Understanding Neuronal Communication Basics

Sep 16, 2024

Perceptual Motivation and Emotion Course: Lecture on Communication Between Neurons

Introduction

  • Previous Learning:
    • First week: Main structures and functions of neurons.
    • Last week: Transmission of information within a neuron (resting potential to action potential).
    • Encouragement to review prior materials if concepts are unclear.

Communication Between Neurons

  • Focus of Today's Lecture: Understanding how information is sent between neurons.
  • Key Figure: Santiago Ramon y Cajal - Demonstrated neurons are separate with gaps, termed synapses by Charles Sherrington.

Synaptic Communication

  • Presynaptic vs Postsynaptic:
    • Presynaptic Neuron: Sends information, located before the synapse.
    • Postsynaptic Neuron: Receives information, located after the synapse.
    • Postsynaptic Potential: Changes in electrical potential (depolarization or hyperpolarization).

Sherrington's Findings on Synaptic Transmission

  1. Transmission Speed:
    • Slower in the reflex arc than along an axon, suggesting unique synaptic processes.
    • Reflex arc: ~15 m/s, Axon: ~40 m/s.
  2. Summation in Neuronal Response:
    • Temporal Summation: Multiple weak stimuli over time can trigger a response.
    • Spatial Summation: Multiple weak stimuli at different locations can also trigger a response.
    • Analogy: Poking scenarios to illustrate temporal and spatial summation.
  3. Reciprocal Inhibition:
    • Excitation of one muscle group comes with inhibition of another (e.g., flexor vs. extensor muscles).
    • EPSP (Excitatory Postsynaptic Potential): Increases likelihood of action potential.
    • IPSP (Inhibitory Postsynaptic Potential): Decreases likelihood of action potential.

Detailed Explanation

  • Graph Analysis:
    • Depicts EPSP and IPSP.
    • Graded potentials decay over time and space, unlike action potentials.

Integration in Neurons

  • Summation of Information:
    • Neurons integrate multiple EPSPs and IPSPs over time and space.
    • An action potential occurs only if the combined potentials reach the excitation threshold.

Synaptic Transmission Mechanisms

  • Post-synaptic Potentials:
    • Usually subthreshold, requiring summation (temporal and spatial) to trigger action potentials.
  • Role of Axon Hillock:
    • Integrates EPSPs and IPSPs to determine if threshold is reached.

Conclusion

  • Importance of understanding synaptic processes and summation for neuronal communication.
  • Encouragement to review textbook diagrams and explanations for clarity.