Neurons – Its structure, function and types
As a simple definition, we will tell you that the neuron is the cell that is part of our nervous system being its functional unit. Neurons, serve to communicate the messages we perceive from the external world and send them to our brain in the form of impulses through nerve fibers. Stimulus receptors have the function of capturing information from the environment and transmitting it to the central nervous system.
Neuron structure
Well, different types of variable neurons can be presented in shapes and sizes but all consist of three essential parts: dendrites, cell body or soma and axon. Its structure was investigated by Camilo Golgi, Italian doctor and histologist who used impregnation techniques with silver salts to study the neuron, which became creditor of the Nobel Prize in Medicine in 1906.
To understand the structure, it is best to imagine you observe them from a microscope first observing the cell body, which emits extensions, one of them the dendrites who are responsible for transmitting the different stimuli to the cell body or soma. The axon, terminal prolongation of the neuron that conducts the impulses that come from the body of the cell to other neurons through the synapse. This is a physiological valve that relates to the different neurons allowing the passage of nerve impulses in a single direction, of axon of a neuron to the following dendrite.
What function do neurons have?
Incredibly, neurons fulfill the function of transmitting the nerve impulse, which is accompanied by chemical and electrical changes and also require energy. This nervous impulse that is transmitted from one neuron to another through synapse does not pass directly, since there is a small space between the cells. Experiments have shown that in the axon there are chemical substances known as mediators or neurohumores or neurotransmitters. One of them segregated acetylcholine at the synapse level, causes the excitation of the next neuron that triggers the transmission of nerve impulse.
On the other hand, certain neurohumores are synthesized at the level of the cell soma, then they are driven to the axon where they are stored;Subsequently, it exerts its action through the axonic terminal branch where they are released towards the synapse. After the excitation of the neuron in the synapse, the neurotransmitter is eliminated, disintegrated or reabsorbed by the axon to recycle it.
Other neurotransmitters are epinephrine, norepinephrine, norepinenaline serotonin and dopamine;All are intimately related to countless responses such as anxiety and depression states.
Characteristics of neurons
The different types of neurons make a synaptic transmission which is characterized by the following:
- Nervous impulses always make their conduction in one sense: from the axon of one neuron to the body or dendrites of the other neuron.
- Only through chemical intermediaries is that the propagation of the impulse is possible.
- In the central nervous system, there are exciting and inhibitor -type neurons and each of them releases its own neurotransmitter substance, which allows them to classify them more easily.
- Depending on the size of the neuron, the speed can vary from 1 to 100 meters per second.
- The synaptic transmission delay from one neuron to another is 5 milliseconds.
Types of neurons
In fact, the types of neurons in the human body are very diverse but they can be divided between the neurons that conduct nerve impulses from the receptors to the central nervous system better known as sensitive or afferent neurons; Those that carry the impulses from the CNS to the effectors are motor or efferent neurons, and finally the neurons responsible for connecting the sensitive with motories are called association or link neurons found in the brain and spinal cord. Let’s see each one!
Sensitive neurons
When we talk about the different types of neurons, sensitive play a crucial role. These are responsible for carrying the impulses from the different mechanisms of the organism: view, ear, smell, touch and taste to the central nervous system. The end of these is to feel sensations such as pain, heat, flavor, among others.
Motor neurons
Motor or motor neurons allow the journey of nerve impulse to the muscles. For what purpose? To allow you to perform the movements of your muscles in a balanced way. Also, it allows the movement of other body parts such as heartbeat, intestines, lungs.
Link neurons
Interneurons or link neurons are responsible for processing thoughts and connecting these with nerve impulses. They are one of the most complex types of neurons and are found in the central nervous system.
Neurons according to neurotransmitter
As we have said before, neurons are able to reach synapses through neurohumores and the different segregations of these also allow to classify neurons; If it transmits serotonin, it will be known as serotonergic neurons, if they transmit dopamine it will be classified as dopaminergic neurons, if it is the inhibitory neurotransmitter gaba then we would be talking about gabaergic neurons, if the neurotransmitter is glutamate then we would be in the presence of glutamtergic neurons and so on since As you can imagine, there are many.
Neurons according to their morphology
If we classify these cells according to their morphology we can find three types of direct neurons: unipolar neurons, which are characterized by having a single branch that extends from the soma and serves as a dendrite and axon; Bipolar neurons that have two extensions that leave the soma to act one like dendrite and the other as axon; And finally, multipolar that have many dendrites and a single axon and are usually found in the brain.
Neurons according to the type of synapse that triggers
Another classification of the types of neurons is through the type of synapse that is capable of performing. In this case we find inhibitor neurons and exciters. The latter, are the ones that are responsible for making us appreciate according to the stimuli we receive, what we consider is important while inhibitors reduce the impulse of what does not interest us. This is how it is achieved that sometimes we see only what we think is key, discarding what we do not consider useful.
Neurons according to the transmission of nerve impulse
As we explain at the beginning, neurons secrete a neurotransmitter to carry out synaptic activity and transmit impulses. Now, the neuron that is responsible for expelling it is known as a pre -aptic neuron, while the one in charge of receiving it is called postsinapic neuron.
conclusion
There are hundreds of neurons that fulfill various functions in our body and make us react as we do. Each is important as well as the release of their respective neurohumores. The increase or alteration of any of them is significantly noticeable in our health or mood such as dopamine or serotonin just by citing some key examples.
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