Chapter 10

Synaptic Plasticity

• Synapses change strength based on neurotransmitter interactions.

• Glutamatergic Synapse:

  • Glutamate binds to receptors at the presynaptic axon terminal.

  • Opens Na+ or Ca2+ channels, prolonging depolarization.

  • This process strengthens the synapse.

• Retrograde Signaling:

  • Postsynaptic cells can send signals back to presynaptic terminals.

  • Endocannabinoids:

    • Released from postsynaptic dendrites.

    • Bind to presynaptic cannabinoid G-protein-coupled receptors.

    • Prolong depolarization and influence gene expression.

Long-Term Effects on Synaptic Strength

• Gene transcription is influenced by neurotransmitter levels.

• Reuptake Transporters:

  • Greater numbers result in faster neurotransmitter removal, weaker synapse.

  • Fewer transporters lead to longer neurotransmitter presence, stronger synapse.

• Postsynaptic mechanisms can increase or decrease neurotransmitter receptors:

  • More receptors lead to stronger synaptic response.

  • Fewer receptors lead to weaker synaptic response.

Neuroplasticity Mechanisms

• G-Protein-Coupled Receptor Effects:

  • Influence the branching of axons/dendrites and sprouting of dendritic spines.

  • Facilitate formation of new synapses.

• Neurogenesis:

  • New neuron formation from precursor cells occurs in adults, notably in the hippocampus.

  • Estimated addition of 1400 new neurons daily in the human hippocampus.

  • Hippocampus Role:

    • Important for memory formation and stabilization.

    • Named for its seahorse shape.

Neuroplastic Changes Across the Lifespan

• Most robust during early life, susceptible to wiring changes.

• Critical Life Stages:

  • Infancy, childhood, adolescence, and early adulthood are pivotal for brain development.

  • Neurogenesis, axonal growth, synapse formation, and myelination are ongoing.

  • Myelination in cortical neurons continues past age twenty, enhancing communication.

• Significance of Early Experiences:

  • Good parenting and emotional environments are vital.

  • Societal impacts of prioritizing early learning experiences, especially in education.

• Investment in childhood experiences yields great benefits for individuals and society.