin, and brain.

Model cuff pressure and Korotkoff sounds, including systolic and diastolic pressure detection.

Adjust preload, afterload, and contractility to observe changes in cardiac output and ventricular function curves.

Connect preload, afterload, contractility, EDV, ESV, stroke volume, and ejection fraction in a ventricular loop.

Animate atrial, ventricular, and aortic pressures alongside valve opening and closure.

Generate normal sinus rhythm and selected disturbances, then connect ECG intervals to mechanical events.

Explore why left-ventricular coronary flow changes during systole and diastole and how pressure or heart rate alters supply.

Compare actual altitude with normobaric hypoxia and match inspired oxygen pressure by changing barometric pressure or inspired oxygen fraction.

Follow partial-pressure gradients and diffusion conditions from alveolus to blood to tissue.

Shift the dissociation curve with temperature, pH, carbon dioxide, and exercise-related conditions.

Change substrate use and metabolic rate to show carbon dioxide production, transport, and respiratory exchange ratio.

Place arterial blood gas values on a map and identify respiratory and metabolic disturbances with compensation.

Set activity oxygen demand and ventilatory equivalent, then follow minute ventilation through arterial CO2 to alveolar and arterial oxygenation at altitude.

Combine tidal volume, respiratory rate, dead space, vital capacity, and functional residual capacity.

Compare minute ventilation with alveolar ventilation as dead space changes.

Relate thoracic volume, pleural pressure, alveolar pressure, and airflow during inspiration and expiration.

Compare stiff and compliant lungs while examining their pressure-volume relationships.

Explore dead space, shunt, and the alveolar-arterial gradient across different regions of the lung.

Change carbon dioxide, oxygen, metabolic demand, and voluntary control to observe the resulting ventilation response.