LectNeuro - Information Processing Two objectives: How...

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Information Processing Two objectives: • How information is processed • Specific receptor capabilities, sensory systems
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General Considerations • Capacity for obtaining, coordinating information essential part of natural selection • Environments not constant; change over time • Animals must detect changes: adapt or move • Need for complex sensory systems related to: – increase in size – specialization • Stable internal environment invasion of harsher environments constant surveillance
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Please begin reading assigned pages in Chapters 2, 3 and 4 Remember the context
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General Considerations Increased need for: • sensory information about environment • information about other parts of body • carriers of information to an analyzing center ( peripheral nervous system ) • integration of information ( central nervous system )
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environment perception
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Nature of Information • presence or absence • modality (quality of a stimulus) 9 e.g., sight, smell, sound, etc. • amplitude (intensity & modulation) • duration • timing of stimuli relative to one another • rate of onset and decay (change) • complexity
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Information Normally carried in one of 2 ways: active chemical – single cells or hormones nervous system – faster, highly specific
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Functional Units of Nervous System Neuron (dendrites, cell body, axon) (see text) Receptor • a structure that receives an environmental stimulus stimulus is a quality of the environment that excites a receptor • stimulus goes no farther than the receptor receptor = transducer
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Functional Units of Nervous System Two categories of receptors: Primary receptor: free nerve ending Secondary receptor: specialized cells other than nerve cells • E.g., rods and cones of eye “Adequate Stimulus” : Particular form of energy to which a receptor has evolved sensitivity
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Electrical Events of Information Processing Please review conventions of electrical terminology Potential: separation of charge Current: flow of charge
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Resting or Rest Potential • characteristic of all cells • occurs across the cell membrane, not within the cytoplasm • sign and size of the potential difference across the membrane is determined by its relative permeability to the principal inorganic ions: Na, K, Cl and Ca • membrane permeability is low, but selective for specific ions
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Resting or Rest Potential Ranges from – 4 to –100 mV Nerve – 70 mV Skeletal muscle – 90 mV Smooth muscle – 40 mV
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Gibbs-Donnan Equilibrium • All cells enclosed by selectively permeable membrane and contain large quantities of proteins too large to penetrate membrane • Smaller diffusible ions tend to distribute across the membrane in manner that compensates for net negative charge inside membrane: K + predominantly inside; Cl - predominantly outside • Non-diffusible charge asymmetric (unequal) distribution of ions
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P K + Cl - K + Cl -
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