THE PHYSIOLOGICAL APPROACH

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THE PHYSIOLOGICAL APPROACH

• Lecture 3

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Early history Parallels with technology

• Aristotle

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Early history Parallels with technology

• Aristotle
• Galen

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Early history Parallels with technology

• Aristotle
• Galen
• Descartes

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Early history Parallels with technology

• Aristotle
• Galen
• Descartes
• Mueller

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Early history Parallels with technology

• Aristotle
• Galen
• Descartes
• Mueller

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Neurons Electrical Signals

• Johannes Mueller (1842)
• Doctrine of specific nerve energies perceptions
  depend on nerve energies reaching the brain and
  that the specific quality we experience depends
  on which nerves are stimulated

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The neuron
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The neuron
Flow of information
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Recording electrical signals in neurons
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Recording electrical signals in neurons
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Recording electrical signals in neurons
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Recording electrical signals in neurons
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Recording electrical signals in neurons
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The resting membrane potential
Na
K
Na
Na
OUTSIDE
Na
Na
K
K
Na
INSIDE
K
K
K
K
Na
Na
OUTSIDE
Na
Na
K
Na
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The resting membrane potential
Na
K
Na
Na
OUTSIDE
Na
Na
K
K
Na
INSIDE
K
K
K
K
Na
Na
Na
OUTSIDE
Na
K
Na
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What accounts for activity states?

• Electrostatic force
• Chemical diffusion
• Selectively permeable membranes

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Electrostatic force Chemical diffusion
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Selectively permeable membranes
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The action potential defined

• Action potential brief propagated changes in
  neuronal polarization that travel rapidly along
  the axon
• Depolarization decreased negativity inside the
  neuron
• Threshold a stimulus intensity just adequate to
  trigger an action potential
• All-or-none property changing stimulus intensity
  does not affect action potential size but does
  affect rate of firing

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The action potential
Na
K
Na
Na
OUTSIDE
Na
Na
K
K
Na
INSIDE
K
K
K
K
Resting membrane potential at potassium
equilibrium (-70mV)
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The action potential
K
Na
OUTSIDE
Na
Na
K
K
Na
Na
Na
INSIDE
K
Na
K
Na
K
K
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Sodium flows into the axon Depolarizes to -40 mV,
or threshold Action potential results
- 40
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The action potential
K
K
K
OUTSIDE
K
K
Na
Na
K
Na
Na
INSIDE
K
Na
Na
Na channels inactivate (absolute refractory
period) completely unresponsive to a second
stimulus Potassium flows out of the axon
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The action potential
K
K
K
K
K
OUTSIDE
K
Na
Na
Na
Na
INSIDE
K
Na
Na
Potassium continues to flows out of the axon
(relative refractory period)
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The action potential
Na
K
Na
Na
OUTSIDE
Na
Na
K
K
Na
INSIDE
K
K
K
K
Resting membrane potential back at potassium
equilibrium (-70 mV)
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The synapse
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Chemical electrical events at the synapse
Presynaptic terminal
Postsynaptic spine
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Excitatory inhibitory input affect firing rate
excitatory input
inhibitory input
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Excitatory inhibitory input affect firing rate
excitatory input
inhibitory input
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Excitatory inhibitory input affect firing rate
excitatory input
inhibitory input
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Excitatory inhibitory input affect firing rate
excitatory input
inhibitory input
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Basic Structure of the Brain
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Localization of function in the brain
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Localization of function in the brain Franz
Joseph Gall (1796)
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