Nerves & Senses
How a nerve signal is made and passed on, and what the senses do with it: the action potential, the synapse, the neuromuscular junction and the reflex arc, then vision, hearing, balance, taste, smell and pain. The signalling chemistry sits here as well — dopamine, serotonin, GABA, adenosine — along with what changes in stroke, seizure and migraine.
Every page here is a hands-on animated diagram, not a video — press play, slow it down, break the mechanism on purpose, and read the live values in real clinical units. They explain how a process works; they are not medical advice, and the evidence for any treatment lives on the topic pages each animation links into.
Table of Contents
The Animations (24)
Why Chili Burns: Capsaicin & the TRPV1 Heat Sensor
Discover that chili isn’t hot — it hijacks your heat receptor to fake a burn — then reach for water and fail, milk and succeed, and see how the same trick turns nerve pain down in a capsaicin cream.
Launch animation →Caffeine, Adenosine & Why Coffee Stops Working
Caffeine doesn't give you energy — it blocks the tiredness signal while it keeps piling up behind the blockade. Move your coffee to 2 p.m. and watch your deep sleep disappear.
Launch animation →Nerve Impulse
Fire an action potential and watch it race down the axon — sodium rushing in, potassium out, a live voltage trace spiking, and neurotransmitter crossing the synapse.
Launch animation →Pain, the Gate Control & Why Rubbing Helps
Fire a pain signal up the spinal cord — then rub the skin and watch the gate close, or release endorphins and see the same signal fade before it ever reaches the brain.
Launch animation →Taste: The Five Basic Tastes & How Your Tongue Reads Them
Fire each of the five tastes and watch its own molecular trick — sweet, bitter and umami through G-protein receptors, salty and sour through ion channels — then discover that ‘spicy’ is pain, not taste, and the tongue map is a myth.
Launch animation →The Reflex Arc: Faster Than Thought
Tap the tendon and watch the signal fire into the spinal cord and straight back out to the muscle in about 50 milliseconds — while the brain only finds out afterward. The knee-jerk isn’t your brain reacting fast.
Launch animation →Serotonin, Mood & SSRIs
Build serotonin from tryptophan, fire it across the synapse, and vacuum it back with SERT — then take an SSRI and watch the cleft flood, or starve the tryptophan and watch the signal fade.
Launch animation →What Happens in a Seizure
Tip the balance between excitation and inhibition and watch neurons fire in a runaway synchronous storm — then see how the seizure spreads and how medication damps it back down.
Launch animation →How the Eye Focuses: Near, Far & Why You Need Glasses
Watch the lens flatten for distance and round up for near reading — then make the eye too long for myopia or stiffen the lens with age, and slot in the exact lens that fixes each.
Launch animation →The Blood-Brain Barrier: The Brain’s Bouncer
Send molecules at the tightest wall in the body — watch fat-soluble ones slip through, big ones bounce, and a pump eject the rest — then see why L-DOPA gets in when dopamine can’t, and how meningitis breaks the gate.
Launch animation →How Memories Form: Synaptic Plasticity (LTP)
Watch two neurons that fire together wire together — the NMDA receptor detects the coincidence, calcium floods in, and the synapse strengthens into a memory — then block it with alcohol and watch the memory fail to form.
Launch animation →Dopamine, Reward & How Habits Hijack You
Dopamine is not the pleasure chemical. Watch the spike migrate from the reward to the cue, then withhold the reward and see it dip below zero — that dip is craving.
Launch animation →How Drug Tolerance & Dependence Develop
Watch a neuron pull receptors off the surface so a drug does less and less — tolerance — then stop suddenly and see everything rebound the opposite way into withdrawal, and taper slowly to recover safely.
Launch animation →The Gut-Brain Axis: How Your Gut Talks to Your Brain
Follow the vagus nerve carrying signals up from your gut to your brain, the gut making most of your serotonin, and the microbiome shaping mood — then flip it and watch stress disrupt the gut.
Launch animation →Cerebrospinal Fluid: The Brain’s Cushion & Plumbing
Make CSF at the choroid plexus and follow it around the brain and spine and back to the blood — block the aqueduct to flood the ventricles (hydrocephalus), or fall asleep and watch the glymphatic system flush the brain’s waste.
Launch animation →GABA: The Brain’s Brake
Watch glutamate try to fire a neuron while GABA slams the chloride brake on — then add a benzodiazepine or alcohol and see the brake amplified, and why stacking them is dangerous.
Launch animation →What Happens in a Stroke
Block a brain artery and watch the core die while the penumbra flickers on the edge — then reopen the clot and see why 'time is brain' means roughly 1.9 million neurons lost per minute.
Launch animation →The Pupil: Your Eye’s Aperture & the Light Reflex
Shine a light and watch both pupils snap shut together — the consensual reflex — then dim the room to open them, and see why a doctor’s penlight can reveal a brainstem emergency or an opioid overdose.
Launch animation →Vision & the Retina
Focus light through the lens onto an inverted retinal image, then follow the phototransduction cascade as rods and cones react — dim the lights and watch the eye adapt.
Launch animation →What Happens in a Migraine
Ride the slow wave of cortical spreading depression across the cortex, watch the trigeminal nerve dump CGRP and inflame the meninges — then block CGRP and calm the throb.
Launch animation →Balance & the Inner Ear: Vertigo & BPPV
Turn and tilt your head and watch the inner-ear canals and otoliths fire your sense of balance — then knock a crystal loose to trigger BPPV vertigo, and roll it back out with the Epley manoeuvre.
Launch animation →The Neuromuscular Junction: How a Nerve Commands a Muscle
Fire a nerve and watch calcium dump acetylcholine across the gap to spark the muscle — then block it with Botox, strip the receptors in myasthenia gravis, or jam the off-switch with a nerve agent.
Launch animation →Smell: How Your Nose Reads a Trillion Odours
Send an odour at your ~400 receptor types and watch a unique pattern light up — how you smell a trillion things with a few hundred sensors, why smell hooks straight into memory, and why losing it warns of Parkinson’s.
Launch animation →Hearing & the Cochlea
Send a sound wave through the eardrum and ossicles into the cochlea, and slide the frequency to see the traveling wave peak land on its tonotopic place — and now actually hear the pitch you set.
Launch animation →