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Unformatted text preview: Study Guide for Neuroscience Exam 1 Sensory Systems Overview Transduction: Sensory receptors convert physical energy into electrical activity in the nervous system Types of Receptors and examples of each: o Exteroceptors- Environment outside body (5 senses) o Interoceptors- Within the body Proprioceptors and receptors of the vestibular system o Mechanoreceptors Somatosensory and auditory o Chemoreceptors Taste, olfaction, and pain o Photoreceptors Vision o Thermoreceptors Somatosensory Characteristics of Receptor Potentials o A change in the voltage across the receptor membrane o Particular physical energy causes a change in membrane permeability o In sensory transduction a particular physical energy causes a change in the receptor membrane permeability to some ions and a change in membrane potential Can be depolarizing (touch), hyperpolarizing (photoreceptors), or both (auditory) This depends on the type of receptor that is involved Usually involved Na+ Channels open receptor potential depolarizes o Graded potentials depend on the intensity of the stimulus If the recepetor potential is strong enough, there will be a change in AP firing of the primary afferent neuron (1 st order afferent or ganglion) Nuclei of the Sensory Thalamus o Medial Geniculate Nucleus: Auditory Nucleus o Lateral Geniculate Nucleus: Visual Fibers o Ventral Posterior Nucleus: Somatosensory Nucleus Examples of the Labeled Line Phenomenon o Homunculus in somatosensory cortex: Penfields Demonstration He stimulated different parts of the cortex and ask patients what sensations they felt throughout the body o Nerve Compression Ulnar n. trauma (funny bone) o Phantom Limb Pain Pain in part of body you no longer have Synesthesia-sensations coming together sensations gives rise to more than 1 sense o Taste gives sensation of touch in hand Stimulus Localization o Receptive Field The smaller the receptive field, the greater the precision in localizing a stimulus o 2 Point discrimination test to test for sensitivity o Lateral Inhibition A mechanism for increasing precision in localizing stimuli Occurs because a reciprocal inhibitory connections between adjacent neurons This helps enhance contrast and encodes what a stimulus is Inhibits Neighbors More precise location Main goal is to provide an exact replica Shape is most important in perception Somatosensory System I: Tactile Dorsal Root Ganglion Cells (DRG Cells) o For all modalities DRG cells are the 1 st order afferent o Transmit Somatosensory information from limbs and trunk Tactile Receptors and Characteristics o Glabrous skin (fingers and toes) has complex and dense array of receptors and consequently the skin here is very sensitive compared to hairy skin o Receptors are either free nerve endings (pain) or nerve endings surrounded by a capsule of non- neural tissue) o Merkels disks, Meissners Corpuscles, and Oacinian Corpuscle...
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- Spring '07