HUBS

• Nervous system


  Basic structure
• Central nervous system (CNS)


  • Consists of the brain and spinal cord
  • Composed of 2 general cell classes: neurons and glial
• Peripheral nervous system (PNS) [including ENS]


  • Consists of peripheral nerves and ganglia
  • Composed of 2 general cell classes: neurons and glia
• Neurons (nerve cells)


  • Specialized for transmission of information
  • 4 morphological types
• Glia


  • 3 general features
  • Support neurons
  • 5 basic types (4 in CNS, 1 in PNS)
  • Each type has a specific function
• Neuron


  • Dendrites receive input and send info to cell body
  • Cell body contains nucleus and sums input
  • Axon hillock is where inputs are summated before action potential
  • Axon carries electrical impulses and may or may not be myelinated
  • Axon terminal is the end of the axon and the neurotransmitter release
• Neuron structure


  Functionally related to directional flow of information
• Morphological types of neurons


  • Multipolar
  • Bipolar
  • Unipolar
  • Anaxonic
• Multipolar neurons


  • Multiple processes emulate from the cell body
• Bipolar neurons


  • Two processes emulate from the cell body
• Unipolar neurons


  • One process emanates from the cell body and then branches into dendrite and axon
• Anaxonic neurons


  • No distinct axon and all processes look alike
• Five main types of glial cells


  • Astrocytes
  • Microglia
  • Ependymal cells
  • Oligodendrocytes
  • Schwann cells
• Astrocytes


  • Supply nutrients to neurons
  • Ensheath blood capillaries
  • Injury response
• Microglia


  • Immune cells in the CNS
  • Engulf microorganisms and debris
• Ependymal cells


  • Line fluid-filled spaces of brain and spinal cord
  • Have cilia (hair like processes) to circulate CSF
• Oligodendrocytes


  • Support nerve fibers
  • Ensheath them with myelin
• Schwann cells


  • Support peripheral nerve fibers
  • Ensheath them with myelin
• Oligodendrocytes (CNS)


  Similar to Schwann cells (PNS)
• Myelin sheath


  A lipid (fat) wrapped around an axon
• Myelin sheath


  • Comes from oligodendrocytes in the CNS
  • Comes from schwann cells in the PNS
• Myelin sheath


  • Increases conduction velocity
• Information needs to change form when it moves from one thing to the next

  1. Electrical

  2. Chemical

  3. Electrical
• Electrical


  Releases neurotransmitters (chemical signal) from axon terminal
• Electrical


  • Contains synaptic vesicles (little packs of neurotransmitter)
• Presynaptic neuron


  BEFORE the synapse
• Chemical


  Synaptic cleft
• Electrical


  Contains receptors for neurotransmitter
• Postsynaptic neuron


  After the synapse
• Direction of information flow within (into and out of) the nervous system


  1. Information that goes into the brain - afferent - also called ascending

  2. Response that comes out of the brain - efferent - also called descending
• Eg:


  • Sense something in the environment (afferent)
  • Respond to it with appropriate action (efferent)
• Synapse


  A junction between neurons where communication occurs