Living things react to environmental stimuli. Changes in environmental conditions, such as sounds, shocks, heat and cold, are perceived by the body, which reacts by adopting a posture corresponding to the stimulus.
Although it is the muscles that respond to the stimuli, it is the nervous tissue that is responsible for their reception and the choice of the appropriate response.
Nervous tissue has an ectodermal origin, in it the intercellular substance practically does not exist. The main cellular components are the neurons and glial cells.
The cells of glia or neurogy are several cell types related to the sustaining and nourishing neurons, producing myelin and phagocytosis.
Neurons, or nerve cells, have the property of receiving and transmitting nerve stimuli, allowing the body to respond to changes in the environment. The neurons are elongated and may, in some cases, reach about 1 meter in length, as in neurons that extend from our back to the foot. They are cells formed by a cell or pericary body, from which two types of prolongation depart: dendrites and axon.
The dentites These are branched cell extensions that are specialized in receiving stimuli, which can also be received by the cell body. The nerve impulse is always transmitted in the sense dendrite - body - axon.
O axon It is a thin, elongated, constant diameter cell expansion with branches in its final portion, so that the pulse can be transmitted simultaneously to multiple destinations. It is a structure that specializes in the transmission of nerve impulses to other neurons or to other cell types, such as effector organ cells (muscle and glandular).