17Ch48NervousSystem2005a - Chapter 48. Nervous System AP...

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2005-2006 AP Biology Chapter 48. Nervous System
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2005-2006 AP Biology Why do animals need a nervous system? Remember to think about the bunny…
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2005-2006 AP Biology What characteristics do animals need in a nervous system? fast accurate reset quickly Poor bunny!
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2005-2006 AP Biology Nervous system cells dendrites cell body axon synapse Neuron a nerve cell Structure fits function many entry points for signal one path out transmits signal signal direction signal direction dendrite cell body axon
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2005-2006 AP Biology Fun facts about neurons Most specialized cell in animals Longest cell: blue whale neuron 10-30 meters giraffe axon 5 meters human neuron 1-2 meters Nervous system allows for 1 millisecond response time
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2005-2006 AP Biology Transmission of a signal How is a signal transmitted down neuron? Think Dominoes !
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2005-2006 AP Biology Transmission of a signal Dominoes start the signal knock down line of dominoes by tipping 1 st one send message propagate the signal do dominoes move down the line? no, just a wave through them! re-set the system before you can do it again, have to set up dominoes again reset the axon
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2005-2006 AP Biology Transmission of a nerve signal Neuron has similar system channels are set up once 1 st is opened, the rest open in succession all or nothing response an action travels along neuron have to re-set channels so neuron can react again
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AP Biology Cells: surrounded by charged ions Cells live in a sea of charged ions anions (negative ions ) more concentrated within the cell Cl-, charged amino acids cations (positive ions) more concentrated in the extracellular fluid K+, Na+ Na + Na + Na + Na + Na + Na + Na + Na + Na + K + Na + Na + Cl - K + Cl - Cl - Cl - K + aa - K + Cl - Cl - aa - aa - aa - aa - aa - K + K + channel leaks K + +
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2005-2006 AP Biology Cells have voltage! Opposite charges on opposite sides of cell membrane membrane is polarized negative inside; positive outside charge gradient stored energy (like a battery) + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – –
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2005-2006 AP Biology Measuring cell voltage unstimulated neuron = resting potential of -70mV
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2005-2006 AP Biology How does a nerve impulse travel? Stimulus : nerve is stimulated open Na + channels in cell membrane reached threshold potential membrane becomes very permeable to Na + Na + ions diffuse into cell charges reverse at that point on neuron positive inside; negative outside cell becomes depolarized + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Na + The 1st domino is down
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2005-2006 AP Biology How does a nerve impulse travel?
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17Ch48NervousSystem2005a - Chapter 48. Nervous System AP...

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