All courses · advanced elective
Sensory Systems
An advanced elective that follows the Neuroscience course. It starts where the textbook account of each sense ends: the genetically defined cell types of the skin, retina, ear, nose and gut, the channels that turn force, heat and chemicals into current, and the circuits that first read them. It covers touch and its receptors in depth, temperature, pain and itch, proprioception and sensing the body from inside, vision, hearing and balance, smell and taste, and ends with how the senses are combined, predicted and restored by prostheses.
8 units · 30 lessons
Unit 1 · Transduction and sensory cell types
- Unit 1: Transduction and sensory cell types Five Ways to Turn a Stimulus into a Current The famous 40 microseconds of hair-cell transduction was never the opening time of a channel. What was it?
- Unit 1: Transduction and sensory cell types Piezo Channels and the Physics of Force A channel shaped like a shallow dome, 28 nm across. Flatten it and it opens.
- Unit 1: Transduction and sensory cell types Sensory Neurons by Their Genes: the Atlas Era One mouse data set found eleven kinds of touch, pain and itch neuron; a later one found seventeen. Which number is right?
Unit 2 · Touch
- Unit 2: Touch The Low-Threshold Mechanoreceptors On a mouse's back, an awl/auchene hair follicle is fenced by the endings of three different kinds of touch neuron. Why build a sense that way?
- Unit 2: Touch Merkel Cells: Touch Receptors That Are Not Neurons A skin cell that is not a neuron fires calcium spikes when pressed. What is it telling the nerve?
- Unit 2: Touch Meissner and Pacinian Corpuscles: Flutter and Vibration Strip the outer onion layers off a Pacinian corpuscle and its terminal, still wrapped by inner-core cells, adapts in milliseconds, in duck recordings from 2025. So what is the capsule for?
- Unit 2: Touch Hairy Skin, Stroking and Affective Touch Brush a forearm at a few centimetres per second and one slow, unmyelinated fibre fires hardest. Is that why it feels nice?
- Unit 2: Touch Where Touch Is First Processed: Dorsal Horn and Dorsal Column Nuclei A touch signal that reaches the brainstem has often been through the spinal cord's circuitry first. What does that circuitry do to it?
- Unit 2: Touch Touch Over-reactivity in Autism Models In one experiment, deleting a gene from peripheral sensory neurons, but not from the brain, was enough to change a mouse's behaviour in anxiety-like and social assays.
Unit 3 · Temperature, pain and itch
- Unit 3: Temperature, pain and itch Hot, Warm, Cool and Cold Mice lacking the cold-and-menthol receptor TRPM8 failed completely to learn to report forepaw warming in a 10-day task. Why would a cold receptor matter for warmth?
- Unit 3: Temperature, pain and itch Nociceptors and the Sodium Channels of Pain Three families in which nobody could feel pain pointed to one sodium channel. Twenty years later, the drug that reached patients blocks a different one.
- Unit 3: Temperature, pain and itch Spinal Circuits That Gate Pain A gate can fail because the gatekeeper dies, or because the gatekeeper is still there and its signal has changed sign. In adult male rat lamina I, nerve injury was shown to do the second.
- Unit 3: Temperature, pain and itch Itch: A Sense of Its Own A mouse missing one cluster of Mrgpr genes scratches normally to histamine but much less to chloroquine. Which parts of the itch pathway are shared with pain, and which are not?
- Unit 3: Temperature, pain and itch When Pain Persists Silence one group of amygdala neurons in a mouse with nerve injury and the paw still withdraws, yet the escape and avoidance fall away. What does that say about where pain lives?
Unit 4 · Proprioception and interoception
- Unit 4: Proprioception and interoception Proprioception: Sensing the Body's Own Position Vibrate a tendon at 100 Hz and a person with their eyes closed misjudges the position of the elbow, by as much as 40 degrees when the muscle is contracting.
- Unit 4: Proprioception and interoception Vagal Sensory Neurons: The Body Reports to the Brain Light on one set of vagal sensory axons stops an anaesthetized mouse breathing, and light on another set makes it breathe fast and shallow. What does each set report, and how would you know?
- Unit 4: Proprioception and interoception Sensing the Gut: Enteroendocrine Cells and Nutrient Signals A mouse with no sweet taste still learns to prefer sugar over a sweetener. The sensor is in its gut, and it is not a neuron. How would you show that?
Unit 5 · Vision
- Unit 5: Vision Forty Kinds of Ganglion Cell Four careful censuses of mouse ganglion cells gave 32, 35, 42 and 46. Who is right?
- Unit 5: Vision Computing Motion in the Retina A cell in the eye fires to a spot moving left and stays quiet for the same spot moving right. Which neuron makes the difference?
- Unit 5: Vision Melanopsin Cells: Seeing Without Images A mouse with no working rods or cones can still tell a striped screen from a grey one. Which cells are doing the seeing?
- Unit 5: Vision Photoreceptors Across a Billion-Fold Range, and When They Fail Delete both calcium sensors from a mouse cone and the cone still adapts to background light. What is left doing the work?
Unit 6 · Hearing and balance
- Unit 6: Hearing and balance The Hair Cell's Transduction Channel A gene is required for hearing, and its protein sits at the right place. What else must be shown before it counts as the channel?
- Unit 6: Hearing and balance The Cochlear Amplifier and Otoacoustic Emissions A microphone sealed in your ear canal can record sound that your own cochlea made. What does that sound tell us about the amplifier, and what can it not tell us?
- Unit 6: Hearing and balance Hidden Hearing Loss, Gene Therapy and Regeneration A mouse can pass its hearing test after loud noise and still have lost about half the ribbon synapses at one place in the cochlea. What does a normal threshold actually tell you?
- Unit 6: Hearing and balance Balance: Vestibular Hair Cells and Self-Motion Mature mouse type I hair cells still drove their afferent's spikes when vesicle release was crippled. What carries the signal?
Unit 7 · Smell and taste
- Unit 7: Smell and taste One Receptor per Neuron: How Olfactory Neurons Choose A mouse olfactory neuron holds about a thousand receptor genes and uses one copy of one. How does it choose, and why can it not change its mind?
- Unit 7: Smell and taste From Glomeruli to Piriform Cortex Two mitral cells share one glomerulus and fire at the same average rate, yet disagree about when. What does the cortex do with that disagreement?
- Unit 7: Smell and taste Taste from Tongue to Cortex A type II taste cell has no axon and no synaptic vesicles, yet it talks to a nerve fibre in milliseconds. How?
Unit 8 · Integration and repair
- Unit 8: Integration and repair Combining Senses and Predicting Them You cannot tickle yourself, yet a mouse's Pacinian afferents fire strongly to its own movements. Where does the cancellation happen?
- Unit 8: Integration and repair Restoring Senses: Implants, Prostheses and Optogenetic Vision A cochlear implant has up to 22 contacts, yet listeners can plateau near 8 to 10 channels. What counts as a channel?