Presentation adapted from text materials from Vanders Human Physiology, 11th edition, Widmaier, Raff

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• Presentation adapted from text materials from
  Vanders Human Physiology, 11th edition,
  Widmaier, Raff, and Strang

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Nervous system

• Al Mina, M.D.
• Erskine College

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Structures of Nervous System

• Central Nervous System (CNS)
• Brain
• Spinal cord
• Peripheral Nervous System (PNS)
• Nerves that connect CNS with effectors (muscles,
  glands, sensory structures)

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Types of Neurons
Cell body (soma) Axon Dendrites Axon Terminals
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Neuron Structures
Axon hillock (Initiating zone) Collaterals
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A Neuron
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Axon sheath

• Composed of myelin modified plasma membrane
• Formed by oligodendrocytes in CNS, Schwann cells
  in PNS
• Increases conduction speed
• Has small gaps (nodes of Ranvier)

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Myelin Sheath Produced by Oligodendrocyte
Schwann Cell in PNS
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Long axon needs materials

• Over 1 meter to travel
• Axonal transport movement by microtubules
• Kinesins moves from cell body toward terminals
  (anterograde)
• Dyneins move toward body (retrograde) used by
  pathogens

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Classes of neurons

• Afferent move toward CNS (have single process)
• Interneurons connect neurons within CNS
• Efferent move to periphery

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Functional Classes of Neurons
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Connections

• Junction synapse signal transmitted between
  neurons
• May be zero or millions of synapses in chain from
  afferent to efferent neuron, depending on
  complexity
• Signal sender in synapse presynaptic neuron,
  reciever is postsynaptic

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Other cells

• Glial cells all non-neurons in CNS.
• Oligodendrocyte forms myelin
• Astrocyte regulates extracellular fluid,
  stimulates tight junctions between CNS capillary
  walls (blood brain barrier)
• Microglia immune response
• Ependymal cells regulate cerebrospinal fluid
  (CSF)

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Growth and repair

• Undefferentiated cells become neurons or glia,
  migrate to desired location, starts growing axons
  and dendrites
• Growth cone helps axon find path
• Development continues until adulthood

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Repair contd

• Peripheral axons can regrow if cell body
  unaffected
• Growth cone reforms, growth occurs at 1 mm/day
• Crush injuries do not repair well, especially in
  CNS
• ? Stem cells

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Membrane potentials

• Difference in charge across membrane
• All cells have a resting membrane potential
  (inside cell more negatively charged than
  outside)
• Magnitude varies widely from cell to cell based
  on type
• Neurons are between -40 and -90 mV