Synaptic Transmission

Overview

• Synaptic transmission is the process through which neurons communicate with one another.
• Communication occurs at the synapse, a specialized structure where two neurons come close enough to pass chemical signals.

Structure of a Synapse

• Synaptic Cleft:
  • A microscopically small space less than 40 nm wide.
  • Separates the two neurons (a human hair is about 75,000 nm for comparison).
• Neurons Involved:
  • Presynaptic Neuron: Initiates the signal.
  • Postsynaptic Neuron: Receives the signal.

Neuronal Communication Process

1. Neurotransmitters in Presynaptic Neuron:
   • Chemical signals packaged in vesicles.
   • Each vesicle contains thousands of neurotransmitter molecules.
2. Action Potential:
   • Excites the presynaptic neuron.
   • Causes vesicles to fuse with the presynaptic membrane.
   • Releases neurotransmitters into the synaptic cleft.
3. Interaction with Postsynaptic Neuron:
   • Neurotransmitters bind to receptors on the postsynaptic membrane.
   • Causes an action in the postsynaptic cell (increase or decrease the likelihood of firing an action potential).

Clearing Neurotransmitters

• Diffusion: Neurotransmitters drift away from the synaptic cleft.
• Reuptake:
  • Neurotransmitters are taken back into the presynaptic neuron.
  • Recycled and reused for future transmissions.
• Enzymatic Breakdown:
  • Enzymes break down neurotransmitters in the synaptic cleft.
  • Components are sent back to the presynaptic neuron to synthesize new neurotransmitters.

These steps ensure that synaptic transmission is a regulated process essential for neuronal communication.