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Review: Neural Communication
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Resting Cell Charges KW 4-10
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Depolarization KW 4-11 A Graded Potential
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Hyperpolarization KW 4-11 A Graded Potential
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Phases of the action potential K&W 4-14
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Reversal of Charges Cell body end of axon Direction of neural impulse: toward axon terminals
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Falling dominos K&W p. 131
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Ion flow K&W 4-15
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Properties of Action Potentials All or none: fires completely or not at all Self-propagates: recreates itself Does not degrade: doesn’t lose power Full strength to the end of axon Axon can be any length
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Naked Neurons Neurons without myelin sheath Slower Shorter Can’t carry messages long distances What does myelin sheath provide?
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Nodes of Ranvier K&W 4-16
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Saltatory conduction K&W 4-17 Saltare = to jump Action potential skips from node to node
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Multiple Sclerosis Jacqueline Du Pre 1945-1987 MS diagnosis in 1971 Hilary and Jackie (1998 movie)
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Neuronal Integration To fire or not to fire, that is the question All or none principle: all or nothing at all Why important?
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Firing Line
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Threshold
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Sherrington Sir Charles Scott Sherrington (1857-1952) Withdrawal reflex Principle of summation Nobel prize in medicine 1932
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Withdrawal Reflex in Dogs One mild pinch between toes no response Two pinches quickly in same spot withdraw paw Temporal Summation Temporal = over time
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Paw reflex: part 2 One mild pinch in one location no response Two pinches in different locations withdraw paw Spatial Summation Spatial = over space
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Temporal: one location KW 4-19 Excitatory Postsynaptic Potential Presynaptic cell sensory Postsynaptic cell motor synapse
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Temporal EPSP KW 4-19 top
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Spatial: more than one location K&W 4-20
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Spatial EPSP KW 4-19
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Importance of EPSP Excite cells Bring about activity Sensation felt Muscle moved
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Excitation must be balanced Nervous system can’t run on just excitation Sometimes better not to respond Role on inhibition Calm down the nervous system
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Role of Inhibition Provides break for the nervous system Lowers activity levels Keeps the brain from over-excitation, as in epilepsy
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EPSP and IPSP K&W 4-18 Inhibitory Postsynaptic Potential
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Temporal IPSP KW 4-19
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Temporal Combos
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Spatial Combos
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A cell decides to fire K&W 4-21 Democracy of Cells
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Emotional Arousal Autonomic nervous system controls physiological arousal Sympathetic division (arousing) Pupils dilate Decreases Perspires Increases Accelerates Inhibits Secrete stress hormones Parasympathetic division (calming) Pupils contract Increases Dries Decreases Slows Activates Decreases secretion of stress hormones EYES SALIVATION SKIN RESPIRATION HEART DIGESTION ADRENAL GLANDS
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Control over heart Sympathetic excites Parasympathetic inhibits Work together to control heart
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