Of ectodermal origin, the nervous tissue has the main function of receiving information from the external and internal environment, processing it and sending responses to organs and glands. It is thanks to this fabric that we are able to read this text and understand it.
Nervous tissue has little intercellular substance and is mainly composed of two cell types: neurons and glial cells, also called gliocytes.
Neurons, also called nerve cells, are responsible for transmitting the nerve impulse. These cells have three basic and distinct parts: the cell body, dendrites and axon.
It is in the cell body that the organelles and the nucleus are found. Among the cell organelles found in the cell body, we can mention the endoplasmic reticulum, ribosomes, Golgi complex, mitochondria and lysosomes. The endoplasmic reticulum added to the ribosomes is involved in major protein synthesis and forms the formerly called substance of Nissl.
It is from the cell body that two extensions called dendrites and axons depart. Dendrites are branched processes that have organelles as well as the cell body, not just the Golgi complex. They are related to the capture of the nerve impulse.
The axon is a long extension responsible for carrying the nerve impulse to a muscle cell, gland or other neuron. They lack Golgi complex and ribosomes.
It is important to note that in a neuron the nerve impulse will always follow the dendrite, cell body and axon direction.
In addition to neurons, nervous tissue is composed of glial cells, which comprise astrocytes, oligodendrocytes, microgliocytes and ependymal cells. Astrocytes are star-shaped and are mainly related to neuron nutrition. Oligodendrocytes are involved in the formation of the myelin sheath around the axon, thus allowing for faster nerve impulse conduction. Microgliocytes are involved in protecting the nervous system by carrying out phagocytosis. Finally, we have the ependymal cells, which have the function of lining the cavities of the brain, as well as the spinal canal.