Nervous_System_pdf - Nervous System Wh Why do animals need...

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Nervous System
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Why do animals need a nervous system? ± What characteristics do animals need in a nervous system? ² fast ² accurate ² reset quickly Remember… think about the bunny… Poor bunny!
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ervous system cells Nervous system cells ± Neuron endrites ² a nerve cell signal direction dendrites cell body ± Structure fits function ² many entry points for signal axon ² one path out ² transmits signal signal direction synaptic terminal dendrite cell body axon synapse myelin sheath
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Fun facts about neurons ± Most specialized cell in animals ± Longest cell ² blue whale neuron ± 10-30 meters ² giraffe axon ± 5 meters ² human neuron ± 1-2 meters Nervous system allows for 1 millisecond response time
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Transmission of a signal hink dominoes! ± Think dominoes! ² start the signal ± knock down line of dominoes by tipping 1 st one trigger the signal ² propagate the signal o dominoes move down the line? ± do dominoes move down the line? no, just a wave through them! ² re-set the system ± before you can do it again, have to set up dominoes again reset the axon
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ransmission of a nerve signal Transmission of a nerve signal ± Neuron has similar system ² protein channels are set up ² once first one is opened, the rest open in ccession succession ± all or nothing response “wave” action travels along neuron ² a wave action travels along neuron ² have to re-set channels so neuron can react gain again
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ells: surrounded by charged ions Cells: surrounded by charged ions ± Cells live in a sea of charged ions ² anions (negative) ± more concentrated within the cell l - charged amino acids (aa - ± Cl , charged amino acids (aa ) ² cations (positive) ore concentrated in the xtracellular fluid ± more concentrated in the extracellular fluid ± Na + + channel Na + Na + Na + Na + Na + Na + Na + Na + Na + K + Na + Na + + l - l - l - - a - K leaks K + + Cl - K Cl Cl Cl K + aa - K + Cl - Cl - aa - aa aa aa - aa - K +
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ells have voltage! Cells have voltage! ± Opposite charges on opposite sides of cell membrane ² membrane is polarized ± negative inside; positive outside ± charge gradient ± stored energy (like a battery) ++++++++ +++++++ – – – – – – – – – – – –
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easuring cell voltage Measuring cell voltage unstimulated neuron = resting potential of -70mV
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ow does a nerve impulse travel? How does a nerve impulse travel? ± Stimulus : nerve is stimulated ² reaches threshold potential ± open Na + channels in cell membrane ± a + ns diffuse to ell Na ions diffuse into cell ² charges reverse at that point on neuron ± positive inside; negative outside ± cell becomes depolarized +++++++ The 1st domino goes own + ––––––– Na + down! +
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ow does a nerve impulse travel? How does a nerve impulse travel?
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Nervous_System_pdf - Nervous System Wh Why do animals need...

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