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 +…