Neurons

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Neurons Glial Cells
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• 1. Glial cells
• i. Non-neuronal
• ii. Provides support of functions
• 1. Transports nutrients crossing the
• Blood-Brain Barrier (BBB) - formed
• by special capillary endothelial cells
• 2. Structural support
• 3. Metabolism of some neurotransmitters
• 4. Healing process digestion or
  breakdown of damaged tissue
• 5. Formation of myelin (see slide)

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• iii. Two types of glial cells
• 1. Macroglial Majority of cells, perform
  most functions stated already
• 2. Microglial Inactive unless injury or
  infection in CNS. When damaged
  they
• - increase in size
• - migrate toward injured areas
• - break down tissue of affected areas

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• 2. Neurons (neuronal cells)
• i. Types of neurons
• 1. Unipolar cell body, one appendage
• 2. Bipolar cell body, two appendages
• 3. Multipolar cell body, one large
  appendage (often axon), many other
  smaller appendages (classic example of the
  neuron)
• 4. Multipolar Interneuron Very, very
  small body with a small axon or none at all

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• ii. Structure of neurons
• 1. Cell body - contains nucleus
• 2. Nucleus contains DNA
• 3. Dendrites cell body
• (receives information)
• 4. Receptors receive information using
  a
• chemical signal.
• 5. Axons sends information
• 6. Axon hillock junction between cell
• body and axon
• Lowest threshold for action potential

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• 7. Terminal (buttons or boutons)
  swelling on the surface (see slide)
• - Inside buttons are synaptic vesicles,
• packaging of neurotransmitter
• 8. Myelin sheath insulation for axons
• - comprised of glial cells (see slide)
• A. In CNS its Oligodendrocytes
• B. In PNS its Schwann cells
• 9. Nodes of Ranvier spaces between
  myelinating cells along the axon

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• 11. Cell membranes cover all cells
• - Two layers of fat molecules
• - Tucked inside are channels made up of
  protein molecules (see slide)
• - Protein molecules
• a. Serve as receptors for NTs next
  slide
• b. Serve as channels for ions (Ca,
  Na, K, and Cl-) - next slide
• c. Location along neuron differs in
• the type of channel protein
• d. Membranes are dynamic and alive

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• Two Types of Receptors (more again soon)
• 1. Ionotropic Receptors
• fast acting
• ion channel/receptor complex same
• only a few Neurotransmitter activate them
• 2. Metabotropic Receptors
• slower acting
• ion channel and receptor are different
• most Neurotransmitters act
  on them

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Not in book
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Not in book
Not in book
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• Two Types of channels for ions
• 1. Ligand-Gated Channels (activated by a
  Neurotransmitter directly (ionotropic receptor)
• or separately (metabotropic receptor)
• 2. Voltage-Gated Channels (activated by the
  charge of the
• membrane)
• Location cell body for Na
  and K
• axon hillock
  for Nat and K
• terminal for
  Calcium (Ca)

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• 12. Cytoskeletons (Neurofilaments) inside cell
• provide structural support
• - Microfilaments
• - Microtubules Fairly large, play
  important role in transport
• a. Send vesicles to the buttons where
• they are filled with NT. Acts
  like a conveyor belt.

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• 13. Organelles within the cell
• a. Mitochondria Convert glucose into
  energy we can use ATP (energy source for cell)
• b. Endoplasmic Reticulum Synthesis of fat
  molecules and protein molecules

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• 3. Synapse
• - the junction between cells
  (neurons).
• - synaptic cleft - space between cells
• a. synapse is made of 3 parts
• 1. Presynaptic cell sending side of
• synapse
• 2. Postsynaptic receiving side of
  neuron
• 3. Synaptic Cleft
• b. Purpose promote chemical-electrical
  signal
• c. Types of Synapses axodendritic,
  axosomatic axoaxonic, dendrodendritic

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• 4. Chemical Milieu of Cellular Spaces when the
  neuron is at rest
• Intracellular space extra cellular space
  (inside of cell membrane outside of cell
  membrane)
• a. Cl- Chloride (more outside than inside)
• b. Na Sodium (more outside than inside)
• c. A- Anions (more inside than outside)
• d. K Potassium (more inside than outside)

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Forces that maintain the chemical balance i.
Concentration gradient lesser concentration ii.
Electrostatic pressure attraction toward
opposite charges iii. Na K pumps Throws out
sodium and takes in potassium to keep cell
balanced
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• 5. Four states of neuronal electrical charge
  (potentials)
• a. Resting Membrane Potential
• -70 mV (transient state, constantly
  affected
• by forces that increase or decrease
  charge)
• b. Excitatory Post-Synaptic Potential or
  EPSP Charge across the membrane becomes less
  negative
• - depolarization of the neuron (i.e. decrease
• negative charge from 70mV to 65mV)
• - Leads to an action potential

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• c. Inhibitory Postsynaptic Potential or IPSP
• Charge across the membrane becomes more
  negative
• - hyperpolarization of neurons (i.e. increase
  in negative charge from 70mV to 90 mV)
• - Reduces the likelihood of an action
  potential
• d. Action Potential or AP
• Charge across the membrane becomes less
  negative
• - depolarization of neurons (i.e. decrease in
  
• negative charge from 65mV to 55 mV)
• - charge for the AP begins at Axon
  Hillock
• - significant shift in ions

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Study Questions

• Why is the nervous system in a constant battle
  between EPSPs and IPSPs? What would happen if
  this wasnt the case, in either direction?
• What functions do protein molecules serve in the
  neuronal membrane? Give specific examples.