Neurons: Signaling Elements of the Brain

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Neurons Signaling Elements of the Brain
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Neurons (Nerve Cells)

• gt100 billion
• All thinking , feeling, movement produced by
  neurons communicating with each other

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Many different morphologies
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Learning Capabilities
20,000

• Depend on quantity of neurons the complexity in
  which they are interconnected, NOT on the
  different types
• The greater the of neurons the more complex
  the patterns of interconnections, the greater an
  animals capability for different types of
  learning.

300,000
10 billion
100 billion
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Neurons Have Four Components
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Information Flow
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Never act alone, organized into circuits
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NEURONS ARE NOT TOUCHING!

• They are separated by a gap called the SYNAPTIC
  CLEFT (2 X10-8 M)

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Nerve Signals are Stereotyped

• Same language conveys info about odors, sound etc
  commands.
• Pathways patterns of signals determines how
  the brain interprets the nature of information

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How Neurons Talk to Each Other
Presynaptic neuron
chemical
Electrical signal
Postsynaptic neuron
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Key Terms

• Ion - a charged chemical element
• Electric currents - (w/in living organisms) -
  carried by movements of ions across membrane of
  cells
• Potential - a force created when ions of opposite
  charge are separated

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Resting Potential Generation

• Na/K Pump active
• Na channels closed
• K channels open

RP - produced by unequal distribution of ions
between inside outside of neuron
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Action Potential

• Stereotyped depolarization
• Propagates along axon
• Voltage-gated ion channels
• All-or-none

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How is AP triggered?
Synaptic inputs ? Postsynaptic Potentials
Threshold
Sum ? Threshold ? Action Potential
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Synaptic Transmission
Ion flow ? EPSP or IPSP
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Exocytosis
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Neurotransmitters carry the message BETWEEN
neurons

• Common Neurotransmitters
• Glutamate
• GABA
• Acetylcholine
• Norepinepherine
• Epinephrine
• Serotonin
• dopamine

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