What is a neuron?

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What is a neuron?
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The Neuron

• A neuron is a nerve cell
• like any other cell in the body
• Neurons are similar to other cells in the body in
  some ways
• However, neurons differ from other cells in the
  body in some ways

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3 major classes of neurons

• Sensory (afferent)
• Motor (Efferent)
• Interneurons
• Glia cells
• development
• housekeeping
• insulation
• protection

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Simple Reflex Pathway
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The process of neural communication

• Within cells - action potential
• Between cells - synaptic transmission
• Components dendrites, soma (cell body), axon,
  and terminal buttons of axon

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The Neuron at Rest

• Resting potential - Cell is Polarized
• neuron membrane separates charged ions, producing
  a voltage potential
• sodium (NA), potassium (K), chloride
• (Cl-), and protein molecules (A-)
• selectively permeable (semi-permeable)
• sodium-potassium pump maintains ionic imbalance
• inside of neuron is negative relative to outside
  (about -70mV)

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Reception of Input

• Graded potentials
• Excitatory potentials -depolarizing current
• Inhibitory potentials - hyperpolarizing current
• determines which ion channels open
• Excitatory input causes the ion channels to allow
  sodium ions into neuron
• allows neuron to fire
• Inhibitory input causes ion channels to keep
  neuron negatively charged
• prevents neuron from firing

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Synaptic Transmission

• Presynaptic and postsynaptic neurons
• Transmission involves movement of
  neurotransmitters across synaptic cleft
• about 200 angstroms (one ten-millionth of a
  millimeter) in width b/t neurons
• Once AP reaches terminal button, vesicles spill
  contents into gap
• Traverse cleft, attach to receptor molecules
• Either increase (E) or decrease (I) neural firing

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Neurotransmitters

• Acetylcholine, ACH
• learning and memory
• motor neurons and muscles
• major excitatory neurotransmitter
• Gamma-Amino Butyric Acid (GABA)
• major inhibitory neurotransmitter
• anxiety

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Neurotransmitters

• Catecholamines
• Norepinephrine
• undersupply - depression
• Dopamine
• oversupply - schizophrenia
• undersupply - Parkinsons
• Serotonin
• mood, sleep, and eating
• Endorphins
• natural pain killers

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Neurotransmitters