Synapses: The Powerful Connectors in the Nervous System

Introduction to Synapses

• Definition: Synapse is the meeting point between two neurons.
• Function: Converts the structure of neurons into a functional nervous system through connections.
• Etymology: From Greek meaning "to clasp or join."

Importance of Synapses

• Communication: Neurons need connections to communicate; otherwise, they are non-functional.
• Quantity: Human brain has 100 billion neurons, each with 1,000-10,000 synapses, totaling 100-1,000 trillion synapses.
• Adaptability: Synapses function like tiny computers, capable of adapting and changing strength based on use.
• Role in Experiences: Influence learning, memory, psychiatric disorders, and drug effects.

Types of Synapses

Electrical Synapses

• Speed: Immediate, like a group text.
• Function: Uses ion currents through gap junctions; no signal conversion, allowing synchronized actions.
• Examples: Heart muscle cells need speed and teamwork.

Chemical Synapses

• Control: More precise and selective, slower than electrical ones.
• Neurotransmitters: Use chemical signals to deliver messages across synaptic gaps.
• Signal Conversion: Converts electrical signals to chemical, then back to electrical.
• Components:
  • Presynaptic Neuron: Sends signal through presynaptic terminal.
  • Postsynaptic Neuron: Receives signal, located on dendrite or cell body.
  • Synaptic Cleft: Gap between neurons where neurotransmitters diffuse.

Chemical Synapse Functionality

• Action Potential: Activates voltage-gated calcium channels, releasing neurotransmitters.
• Neurotransmitter Binding: Causes ion channels to open, exciting or inhibiting the neuron.
• Types of Neurotransmitters:
  • Excitatory: Depolarize, making neurons more likely to fire.
  • Inhibitory: Hyperpolarize, making firing less likely.

Neurotransmitter Lifecycle

• Diversity: Over 100 types, affecting various body functions.
• Reuptake and Degradation: Post-function neurotransmitters are reabsorbed or broken down.

Drug Effects on Synapses

• Manipulation: Drugs affect production, release, reuptake, or mimic neurotransmitters.
• Example - Cocaine: Blocks reuptake of serotonin, dopamine, and norepinephrine.
  • Effects: Initial euphoria, followed by depletion of neurotransmitter supply, leading to dysfunction.

Conclusion

• Synapse Functions: Balancing excitation and inhibition, electrical vs. chemical signaling.
• Impact of Drugs: Artificial imbalance illustrates system vulnerabilities.

Acknowledgments

• Supported by individuals and organizations for educational purposes.