A stimulus is an external or internal signal capable of causing a reaction in a cell or organism.
Sensitivity to a specific receptor called tropism or nasty in plants (depending on whether the reaction is permanent or temporary) and vertebrate taxism, on the other hand; They have structures of a nervous nature (receptors) specialized in capturing or receiving certain information that is produced in the environment, sending the information, through the sensory nerves, to the nerve centers to produce sensations (visual, tactile, painful, sound). , gustatory, olfactory, thermal or sensitive, among others).