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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 Æ 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 Æ 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 Æ 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 Merkel’s disks, Meissner’s Corpuscles, and Oacinian Corpuscle...
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This note was uploaded on 04/07/2008 for the course ES/OT 343 taught by Professor Youakim during the Spring '07 term at SUNY Buffalo.
- Spring '07