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Published byWalter Lucas Modified over 8 years ago
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Electrical signals Sodium ions Potassium ions Generate an action potential at the axon hillock Travels down the axon to the terminal – regenerating the action potential in each portion of the membrane
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synapse
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neurotransmitters Chemical signals released by presynaptic neurons Bind to receptors on postsynaptic neuron or effector cells Stimulate or inhibit them 50+ different molecules have been identified Classified chemically and functionally
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Other examples Histamine GABA Glutamate Glycine Endorphins
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Postsynaptic membrane receptor Receive neurotransmitter Specialized to open/close ion channels Produces graded local change to membrane potential/voltage according to amount of NTM released and time it sticks around
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Types of synapses Where the axon synapses with the postsynaptic cell Graded potentials dissipate in strength as spread – most effective type of synapse?
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Effects Excitatory Synapses Depolarization (more +) of postsynaptic membrane Channels allow Na+ and K+ ions to diffuse simultaneously Local graded depolarization = EXCITATORY POSTSYNAPTIC POTENTIAL (EPSP) Helps trigger an action potential Inhibitory Synapses Induce hyperpolarization (more -) of postsynaptic membrane More permeable to K+, Cl- or both Less likely to “fire” an action potential, or requires a larger depolarizing current INHIBITORY POSTSYNAPTIC POTENTIAL (IPSP)
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Neural integration Reflects sum of all incoming neural information received Both stimulatory and inhibitory inputs Axon hillock keeps a running account of all the signals it receives
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modeling Seekers: must find the right message Neuron chain, standing hand to hand – once stimulated, must pass the message from one person to the next until reaches axon hillock. Axon hillock: keeps a running total of the charge
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Problem solve: how do you get your message to “win”? Must adhere to the same rules…but can alter everything else
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Summation: add together to influence activity of post-synaptic neuron temporal 1 or more presynaptic neurons transmit impulses in rapid-fire order Quick succession, before signal dissipates spatial Postsynaptic neuron stimulated by a large number of terminals from same or different neurons at the same time Large number of receptors bind neurotransmitters
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