5.4 STIMULUS

Any change or signal in the environment that can make an organism react is called a stimulus. (Plural: stimuli). Stimuli can be external or internal. External sensory stimuli generally activated by the external changes and include pain, touch, vision, smell, taste, sound, and balance. Internal stimulus is the type of stimulus that comes from inside of the body. One example is of hunger which makes our body get food as there is low energy in the body. Other example includes, level of glucose in the blood, blood pressure and homeostasis etc.