chapt45_lecture - CHAPTER 45 NEUROSCIENCE III: SENSORY...

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1 CHAPTER 45 NEUROSCIENCE III: SENSORY SYSTEMS
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2 Sensory transduction Incoming stimuli (chemical or physical stimuli from an animal’s body or the external environment) are converted into neural signals Perception Awareness of sensations Not all sensations are consciously perceived by an organism Sensory receptor Recognizes stimulus and initiates signal transduction by creating graded potentials in the same or adjacent cells Either neurons or specialized epithelial cells When the response is strong enough and action potential is sent to the CNS
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3 Strength/type of stimulus Strength of the stimulus is indicated by the frequency of action potentials generated Strong stimulus generates more action potentials in a shorter amount of time Brain interprets higher frequency of action potentials as a more intense stimulus Different stimuli produce different sensations because they activate specific neural pathways that are dedicated to processing only that type of stimulus
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4 Strength of the stimulus is indicated by the frequency of action potentials generated Strong stimulus generates more action potentials in a shorter amount of time
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5 Receptor types Mechanoreceptors transduce mechanical energy Thermoreceptors – respond to cold and heat Nociceptors, or pain receptors – respond to extreme heat, cold, and pressure, as well as to certain molecules such as acids Electromagnetic receptors – detect radiation within a wide range of the electromagnetic spectrum Photoreceptor s – respond to visible light Chemoreceptors respond to specific chemicals
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6 Skin receptors Meissner’s corpuscles Sense touch and light pressure Lie just beneath skin surface Pacinian corpuscles Located much deeper beneath the surface Respond to deep pressure and vibration Mechanoreception Some mechanoreceptors are neurons Others are specialized epithelial cells
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7 Stretch receptors - mechanoreceptor Stretching deforms them They depolarize Send action potentials to the brain Stretching in stomach is interpreted as fullness Stretching in blood vessels provides blood pressure information Found in the walls of organs like stomach and bladder
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8 Hair cells- mechanoreceptors are specialized epithelial cells , called hair cells. Specialized epithelial cells Deformable cilia resemble hairs Ion channels open or close when cilia bend which changes membrane potential Found in the ear and equilibrium organs , body surface of fish and some amphibians
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9 Lateral line system Hair cells that detect changes in water currents Cilia of hair cells protrude into cupula within lateral line system When cupula moves, cilia bend, and neurotransmitter released
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10 Audition Ability to detect and interpret sound waves Wavelength – distance from the peak of one wave to the next Frequency – number of complete wavelengths in a second (Hz) Short wavelengths have high frequencies perceived as high pitch or tone Long wavelengths have lower frequencies perceived as a lower pitch
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This note was uploaded on 04/10/2008 for the course BIO 3000 taught by Professor Joseph during the Spring '08 term at St. Johns Duplicate.

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chapt45_lecture - CHAPTER 45 NEUROSCIENCE III: SENSORY...

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