Nervous System: Synaptic Transmission Notes

Fundamentals of the Nervous System: Synaptic Transmission

Transmission of Information

  • Information transmission occurs:
    • Within each neuron (covered in the last lecture).
    • Between neurons (focus of this lecture).

Lecture Outline

  1. Types of Synapses: Electrical and Chemical.
  2. Synapses Transmit Information from One Neuron to Another.
  3. Principles of Synaptic Integration.
  4. Studying the structure and function of neural networks.

Introduction to Synapses

  • Synapses
    • Coined in 1897 by Charles Sherrington.
  • Electrical Synapses
    • Proven in 1959 by E. Furshpan and D. Potter in crayfish.
    • Information flows within and between neurons via electrical signals.
  • Chemical Synapses
    • Solid evidence provided in 1921 by Otto Loewi.
    • Information passes between neurons through chemical signals.
  • Sparks and Soups
    • Two groups of scientists with opposing views regarding the nature of synaptic transmission.
      • Electrical synapses were thought to transmit information via electrical signals (Sparks).
      • Chemical synapses transmit information through chemical signals (Soups).
  • Synaptic Transmission Hypotheses:
    • The physical nature of synaptic transmission was debated for a century.

Electrical Signals as the Language of the Nervous System

  • Otto Loewi (1873-1961)
    • German-born pharmacologist.
    • Discovered acetylcholine (ACh).
    • Nobel Prize laureate in Physiology or Medicine in 1936.
Loewi's Experiment
  1. Experiment Setup: Loewi electrically stimulated the vagus nerve of a frog heart, causing it to slow down.
  2. Observation: The fluid surrounding the slowed heart was collected and applied to a second heart.
  3. Result: The second heart also slowed down, indicating that a chemical substance, not electrical signals, was responsible for the effect.
  4. Conclusion: The release of acetylcholine (ACh) acted on inhibitory muscarinic receptors in the heart muscle to slow down its contraction force and frequency.
    • If electrical signals were responsible for slowing down the heart, there would be nothing in the liquid to affect the second heart.

Historical Milestones in Synaptic Transmission Research

  • 1897: Charles Sherrington introduces the term