A2 Biology Chapter 2

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  • Created by: Chloesn
  • Created on: 16-09-14 20:11
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  • Chapter 2 Nerves
    • Central nervous system
      • Nerves
        • Neurones
          • Action potentials
        • Peripheral nervous system
      • Brain and spinal cord
    • Myelin
      • Schwann cells
        • Wrapped around axon
        • Myelin sheath
          • 1/3 of motor and sensory
          • Increases speed of conduction
        • Uncovered gaps
          • Nodes of Ranvier
            • 1-3mm
    • A reflex arc
      • Pathway which impulses are carried
        • receptor to effector
          • No conscious thought
      • Impulse arrives along sensory neurone
        • Through dorsal root ganglion
          • Into spinal cord
            • Directly to motor neurone
              • Impulse sweeps along axon
                • Arrives at effector
                  • Response can be rapid
                    • Reflex action
                      • Avoid danger
            • Or intermediate neurone then
              • Directly to motor neurone
                • Impulse sweeps along axon
                  • Arrives at effector
                    • Response can be rapid
                      • Reflex action
                        • Avoid danger
    • Structure of a nerve
      • Axons almost always in bundles
        • Protective covering - perineurmium
      • Sensory nerves
      • Motor nerves
      • Mixed nerves
    • Transmission
      • Electrical signals
        • Rapid
      • Brief changes in electrical charge distibution
        • Across plasma membrane
    • Synapses
    • Eels
    • Neurones
      • Motor neurone
        • Action potentials from CNS to effector
          • Muscle or gland
        • Cell body lies in spinal cord or brain
          • Dark specks - ribosomes
          • Impulse towards cell body
            • Cytoplasmic processes extend - dendrites
          • Impulses away from cell body
            • Longer one - axon
      • Transmitter
      • Sensory nerounes
        • Impules via dendrons
          • From sense organs
      • Intermediate neurones
        • Or relay
        • Cytoplasmic processes inside brain/spinal cord
        • Impulses from and to other neurones

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