Descartes View

1
Descartes View
KW 4-1
2
Luigi Galvani (1737-1798)
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Electrified Frogs

• Luigi Galvani
• Frog legs attached to wire in market
• Electrical storm made legs move
• Early idea of electrical properties of nervous
  system

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Electrical Stimulation
KW 4-2
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Neural Communication
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The journey of nerve message
As message passes along the nerve, Electrode
indicates a shift from negative to positive
and then back to negative again
KW 4-4
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Neural Communication
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Hodgkin and Huxley
Two Cambridge profs and a squid get together
(1939)
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Squid and axon
KW 4-5
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Microelectrodes
KW 4-7
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Recording from an axon
KW 4-6
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Reversal of charges
KW 4-15
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Ions
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Ions on the move
KW 4-8
15
Ions meet a barrier
No pores No movement of ions
With pores, ions can move.
Charge develops
KW 4-9
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Ions of the axon
KW 4-10
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Channels
KW p. 129
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Pumping ions
KW p. 125
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Channels and pumps
KW 4-10
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Resting Cell Recording
KW 4-10
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Resting Cell Charges
KW 4-10
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Depolarization
A Graded Potential
KW 4-11
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Hyperpolarization
KW 4-11
A Graded Potential
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Axons get polarized
KW 4-11
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Na and K work together
KW 4-13
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Phases of the action potential
KW 4-14
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Neural Communication
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Reversal of Charges
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Falling dominos
KW p. 131
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Ion flow
KW 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 doesnt lose power
• Full strength to the end of axon
• Axon can be any length

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Analogies for Action Potentials

• Band of Fire moving down tube
• Ring sliding down a string
• Doing the wave in stadium

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End of segment one