Meaning of Neuron

What is Neuron:

Neuron is a cell of the central nervous system that has the ability to receive and decode information in the form of electrical and chemical signals, transmitting them to other cells.

Neurons are the most important cells, since they are responsible for the transmission of electrical impulses through the synapse process, which constitutes the principle of the functioning of the brain.

Neuron comes from the Greek “neûron”, which means nerve.

Neurons were first observed in 1873 by the Italian anatomist Camillo Golgi. He used silver salts to stain the neurons black, managing to visualize their structure and identify different types.

structure of a neuron

Each neuron is made up of four parts or structures:

Neuron

Nucleus

It is a structure located in the center of the neuron in which genetic information is concentrated. In the nucleus there is also a pair of nucleoli, the chromatin, (in which there are proteins and deoxyribonucleic acid DNA), and the accessory body of Cajal. The latter is a kind of sphere in which proteins essential for neuronal activity accumulate.

pericarion

Also called the soma, the perikaryon is the cell body of the neuron. Within it are the ribosomes, which are essential to carry out protein synthesis, and the mitochondria, responsible for supplying energy for cellular activity.

Nissl bodies and the Golgi apparatus are also found in the soma. Nissl bodies are granules in which there are accumulations of rough endoplasmic reticulum, responsible for transporting and synthesizing secretion proteins. The Golgi apparatus is the organelle that is responsible for the addition of carbohydrates to proteins, through a process called glycosylation.

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dendrites

They are multiple ramifications that start from the perikaryon and that act as a zone for receiving stimuli and cellular feeding, in addition to establishing connections between neurons. They are rich in organelles that contribute to the synapse process.

axon

It represents the main extension of the neuron and can measure several tens of centimeters. The axon is responsible for conducting the nerve impulse to the dendrites of other neurons.

Without a coating, the axons could not transmit impulses quickly, as their electrical charge would be lost. By virtue of this, many neurons are covered by a substance called myelin, which is produced by the Schwann cell.

Schwann cells (which are currently called neurolemocytes) cover the axons with their myelin content, leaving certain spaces between them, known as Ranvier nodes. These breaks in the myelin sheath allow the electrical impulse to travel faster.

neuron function

The main function of the neuron is to transmit nerve impulses to other cells. This is translated as “instructions” for the functioning of the organism. For example, the voluntary movement of a muscle, or involuntary but necessary reactions such as the perception of pain from a blow or burn, just to name a few.

This process of receiving, processing and sending messages is carried out during the synapse, a process that can be of two types:

  • electrical synapse: is characterized by the transmission of ions between one neuron and another through protein connections, called junctions gap or gap junctions, which allow the transmission of the electrical impulse without the intervention of a neurotransmitter being necessary. The electrical synapse is bidirectional and faster than a chemical synapse.
  • chemical synapse: In this case, neurons release and receive neurotransmitters, which are small molecules that carry information to an immediate cell. Some of the best known neurotransmitters are dopamine, acetylcholine, serotonin, norepinephrine, endorphin, and oxytocin.
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See also Synapse

types of neurons

Neurons can be classified according to several criteria:

Neurons according to their function

In this case, the neurons can be:

  • motor neuronsThey are responsible for voluntary and involuntary body movements.
  • sensory neurons: They are the ones that are in charge of receiving and processing external information, captured by the senses (smell, taste, touch, hearing, sight).
  • interneuronal neurons: They are organized in large networks, and their function is to generate cognitive processes, such as thoughts and memories.

Neurons according to their shape

There are five types of neurons according to their morphology:

  • pyramidal neuronsThey are shaped like a pyramid.
  • spindle neuronsThey are cylindrical neurons.
  • polyhedral neurons: They have a very defined geometric shape, with multiple faces.
  • stellate neurons: They are characterized by having many extremities, which gives them a shape similar to a star.
  • spherical neuronsThey have a circular or sphere shape.

Neurons according to their polarity

According to the number of their electrical endings, neurons can be classified into:

  • unipolar neurons: They are neurons that have a single extension that behaves like an axon and a dendrite at the same time, like the neurons found in the ganglia of invertebrate animals.
  • monopolar neurons: in this case, the neuron has a dendrite that bifurcates into two branches. The posterior ganglia of the spinal nerves, for example, are monopolar.
  • bipolar neuronsThey are neurons with one axon and one dendrite. The vestibular ganglia, which are located in the ear and are responsible for balance, belong to this group.
  • multipolar neuronsThey are neurons with one axon and multiple dendrites. Most neurons are of this type.
  • anaxonic neurons: dendrites and axons cannot be distinguished due to their small size. The ocular retina has these types of neurons.
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See also Nervous system