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Neurons Neurons Presentation Transcript

  • Neurons FOS 3 Infectious Disease Unit
  • Neurons
    • Your body uses chemical signals to send messages from one part to another
    • But if it only used chemical signals it would be way too slow
    • A quicker way is electrical signals!
  • Structure of a Neuron
    • Dendrites- the “antennae” of the neuron, receive information from other cells
    • Axon- a long extension of the cytoplasm that conducts nerve impulses.
    • Axon Terminal- end of axon. Nerve impulse leaves from axon terminal
    • Cell Body- main part of cell
  • Structure of a Neuron
    • Myelin Sheath
      • Fatty outer layer around the axon
      • Causes nerve impulses to move faster
      • Not all neurons have it
  • Neuron Function
    • Neurons have an electrical charge that is different from the charge of the fluid that surrounds them.
      • This difference is called the MEMBRANE POTENTIAL
      • This depends on the concentration of ions inside and outside of the neuron cell
      • Membrane potential is measured in units called Volts
  • Membrane Potential
    • Ions diffuse across a neuron’s cell membrane through special proteins called voltage-gated ion channels .
    • The channels are for specific ions
    • The channels are voltage-gated because they are open or closed depending on the membrane potential.
  • Resting Potential
    • When a neuron is not conducting a nerve impulse it is said to be at rest.
    • The membrane potential of the neuron at rest is called the resting potential.
    • Average is -70mV (inside cell is negatively charged compared to outside the cell)
    • At rest- Na+ channels are closed and K+ channels are open
  • Action Potential
    • A Nerve impulse.
    • A stimulus triggers a change, the Na+ channels open, Na+ ions then move into the axon.
    • Membrane potential increases to about +40 mV as the inside of the axon becomes positively charged.
    • This sudden change causes a chain reaction down the axon.
    • The action potential conducts rapidly down the axon toward axon terminals.
    • Na+ Channels close immediately after the action potential has passed.
  • Action Potential
    • http://www.youtube.com/watch?v=SCasruJT-DU
  • Neurotransmitters
    • When a nerve impulse arrives at axon terminals, it can be transmitted to other cells.
    • The junction at which a neuron meets another cell is called a synapse .
    • The cells do not touch one another at the synapse.
    • The signal must cross from one cell to another through neurotransmitters
  • Neurotransmitters
    • In the transmission across the synapse electrical energy is converted to chemical energy and then back to electrical energy in the 2nd neuron.
    • The chemicals used to cross the gap are called neurotransmitters.
      • Some examples are: acetylcholine (in muscles) and glutamate (in the brain)
  • Neurotransmitters
    • A neurotransmitter is released by exocytosis from the 1st neuron.
    • It diffuses across the gap and interacts with the channels in the 2nd neuron
    • It can either excite or inhibit the 2nd neuron.
    • It can open or close chemical-gated ion channels, this will change the membrane potential.