Introduction
Neurons are networks or circuits that are responsible for the processing of sensory stimuli and various information. A neural circuit is an entity of interconnected neurons in the brain.
These networks of neurons support the relay of information throughout the nervous system in the form of nerve impulses, or action potentials. They send signals back and forth to the neighboring neurons and also support signaling among the different parts of the brain (the spinal cord and nerves in the peripheral nervous system).
What Are the Main Features of the Neural Circuits?
The neural circuits have 3 specific features:
- Their neurons never function in isolation;
- The neurons of the neural circuits are grouped according to their function;
- The synaptic connections define the type of the neuron circuit.
What Is the Function of the Neural Circuits?
Neural circuits are both anatomical and functional entities. The brain relies on the neural circuit to translate information about the world around us, which is received from the sensory stimuli. Furthermore, it provides the brain with an ability to control movements and learn from gained experiences.
In addition, the neural circuits coordinate the movements in every single neuron cell in the brain. In this way, the brain is enabled to perform its vital functions.
What Are Neurons?
Neurons allow the brain to communicate with all the parts of the body. They are the messengers that relay the information gained via sensory stimuli.
With the help of the electrical impulses and chemical signals, neurons transmit information between different areas of the brain as well as between the brain and the rest of the nervous system that controls the body and its functions.
What Are Synapses?
The nerve cells are not usually in direct physical contact. A brain synapse is a gap between the presynaptic neuron and the postsynaptic neuron. When the neurotransmitters are released into the synaptic cleft, they attach themselves onto the neuroreceptors located in the postsynaptic membrane.
What Is the Structure of a Synapse?
A brain synapse is made of the following functional structures:
- The axon of the sending cell membrane;
- The membrane of the receiving cell dendrite;
- Synaptic vesicles;
- A neurotubule;
- A synaptic knob;
- A synaptic cleft (or gap) located between the presynaptic and postsynaptic endings.
What Is the Function of the Synaptic Cleft in Neural Circuits?
The synaptic gap is a crucial anatomical point in the process of transmission of information pertinent to the fine-tuning of our reactions to the surrounding world.
The synaptic cleft breaks down the neurotransmitters and by doing that, it lowers their concentration. This process slows down the transmission of the nerve impulse between the cells and the brain structures.
What Are the Types of Neural Circuits?
The cerebral cortex comprises many areas with embedded interconnected circuits. Different brain circuits are in charge of the coordination and performance of specific functions.
There are 4 major types of neural circuits:
- Diverging neural circuit;
- Converging neural circuit;
- Reverberating neural circuit;
- Parallel after-discharge neural circuit.
Diverging Neural Circuit
This is a neural circuit where one neuron synapses with a number of postsynaptic neural cells. All neurons are able to form different connections to other postsynaptic cells.
Converging Neural Circuit
The converging neural circuit is formed when a multiple-fiber neuron stimulates a single fiber neuron. The somatic motor system, which innervates and controls the skeletal muscles through motor neurons, is an example of this type of neural circuit.
Reverberating Neural Circuit
This is a neural circuit in which the neuron impulses that were initially activated by the stimuli continue to be reactivated. In this way, the retrieval of information is enabled.
Parallel After-discharge Neural Circuit
A neuron projects its fibers to several chains of neurons in this type of neural circuit. Each chain in the circuit is created by a different number of neuron cells. However, their signals converge onto a single fiber neuron.
Which Brain Processes Are Supported by the Neural Circuits?
We can distinguish several main processes that are activated in the neural circuits:
- The process of neural oscillation – This neural process refers to the rhythmic and/or repetitive electrical activity of the neural tissue in the central nervous system. It is triggered by stimuli received via the sensory organs.
- The process of convergence and divergence of information – These two processes are very important aspects of neurotransmission. Namely, by receiving information from multiple neurons, the neuron cells converge, i.e. consolidate the information. On the other hand, by sending chemical or electrical signals to different neuron cells, they relay the information to the neurons of the processing areas of the cerebral cortex.
- The process of summation – There are two types of summation: temporal and spatial. In the temporal summation, multiple action potentials are generated in a short period in order to reach the desired threshold of the postsynaptic neuron. On the other hand, multiple action potentials come to pass at the presynaptic terminal and trigger the release of enough neurotransmitters to exceed the trigger point of the postsynaptic neuron in the spatial summation.
- The process of co-transmission of neurotransmitters – When two or more neurotransmitters are released from a single presynaptic terminal, the process is labeled as co-transmission. Such is the case with dopamine and glutamate – neurotransmitters that are released together.
Fun Facts
Did you know?
- There are approximately 1,000,000,000,000,000 (one quadrillion) neural circuits in the brain.
- The estimated trillions of synapses in the brain enable our every thought and gesture.
- It takes time for the neurons to develop. Namely, the first neurons start to form from a single, thin layer of tissue in an embryonic structure that is labeled as the neural tube.
- The neurons develop their dendrites and axons during the migration from the place in which they were first formed to their final location in the cerebral cortex.
- The formation of synapses between neurons in the brain begins at around two months before birth. This is a process that continues at least through the first year of life.
- The electrical or chemical impulse from one neuron to another can pass via connections between various parts of the neuron cell.
- Our brain is who we are – everything we think and feel.
- The neural circuits are able to regulate their own activity by using a feedback loop.
- Each neuron has the role of a ‘switch’ that controls the flow of information in the brain.
- The sensory path of the central nervous system is an example of a diverging neural circuit.