Adequate stimulus
a stimulus to which a particular receptor responds effectively and that gives rise to a characteristic sensation; e.g., light and sound waves that stimulate, respectively, visual and auditory receptors.
A sensory system is a part of the nervous system consisting of sensory receptors that receive stimuli from the internal and external environment, neural pathways that conduct this information to the brain and parts of the brain that processes this information. Know the different sensory systems of the human body as elaborated by this tutorial...