1) The sensory organs detect stimuli in the environment. The main senses in humans are sight, touch, smell, taste, and hearing. Each sense is associated with a specific sensory organ.
2) The skin is the sensory organ for touch. It contains receptors that detect changes in pressure, temperature, pain, and other stimuli. The skin has two main layers - the epidermis and dermis.
3) Smell receptors in the nose detect chemicals in inhaled air. The nose has a nasal cavity lined with mucus and smell receptors. When we smell something, sensory cells in the nose send signals to the brain.