Synaptic Plasticity

Nervous System Functioning

Key Concepts

  • The nervous system consists of two major subdivisions:
    • Central Nervous System (CNS)
    • Peripheral Nervous System (PNS)
Roles of CNS and PNS
  • Both subdivisions respond to, process, and coordinate sensory stimuli for conscious and unconscious responses.
    • Includes reflex actions (spinal reflexes).
Neurotransmitters vs. Neuromodulators
  • Neurotransmitters (e.g. Glutamate, GABA):
    • Transmit neural information across synapses.
    • Can have excitatory (Glutamate) or inhibitory (GABA) effects.
  • Neuromodulators (e.g. Dopamine, Serotonin):
    • Influence brain activity across multiple synapses, affecting mood, motivation, and learning.
Synaptic Plasticity
  • Synaptic plasticity is critical for learning, involving changes in synapse connections:
    • Long-term potentiation (LTP)
    • Strengthening of synaptic connections due to repeated stimulation.
    • Long-term depression (LTD)
    • Weakening of synaptic connections due to low or lack of stimulation.

Transmission of Neural Information

  • Transmission occurs chemically across synapses via neurochemicals released by presynaptic neurons into the synaptic gap.
  • Neurochemicals bind to specific receptor sites on the postsynaptic neuron dendrites, initiating the next action potential if conditions are met.
Key Structures in Neural Synapse
  • Components:
    • Synaptic gap
    • Axon terminals of presynaptic neuron
    • Dendrites of postsynaptic neuron
Specific Binding of Neurochemicals
  • Not all neurochemicals can bind indiscriminately; they must match receptor site structures.
Neurotransmitters Action
  • Excitatory neurotransmitters increase the likelihood of firing an action potential, while inhibitory neurotransmitters decrease it.

Memory Formation Mechanisms

Process of Glutamate in Synaptic Transmission:
  1. Glutamate is released from presynaptic neuron terminals into the synaptic gap.
  2. It binds to specific receptors on the dendrites of the postsynaptic neuron.
  3. This binding can lead to an excitatory effect, making it more likely for the postsynaptic neuron to fire an action potential.

Neural Connections and Plasticity

  • Neurons are adaptable:
    • Change size, shape, and connections.
    • Neural plasticity allows for the brain's adaptation through experience (learning).
    • Structural changes in synaptic connections are called** synaptic plasticity**.
Types of Plasticity
Sprouting
  • Creation of new neuronal extensions to form new connections.
Rerouting
  • Making alternate connections to create new pathways.
Pruning
  • Elimination of weak or unused connections to strengthen existing ones.

Long-term Potentiation (LTP) and Long-term Depression (LTD)

Long-term Potentiation (LTP)
  • Long-lasting strengthening of synaptic connections that enhances signal transmission.
  • Involves increased neurotransmitter release and receptor site sensitivity.
  • Supports learning/memory retention; "neurons that fire together, wire together."
Long-term Depression (LTD)
  • Long-lasting weakening of synaptic transmission due to lack of stimulation.
  • Helps prune irrelevant synaptic connections, allowing the brain to clear unnecessary pathways.

Summary of LTP vs. LTD

  • Similarities:
    • Both are activity-dependent and play significant roles in learning and memory.
    • Occur at glutamate synapses.
  • Differences:
    • LTP strengthens synaptic connections, while LTD weakens them.

Conclusion

  • Understanding these processes is crucial for grasping how memories form, how learning occurs, and how the brain adapts over time.
Important Terminology
  • Neurotransmitter: A chemical used to transmit a signal across a synapse.
  • Neuromodulator: A substance that modulates the activity of neurotransmitters.
  • Synaptic Plasticity: Changes in synaptic strength due to activity.
Core Concepts to Remember
  • Learning alters synaptic connections via LTP and LTD, which enables the brain to store and retrieve memory efficiently, underscoring the foundational knowledge in psychology related to the nervous system functioning.