Nervous System Communication

Overview

• Neurons communicate through structures called synapses.
• Synapses connect the terminal of a presynaptic cell with the postsynaptic neuron.
• Two types of synapses exist: electrical and chemical.

Electrical Synapses

• Direct connection between two neurons.
• Formed by cell membrane proteins called connexons which create gap junctions.
• Gap junctions:
  • Allow ions to flow between neurons directly.
  • Result in almost immediate response in the postsynaptic cell, with minimal delay.
  • Enable bidirectional signal flow due to open ion diffusion.
  • Allow passage of small molecules like ATP and second messengers, important for cellular mechanisms.

Chemical Synapses

• No physical connection between neurons.
• Existence of a synaptic cleft between presynaptic terminal and postsynaptic membrane.
• Neurotransmitters are stored in the presynaptic cell and interact with receptors on the postsynaptic cell.
• Process:
  • Depolarization of an action potential leads to release of neurotransmitters.
  • Neurotransmitters act on specialized receptors in the postsynaptic membrane.
• Characteristics:
  • Slower than electrical synapses.
  • Allow unidirectional signaling.

Types of Synaptic Transmission

• Axodendritic Synapses: Presynaptic terminal synapses on dendrites of the postsynaptic cell.
• Axosomatic Synapses: Between the terminal and the cell body of the postsynaptic cell.
• Axoaxonic Synapses: Between the terminal and the axon of the postsynaptic cell.

Future Focus

• Discussion on cellular mechanisms via signaling molecules like ATP and second messengers will be covered in later chapters.