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Unformatted text preview: Lecture 9 SmartSite: Lecture 9 Notes Announcements: None Review Sensory Systems Somatosensory system The Ear Auditory system Reading (Recommended): Relevant por;ons of Chapter 6 1 REV: Receptors Afferent arm of PNS Receptors transduce sensory s;muli Classified by type or loca;on of s;muli Transduc;on s;mulus energy to Em change Receptor cell vs. Receptor neuron Receptor adapta;on Tonic = s;mulus level Phasic = s;mulus change 2 Somatosensory System 3 Recep;ve Field (Acuity) Fig. 6-6, pg. 189 4 Lateral Inhibi;on (Acuity) Several receptors respond to a s;mulus, while others do not Lateral inhibi;on increases contrast between responsive versus the uns;mulated receptors Fig. 6-7a, pg. 190 5 Lateral Inhibi;on Fig. 6-7, pg. 190 6 Labeled Line Coding Pathways conveying conscious soma;c sensa;on Consists of chains of neurons, or labeled lines, synap;cally interconnected in par;cular sequence to accomplish processing of sensory informa;on First-order sensory neuron Afferent neuron with its peripheral receptor that first detects s;mulus Synapses on Second-order neuron Either in spinal cord or medulla Synapses with third-order neuron Located in thalamus Pathways conveying conscious soma;c sensa;on consists of chains of neurons, or labeled lines, synap;cally interconnected in par;cular sequence to accomplish processing of sensory informa;on First-order sensory neuron Afferent neuron with its peripheral receptor that first detects s;mulus Synapses on Second-order neuron Second-order sensory neuron Third-order sensory neuron Second-order sensory neuron Either in spinal cord or medulla Synapses with third-order neuron Third-order sensory neuron Located in thalamus 7 Modality or type of informa;on 8 The Somatosensory Cortex Fig. 5-10a, pg. 148 9 Sensory Homunculus Some body regions have greater representa;on More cortex devoted to processing s;muli from that region Fig. 5-10b, pg. 148 10 Integra;on of Sensory Informa;on 1. Modality or type of sensory informa;on 2. Receptor type 3. AP firing rate of afferent propor;onal to s;mulus intensity 4. Rate of receptor adapta;on 5. Number of afferents firing 6. Receptor density / Receptor field size 7. Lateral inhibi;on 8. Labeled line coding 11 The Ear (Auditory & Ves;bular) 12 Ear Consists of three parts External ear Consists of pinna, external auditory meatus, and tympanum Transmits airborne sound waves to fluid-filled inner ear Amplifies sound energy Transmits airborne sound waves to fluid-filled inner ear Amplifies sound energy Houses two different sensory systems Middle ear Inner ear Cochlea Contains receptors for conversion of sound waves into nerve impulses which makes hearing possible Ves;bular apparatus Contains receptors for conversion of accelera;on into nerve impulses which is important for sense of equilibrium 13 Ear - Auditory Fig. 6-32, pg. 215 14 Audi;on - Hearing What is the auditory system? Neural percep;on of sound energy Sound waves Iden;fica;on of the sounds ("what") Localiza;on of the sounds ("where") Informa;on is processed in the brain by resynthesizing the frequency & amplitude components conveyed by the receptor generated APs 15 Traveling vibra;ons of air Consist of alternate regions of compression and rarefac;on of air molecules Broken down to frequency and amplitude components by the receptors of the inner ear Forma;on of Sound Waves Fig. 6-33, pg. 215 16 Proper;es of Sound Waves Fig. 6-34, pg. 216 17 Sound Wave Transmission Tympanic membrane vibrates when struck by sound waves Middle ear transfers vibra;ons through ossicles (malleus, incus, stapes) to oval window (entrance into fluid-filled cochlea) Pressure waves in cochlear fluid set basilar membrane in mo;on Recep;ve hair cells are bent as basilar membrane is deflected up and down Mechanical deforma;on of specific hair cells is transduced into neural signals that are transmifed to auditory cortex in temporal lobe of brain for sound percep;on 18 Sound Wave Transmission Fig. 6-36a, pg. 219 19 Transmission of Sound Waves Fig. 6-36bc, pg. 219 20 ...
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- Spring '08