Synapses: Connections Between Neurons

Introduction to Synapses

• Definition: Synapses are connection points between two neurons.
• Origin of Term: Comes from Greek, meaning to clasp or join.
• Importance: They enable neurons to communicate, forming a functional nervous system.

Structure and Function

• Composition: Comprised of presynaptic and postsynaptic neurons.
• Action Potential: Electrical messages that trigger synaptic activity.
• Conversion: Synapses convert electrical signals into chemical signals and vice versa.

Types of Synapses

• Electrical Synapses:
  • Immediate communication through ion currents over gap junctions.
  • Fast, direct connections, useful for synchronized actions (e.g., heart muscle cells).
  • Lacks precise control, hence less numerous.
• Chemical Synapses:
  • Uses neurotransmitters to relay messages.
  • Allows for more control and modulation of signals.
  • Slower but more commonly used due to precision.

Chemical Synapse Mechanism

• Process:
  • Action potential arrives at presynaptic terminal.
  • Triggers calcium influx, causing vesicles to release neurotransmitters.
  • Neurotransmitters cross synaptic cleft and bind to receptors on the postsynaptic neuron.
  • Can create excitatory or inhibitory effects.
• Neurotransmitters:
  • Over 100 types, each with distinct roles.
  • Examples include dopamine, serotonin, and norepinephrine.

Neurotransmitter Dynamics

• Reuptake and Degradation:
  • Neurotransmitters are reabsorbed or broken down after their role is fulfilled.
• Impact of Drugs:
  • Drugs can alter neurotransmitter dynamics, affecting mood and perception.
  • Example: Cocaine blocks dopamine reuptake, leading to euphoria and later depletion.

Conclusion

• Synapse Health: Proper function involves balanced excitation and inhibition.
• Dysfunction: Drugs can disrupt synapse function, highlighting their crucial role.

Acknowledgments

• Crash Course Contributors:
  • Thanks to Logan Sanders, Dr. Linnea Boyev, and other supporters.
• Production Team:
  • Script by Kathleen Yale, directed by Nicholas Jenkins and Michael Aranda.