Neuronal Pools and Circuits

Overview

• Neuronal pool: A group of neurons dedicated to a particular function
• Neuronal circuits: Describe the structural orientation of the neurons in a neuronal pool
• Focus on four types of neuronal circuits

Types of Neuronal Circuits

1. Diverging Circuit

• Mechanism: One nerve fiber branches into axon collaterals and synapses with several postsynaptic cells
• Process: Each synapse can branch to connect with more cells, increasing the number of cells communicated with
• Example: One motor neuron can stimulate thousands of muscle cells
• Function: Communication with an increasing number of cells

2. Converging Circuit

• Mechanism: Signals from many axons converge into one postsynaptic cell
• Process: Sensory inputs from multiple areas combine to make a unified decision
• Example: Sensory nervous system, such as the medulla oblongata’s control over respiration
• Function: Integrates multiple sensory inputs (e.g., stretch, chemoreceptive, baroreceptive information)

3. Reverberating Circuit

• Mechanism: An axon collateral doubles back to re-stimulate an earlier neuron in the circuit
• Process: Self-perpetuating circuit, keeps the signal going to target organs
• Example: Medulla oblongata’s control over breathing
• Function: Maintains continuous signal until interrupted by external input (stretch, chemoreceptor, baroreceptor)

4. Parallel After-Discharge Circuit

• Mechanism: Combines diverging and converging circuits
• Process: Signal reaches the target cell at different times due to varying numbers of neurons in each pathway
• Example: Visual processing in the eye
  • Blinking without noticing
  • Afterimage effect (e.g., looking at a lamp or the sun)
• Function: Ensures continuous sensory information delivery without interruption

Conclusion

• This video wraps up the series on the nervous system.
• For any questions, contact the instructor.