Sensory transduction: vision, audition, somatosensation, chemosensation, proprioception.
Sensory Physiology
Sensory transduction
Conversion of physical/chemical stimulus to neural signal by specialised receptor cells. Common theme: stimulus → receptor protein →…
Phototransduction
Vertebrate rod/cone signalling: photon → 11-cis-retinal → all-trans-retinal → opsin activates transducin → PDE hydrolyses cGMP → CNG…
Photoreceptor (rod / cone)
Retinal sensory neurons. Rods (~120M): high sensitivity, scotopic, rhodopsin only, no colour. Cones (~6M): lower sensitivity, photopic,…
Cochlear hair cell
Mechanoreceptor in the organ of Corti. Stereocilia deflection opens tip-link-coupled K+ channels, depolarises cell, triggers glutamate…
Chemosensation
Taste (gustation): GPCR-mediated sweet/bitter/umami + ion-channel salty/sour. Smell (olfaction): ~400 OR GPCRs in humans, combinatorial…
Nociception
Sensing of tissue-damaging stimuli. Free nerve endings with TRPV1 (heat, capsaicin), TRPA1 (chemical irritant), ASIC (acid), Piezo2…
Olfaction
~400 functional olfactory receptors (GPCR) in humans; Buck & Axel 1991. Combinatorial coding: each odorant activates multiple receptors.…
Gustation (taste)
Five basic tastes: sweet, bitter, salty, sour, umami. T1R/T2R GPCRs + ENaC/PKD2L1 channels. Taste buds on papillae → chorda…
Mechanotransduction
Mechanosensitive ion channels (Piezo1/2) convert force to current. Touch, proprioception, hearing, baroreception. Patapoutian Nobel 2021.
Vestibular system
Semicircular canals sense rotational acceleration; otolith organs (utricle, saccule) sense linear + gravity. Integrates with vision +…
Stevens psychophysics power law
Stevens 1957: perceived intensity S = k I^n where exponent n depends on modality (loudness 0.67, brightness 0.33, electric shock 3.5). …
Signal detection theory & ROC
Tanner-Swets 1954: SDT separates sensitivity d' = (μ_S - μ_N)/σ from criterion β; observer chooses decision threshold to balance…
Rhodopsin (Stryer 1991)
L Stryer 1991 rhodopsin G-protein cascade; modern Hofmann 2009 rhodopsin-receptor superfamily; phototransduction model.
Cochlea (Bekesy 1928)
G von Bekesy 1928 (Nobel 1961) traveling-wave; modern outer-hair-cell electromotility prestin Liberman 2002.
Olfaction (Buck-Axel 1991)
Buck-Axel 1991 (Nobel 2004) ~1000 olfactory-receptor genes; modern combinatorial-coding + glomerular-mapping.
Taste (Ryba-Zuker 2000)
N Ryba-C Zuker 2000s T1R/T2R taste-receptors + Trpm5 + ENaC; 5 modalities sweet/sour/salty/bitter/umami.
Touch (Julius-Patapoutian 2021)
Julius-Patapoutian Nobel 2021 TRPV1 + Piezo1/2 mechano + thermosensation; modern Piezo channelopathies.
Proprioception (Sherrington 1906)
C Sherrington 1906 'Integrative Action of the Nervous System' (Nobel 1932); muscle-spindle + Golgi-tendon; modern Piezo2 mechano.
Hartline (Nobel 1967)
H Hartline 1967 (Nobel 1967) lateral-inhibition limulus; modern modern foundational text + Mach-bands + 2024 retinal-circuit-disorder…
Rhodopsin (Wald 1967)
G Wald 1967 (Nobel 1967) rhodopsin-vision; modern modern foundational + opsin-cryoEM + 2024 GPCR-orphans deorphanization olfactory + bitter.
Olfactory receptor (Buck-Axel 1991)
L Buck-R Axel 1991 (Nobel 2004) olfactory-receptor; modern modern foundational + 100k-glomeruli + 2024 ML-OR-deorphanization odor-pred.
TRP (Julius 2003)
D Julius 2003 (Nobel 2021) capsaicin-TRPV1; modern modern foundational + Patapoutian Piezo + 2024 mechanosensation drug-targets pain.
Electroreception (Bullock 1972)
T Bullock 1972 + Heiligenberg fish-electroreception; modern modern foundational + 2024 platypus + dolphin + shark ampullae-of-Lorenzini…
Hair cell (Hudspeth 1979)
A J Hudspeth 1979 hair-cell-mechanotransduction; modern modern foundational text + 2024 TMC1/2 Patapoutian-channel + presbycusis aging.