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BIO271H1 (40)

The lecture where she decided to post ONLY pictures

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Melanie Woodin

B271 Lec 4 Mechanoreceptors y Two main types of mechreceptor proteins enac and trp channels y Free Nerve Endings and Merkels DisksMerkels disks are free nerve endings associated with an enlarged epidermal cell They have small receptive fieldswhat are they used for Slowly adapting tonic receptors most sensitive to indentation of the skinslide 6 nerve endings that are wrapped around the base of a hair follicle monitor y Root Hair Plexusmovements across the body surface Rapidly adapting phasic receptors most sensitive to changes in movementie a bug crawling on your skin y Slide 8 Rapid adaptation by the pacinian corpuscle is a good example of mechanical filtering by accessory structures The PC is a pressure and vibration receptor found deep in the skin muscle tendons and joints A sensory dendrite wrapped in layers of connective tissue y With the corpuscle intact the neuron depolarized transiently at the onset and offset of the stimulus W the accessory layers removed the neuron remained depolarized during most of the stimulus How do the acclayers produce sensory adaptation The layers of the corpuscle preferentially pass on rapid changes in pressure while filtering out prolonged steady pressure Critical in sensory neuron adaptationslide 9 y Vertebrate Proprioceptorso Muscle spindles are located in skeletal muscles Monitor muscle length o Golgi tendon organs are located in tendons Monitor tendon tension o Joint capsule receptors are in capsules that enclose joints and monitor pressure tension and movement y Insect Tactile Receptors because insects are encased in a hard exoskeleton their sense of touch cannot function via free nerve endings instead they use sensillao Two common types of sensilla Trichoid y Hairlike projection of cuticle y Bipolar sensory neuron y TRP channelCampaniform y Dome shaped bulge of cuticle near joints y Coordinate movement o Slide 12 Longitudinal section through a mechanoreceptor of DrosophiliaCutting the shaft allows electrical access to the sensory neuronMechanical distortion activates ion channels which produced the receptor potentialThe dendrite is bathed in endolymph which has a high concentration of K When the bending of the shaft opens stretch activated cation selective channels there is an inward driving force for K
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