It is widely known in popular culture that neurons are cells that act as a sort of messenger, sending information from here to there throughout our nervous system.
How neurons, which are the basic functional unit of our brains, work, Spinal cord and nerves, is the topic of today’s article. Find out how these sophisticated engineering works of nature work.
How do neurons work? An overview
Neurons are cells that are part of the nervous system, being its basic functional unit. The main function of these cells is to receive and transmit information in the form of electrical impulses along a complex network or network of neurons, which makes up the nervous system, both the central (CNS), made up of the spinal cord and the brain, and the peripheral (SNP) made up of nerves.
It is clear that, based on this definition, the nervous system could not function without neurons, with glial cells. However, to better understand their functioning, it is necessary to take a series of notes concerning their typology, their structure and their form, because these directly influence their functioning.
The functions of neurons cannot be understood without understanding how these nerve cells are organized. These are the parts of the neuron.
The soma is the cell body of the neuron, and this is where the nucleus is located., In addition to having a strong protein synthesis activity, essential for the functioning of the neuron. It is from there that several protuberances or appendages extend: the dendrites and the axon.
Dendrites are tree-shaped protrusions with thorns that allow the neuron to receive and process information. Depending on the type of signals it receives, it can induce excitation or inhibition of the neuron., To cause or not to give the action potential, that is to say to trigger a nerve impulse.
3. The axon
The axon consists of a single extension in the neuron with a homogeneous thickness. This structure has its origin in the cell body, especially in the axon cone. In motor neurons and interneurons, it is in this axon cone that the action potential occurs.
Axons are covered with a special insulating substance: myelin. This myelin has a key function in the nervous system because it makes nerve impulses more efficient and faster.
Arriving at the end of the axon are many branches, which form bulbous structures called axonal or nerve endings. These terminals form connections with target cells, whether they are motor or interneurons.
Types of neurons according to their function
According to their functions, we can distinguish three types: sensory, motor and interneurons.
1. Sensory neurons
Sensory neurons they are responsible for capturing information outside the body or sensations, Such as pain, light, sound, touch, taste … This information is captured and sent in the form of an electrical impulse, directing it to the central nervous system, where it will be processed.
2. Motor neurons
Motor neurons they receive information from other neurons, responsible for transmitting commands to muscles, organs and glands. In this way, a movement can be performed or a certain biological function can be performed, such as the production of hormones.
Internal neurons are a special type of cell found in the central nervous system that they are responsible for connecting one neuron to anotherIn other words, they function as a kind of bridge. They receive information from certain neurons, whether sensory or other interneurons, and transmit it to others, and can be motor neurons or other interneurons.
Neurons work to form networks
No matter how healthy a neuron is, if it is isolated from others, it is useless. In order for these cells to perform their functions, they must connect with each other, working together.. Thus, by connecting to each other, these cells are stimulated or inhibited, process incoming information and contribute to the emission of a motor or hormonal response. These neural circuits can become very complex although there are also some that are quite simple, especially related to reflexes.
When working as a team, neurons can perform three basic functions: receiving nerve signals or information from other neurons; integrate these signals, in order to determine whether the information is important or not; and communicate signals to target cells, which can be muscles, glands or other neurons.
To better understand these three functions, we will describe an example, a situation in which the three types of neurons are involved according to their function: sensory neurons, motor neurons and interneurons.
Imagine we are making tea, with the teapot on fire. When we see, we activate sensory neurons, especially those responsible for vision, transmitting nerve information captured in the cones and rods of the retina to the brain. Visual information will be processed in the brain and we will be aware that we are seeing the teapot.
As we want to serve ourselves tea, we get ready to grab the teapot. In order to be able to move the arm, we have to use our motor neurons. These neurons received the signal from the brain to activate the muscles in the arms, stretch and grab the teapot. So, we make this movement: we stretch out our arm and grab the teapot, the handle is made of metal.
Turns out we didn’t put out the fire and the teapot was very hot. This sensation is captured by the thermal sensors in the skin when touching the hot handle. This information, picked up by sensory neurons, travels quickly to the spinal cord which, by means of an interneuron, sends information to motor neurons without having to send it to the brain. He is ordered to move his arm quickly to avoid getting burned. However, some information reaches the brain, which interprets it as pain.
Neuron-to-neuron connections are typically formed on the axon and dendrite of two neurons. The meeting place between these two neurons is what is called a synapse or synaptic space, causing the transmission of information from the first neuron (presynaptic) to the next, being the target neuron (postsynaptic).
The transmission of information takes place through chemical messengers, neurotransmitters, Have many types (for example, serotonin, dopamine, acetylcholine, GABA, endorphins …).
When an action potential crosses the axon of the presynaptic cell and reaches its terminal, this neuron releases a neurotransmitter into the synaptic space that binds to receptors on the postsynaptic cell membrane and, thus, nerve signal transmission occurs. product. This signal can be excitatory or inhibitory and, depending on the type of neurotransmitter, one function or another will be exerted, in addition to depending on the path taken by the nerve impulse, in the direction of the corresponding nerve center or the target cell.
And what about glial cells?
While the protagonists are the neurons, you can’t forget your secondary friends, the glial cells, Although that of “secondary” is not synonymous with “consumable”. If the neuron is the basic functional unit of the nervous system, the glial cells are the majority cell. This is why we cannot forget them when trying to explain how neurons work, especially since they play a very important role in supporting the nervous system.
Broadly speaking, there are four types of glial cells, three of which are astrocytes, oligodendrocytes and microglia which can only be localized in the central nervous system. The fourth type is that of Schwann cells, which are found only in the peripheral nervous system.
Astrocytes are the most common type of glial cell in the brain. Its main functions are to regulate blood flow in the brain, maintaining the composition of the fluid surrounding neurons and regulating communication between neurons in the synaptic space.
During the embryonic development of astrocytes, they help neurons reach their destination, in addition to helping to form the blood-brain barrier, the part that isolates the brain from toxic substances that can be dissolved in the blood.
Microglia are linked to macrophages in the immune system, “Scavengers” that eliminate dead cells and waste that can be toxic if they accumulate.
3. Oligodendrocytes and Schwann cells
Oligodendrocytes and Schwann cells share a similar function, although the former are found in the central nervous system and the latter in the peripheral. Both are glial cells that produce myelin, the insulating substance that comes in the form of a sheath around neural axons.
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