OUTLINE Audition Touch Smell Taste Touch Touch Hairy skin and glabrous skin hairless Layers Epidermis Dermis Subcutaneous tissue Touch Receptors mechanoreceptors Temperature Receptors thermoreceptors Mechanoreceptors of the Skin Each has unmyelinated axon branches with mechanosensitive ion channels Respond to stretching and tension e g bladder Encapsulated receptors Meissner s corpuscles Pacinian corpuscles Non encapsulated receptors Merkel s disks Ruffini s endings Receptive Fields of Sensory Receptors Relative Sensitivity More Merkel s disks and Meissner s corpuscles The two point discrimination test Receptor density Size of receptive fields Adaptation Rate Adaptation refers to length of time receptor will continue to respond to unchanging stimulus Mechanoreceptors of the Skin Free nerve endings pain and temperature Somatosensory Pathways Cranial nerves process facial sensation Touch Somatosensory Cortex Primary somatosensory cortex found in postcentral gyrus of parietal lobe Secondary somatosensory cortex found in posterior parietal lobe Primary Somatosensory Cortex S2 Further processing of touch sensation Complexity Four areas respond to different types of stimuli size shape texture movement Primary Somatosensory Cortex Plasticity of Touch Somatosensory cortex rearranges itself in response to changes in the amount of input it receives Phantom Limb Experience OUTLINE Audition Touch Smell Taste Smell Olfaction Olfactory stimuli Airborne Dissolve in mucus Olfactory Receptors 1000 receptors Olfactory epithelium Receptor cells regularly die and are replaced Odor molecule binds to cilium depolarizing neuron Olfactory and pheromone receptors McClintock Effect Pheromones sensed in the nose by vermonasal organ VNO Pheromones released during menstruation stimulates VNO in proximal women Alters hypothalamus output and induces synchronized menstruation Smell Olfactory Pathways Olfactory bulbs Glomeruli Single receptor type Olfactory tracts Olfactory cortex projects to the thalamus limbic system and neocortex OUTLINE Audition Touch Smell Taste Taste Taste begins when chemicals dissolve in the saliva of the mouth Five major classes of taste stimuli have been identified sweet sour bitter salty and umami Pain receptors sensitive to capsaicin Taste Receptors Taste receptors are contained within papillae primarily on the tongue Each papilla contains 1 100 taste buds Individual variations in number of taste buds Taste Receptors Taste buds contain 50 150 taste receptors which extend microvilli into saliva Microvilli interact with taste stimuli Taste Pathways Orbitofrontal cortex in the frontal lobe Encodes emotional qualities of taste SuperTasters 1 4 of Americans are supertasters more women 1 4 of Americans are non tasters
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