Skip to content

1.1 Introduction and Refresh

Overview of basic concepts

  • Brain, complex system with $10^{11}$ neurons and $10^{14}$ synapses

  • Cellular components

    • Neurons: information in/out
    • Glia: structural and functional support to neurons
    • Others, like blood vessels, immune cells

  • structure of euron

    • CEll membrane
    • Cell body (soma)
    • In Axon
      • Dendrite
      • Node of Ranvier
      • Myelin sheath
      • Synaptic end bulds
      • Axon terminal
      • Oligodenfrocyte
  • Resting Potential: due to $Na+$ and K+ balance
    • 理解：细胞外的Na多，细胞内的K多，可能出于离子数量的原因，通常对于K存在两个力：Electronic gradient and Chemical gradient. Chemical gradient will equal to Electronic gradient under resting balance: CG give K a force point into cell, and EG give K a force point into out. (外正内负，吸引K往细胞外)
    • 通常，resting potential是-70mv。我们称这样内外电压不平衡的状态的细胞为electrically polarized
  • Action Potentials: send electroinc
    • 当电压差达到threshold potential, 就会引起:depolarize
    • 这个过程通常是由于收到外界刺激，比如相邻的电位变化，突触接受到了化学受体
    • 总之，电位差逐渐从内负外正变成内负外正（voltage-gated sodium channels打开），也即是depolarization;然后，又从内负外正逐渐变成内正外负（voltage-gted potassium channels打开）,即是repolarization and hyperpolarization phase
  • Saltatory conduction
    • action potential propagated through its axon
    • Propagated doesn’t decrease or affect the quality of action potential
    • 动作电位本身不会移动，而是引发下一个神经元膜部分的动作电位
    • 由于前一个神经膜处的refactory period ，动作电位只能向前传播
    • jumping information

  • Neuronal communication

    • Synapse: a structure allowing a neuron to pass an electrical or chemical signal to a target cell
      • Electrical
        • between groups of neurons that need to be synchronized

      • Chemical

        • Neurons separated by a cleft

        • slower response but more modifiable

        • Neurontransmitters

          • Monoamines
            • Dopamine
            • Serotonin
            • Can be stimulatory or inhibitory
          • Neuropeptides
            • AVP, GHRH, GnRH
          • Purines
            • Act through purinergic receptors
          • Gas
            • NO, hydrogen sulfite, Carbon monoxide
            • Fast acting, can also modifying proteins
          • Aminoacids
            • MOst common neurotransmitters: Glu and GABA
            • GABA for inhibitory
              • cause inhibitory postsynaptic potential (IPSP)
                • 这是因为开放了Cl- channel—> cause the more negative potential, making it harder to be activated
            • Glumate for excitatoy
              • Glumate recepotros: NMDA-R and AMPA-R, related to ligand-gated ion channels
              • G-protein coupled receptors
              • The receptor will make excitatory postsynaptic potential
                • 开放钠钾通道；会使得细胞电位更加接近resting potential, making it more likely to be activated
            • Summation
              • Multiple EPSP lead to summed depolarisation and action potential firing
              • IPSP can counteract EPSP summation and prevent action potential firing
            • Glycine is generally inhibitory

  • Glia: 50% of the cells in the brain

    • Derived from same progenitors as neurons
    • Multiple types
      • Microglia: immune cells, protect it against injury and disease
      • Macroglia
        • Astrocytes: 星形胶质细胞。
        • Maintain the environment around synapses
        • Modulate neurons communication
      • Oligodendrocytes
        • Produce fatty substance called myelin, become myelin sheath