Definition of Nervous Tissue

The nervous system acts as a master network within our body, collecting and processing information that travels to and from all corners of the body, from the smallest organs to the brain and vice versa. The organs of the nervous system are made up of nervous tissue.

We, like all other animals, are capable of autonomous movements. Our organs are in constant operation and everything must be perfectly coordinated, nothing can fail (for example, a "failure" of a couple of minutes in the heart could cause the death).

We do not have to be aware or remember that we must breathe or that the heart must beat, but we do not stop breathing for a minute. Are autonomous functions they are performed under very precise control, even while we are asleep. We can process information from outside and come up with sophisticated responses in a process known as response to stimuli and we have an intellectual capacity that allows us to think, use tools and communicate. All these functions are carried out by one of the most sophisticated organ systems in the living world: the nervous system, which is present in all animals, but its development and capacities reach their maximum in humans.

cells of the nervous tissue

The elementary units of the nervous system are the neurons. Neurons are highly specialized cells, and in their specialization process, they have acquired some characteristics that make them unique. Unlike other cells, the cell body of neurons has branch-like extensions called dendrites and axons.

The dendrites are the shorter branches, and usually each cell has several, unlike the axon, which is a longer branch and there is only one. The set of dendrites and axons gives the set an appearance of a star or a tree, where the trunk would be the axon and the dendrites would be the branches.

In functional terms, dendrites are the "antennae" of neurons, and receive information from other neurons or from the nearby environment, while the axon is “the data cable” that transmits the signals generated by the neuron to other neurons, muscle cells or glands.

In addition to neurons, in nervous tissue there are also other cells known as glial cells or neuroglia.

Glial cells are essential for the proper functioning of neurons and the nervous system as a whole. They provide structural support, nutrition, and electrical insulation for neurons. Among the different types of glial cells, we can find astrocytes, oligodendrocytes, and microglia cells.

astrocytes are star-shaped cells that play a crucial role in the supply of nutrients and oxygen to neurons and are responsible for maintain the blood brain barrier, which is the membrane that covers the entire central nervous system.

For any substance to reach a nerve organ, it must pass through the blood-brain barrier, including oxygen, nutrients, and water. It is an effective protective measure to prevent harmful substances (metabolic waste or toxic substances) and pathogens (viruses and bacteria) that could be circulating in the blood reach the central nervous system, and it is the only set of organs in the body that has such a measure of protection.

Astrocytes also clean the brain, eliminate dead neurons and have an active role during neuronal growth, since they They are responsible for guiding developing neurons to adopt the appropriate shape.

Oligodendrocytes and Schwann cells are responsible for the formation of myelin, a fatty substance that wraps around the axons of neurons, forming an insulating capsule that accelerates the speed of transmission of nerve impulses.

Microglia cells are immune cells, and make up the immune system of the nervous system. Its function is to eliminate pathogens and damaged cells.

Nerve impulse

In addition to the particular shape of neurons, another of their unique characteristics is that they are capable of communicating with each other through electrical impulses, called nerve impulses.

The electrical communication of neurons is one of the fastest between cells. An order sent from the brain to the feet can arrive in a couple of tenths of a second, from the In the same way, a tactile stimulus that we perceive on the sole of the foot reaches the brain.

When a neuron is stimulated, it generates a electrical signal that travels along its axon and reaches its end. In this part of the axon is a specialized structure called synaptic terminal.

At the synaptic terminal, the electrical signal causes the release of chemicals called neurotransmitters into the space between presynaptic neuron (the one that releases neurotransmitters) and the postsynaptic neuron (the one that receives the signal).

Neurotransmitters traverse this gap and bind to specific receptors on the cell body or on the dendrites of the postsynaptic neuron. When this happens, the neuron will generate its own nerve impulse, which will travel down its axon to the end and cause neurotransmitters to be released.

This process of nerve impulse transmission is repeated throughout the neural network, allowing fast and efficient communication between different areas of the body. Each neuron can have connections with thousands of other neurons, giving rise to complex networks that process information and coordinate actions.

Sometimes, a neuron does not communicate with another neuron, but with striated muscle cells, which are responsible for making movements.

The neurons that carry the orders to trigger the movements, called motor neurons, are directly connected to the cells of the striated muscle tissue. When the message reaches the end of the neuron, the neurotransmitters trigger the muscle cell to contract.