16.24: Neural Circuits

Neural circuits and neuronal pools are two of the main structures found in the nervous system. Neural circuits are networks of neurons that work together to carry out a specific task or process. They consist of interconnected neurons and glial cells, which provide structural and metabolic support.

Neuronal pools are collections of nerve cells with similar functions and interact through chemical and electrical signals. These pools include both interneurons (the central neural circuit nodes that enable communication between sensory or motor neurons and the CNS) and projection neurons, which relay information from one part of the brain to another. Neuronal pools can be further classified into ascending pathways (which move information from lower brain regions to higher cortical regions) and descending pathways (which move information from higher cortical regions to lower brain regions).

An example of a neural circuit is the motor cortex, which controls muscle movement. This neural circuit consists of neurons connecting the spine to different parts of the brain and other neuronal pools in the hypothalamus and cerebellum. Similarly, an example of a neuronal pool is the thalamus, which acts as a relay station between different parts of the brain.

Neural circuits and neuronal pools are essential for communication between neurons within the nervous system and for sending signals throughout the body. The combination of these structures can produce complex behaviors in animals or humans by allowing them to remember past experiences and react appropriately in any given situation. In addition, these structures also contribute to learning, as new neural pathways are formed when a person encounters new experiences and information. Ultimately, neural circuits and neuronal pools work together to allow the brain to function normally and carry out daily tasks.

In the central nervous system, billions of interconnected neurons are organized into specialized functional groups called neuronal pools.

Within each pool, neurons are arranged in five distinct patterns of neural circuits.

In a simple series circuit, one presynaptic neuron stimulates another single postsynaptic neuron, which then stimulates another neuron, and so on.

For a diverging circuit, one presynaptic neuron may synapse with several postsynaptic neurons or cells, such as muscle fibers and gland cells, to stimulate them simultaneously.

In a converging circuit, several presynaptic neurons synapse with a single postsynaptic neuron. For example, different sensory stimuli may trigger the same memory.

While in a reverberating circuit, the signal travels in a series and back to the source or previous neuron, creating a feedback loop. Such circuits are involved in short-term memory or maintaining consciousness.

The parallel processing circuit, or parallel after-discharge circuit, permits one presynaptic cell to stimulate a parallelly arranged neurons synapse with a common postsynaptic cell. Such circuits are thought to be involved in complex activities like mathematical calculations.