Nerve Impulses

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Nerve Impulses
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How is information transmitted within one
neuron?..and from one neuron to the next?
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• resting state, the neuron is more negative inside
  compared to outside. The resting membrane
  potential is -70 millivolts (mV). The reason for
  this is because of the distribution of charged
  ions

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• Sodium (Na) and potassium (K) are positive
  ions.
• They are found on both sides of the membrane.
• More Na ions on outside
• K ions are more concentrated inside the neuron.
• Unequal pumping (3 Na out to 2K in)

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• Stimulation of neuron results in Na gates open
  allowing Na to rush in
• Depolarization of the membrane in the area where
  the stimulation occurred.
• Depolarization of an area of membrane stimulates
  more Na gates in adjacent areas to open, thus
  spreading the depolarization.

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• Immediately after depolarization, Na channels
  close and K channels open causing K to flow
  out.
• This process returns positive charge to the area
  just outside the membrane, thus restoring the
  resting polarity.

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What happens when the impulse reaches the end of
the axon?

• Synapse point of impulse transmission between
  neurons. The synaptic gap\cleft is a small gap
  separating neurons.

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A synapse

• occurs between the axon of a pre-synaptic neuron
  a dendrite or cell body of a post-synaptic
  neuron.
• neurotransmitters are chemicals released from one
  neuron at the presynaptic nerve terminal.

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• Neurotransmitters cross the synapse where they
  may be accepted by the next neuron at a
  specialized site called a receptor.

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Neurotransmitter Substances

• Acetylcholine (ACh)
• Dopamine (DA)
• Norepinephrine (NE)
• Serotonin (5-HT)
• Histamine
• Epinephrine

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Excitatory and inhibitory postsynaptic potentials

• A synaptic potential can be excitatory or
  inhibitory
• There are more
• than 50
• different
• neurotransmitters.

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The big picture