Fifth Lecture

Synapses

Synapse type
  • Ionotropic effect: ion channels
  • Metabotropic effect: G protien releases, and activates second messenger systems (slower, can open many channels, but longer lasting)

    • Neurotransmitters

    Types
  • Biogenic amines (dopamine)
  • Amino acids (glu, gaba)
  • Peptides (endorphins, etc)
  • Other (NO, adenosine)

    • Drugs

    The discovery of neurotransmitters is closely linked to drugs. The drugs act on specific receptor or neurotransmitter to work. But usually have more than one effect.
    Chemical structures
    Very specific - even the slightest difference can cause drastic changes.
    Can
  • Disrupt presynaptic vesicles
  • Displace neurotransmitters
  • Block neurotransmitter release
  • Inhibit synthesis of NT
  • Block reuptake of NT
  • Block degrading enzyme
  • Mimic neurotransmitters
  • Block postsynaptic site
    • In number
    • Synaptogenisis or synaptic widhtdrawel
    • THe efficacy of existing asynapsis is changed by changing the amount of neurotransmitter released
    Hebbs Law
    Correlated signals get strengthened synapses
    What happens after NT are released into the synaptic cleft?
  • Enzymatic degradation of the NT
  • Diffusion out of the cell
  • Re-uptake into the synaptic button
    • Examples
    Aceta(something something) - ACH: responsible for muscles!
    Where do they come from?
    Synthesized from precursor molecules that are derived from the food we eat.
    Evolutionary time
    More important systems evolved more synaptic connections

    How and why do synapses change?

    Real time
    Learning and memory
    Developmental time
    Refinement of connections based on use
    Example: Serotonin
    Dosages
    Clinical trials determine effective dose. Trial and error.
    Absorption
  • Can pass thru blood brain barrier
  • Block Na+ channel in medicine (anesthesia)
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