Human sensory organs

• Stimuli and responses in humans involve the ability to detect a stimulus through touching, smelling, tasting, hearing, and seeing
• Different sensory organs detect each stimulus: skin for touch, nose for smell, tongue for taste, eyes for sight, and ears for hearing
• Eyes are sensitive to light, ears to sound and balance, nose to chemicals in the air, tongue to chemicals in food, and skin to touch
• The human eye consists of structures like sclera, iris, pupil, conjunctiva, aqueous humor, cornea, suspensory ligaments, ciliary muscle, eye lens, choroid, retina, optic nerves, blind spot, and vitreous humor
• The retina contains photoreceptors called rod cells sensitive to light intensity and cone cells sensitive to colors (red, green, blue) under bright conditions
• Blinking spreads tears in the eyes to keep them moist and clean, containing chemicals that can kill bacteria