Sense Organs and Sensory Perception

Your senses are your body’s means of making sense of the information your nervous system receives from inside your body and from the outside world (stimuli). Your senses enable you to adapt to change in your environment and survive. The sensory division of the peripheral nervous system is organized into highly developed sense organs, which are groups of tissues that work together in responding to a specific kind of stimulus. The sense organs correspond to a defined region within the brain where the nerve signals are received and interpreted. Your sense organs include your eyes, ears, nose, mouth, and skin. Sensory neurons send nerve impulses from sensory receptors to the central nervous system. The brain then interprets the nerve impulses to form a response. A sensory receptor is a cell, or a group of cells that detect stimuli. Types of receptor :

Sensory receptors can be classified based on the type of stimuli to which they respond.

• Mechanoreceptors respond to mechanical stimuli such as tension (stretching) or pressure. They tranduce mechanical energy into nerve impulses.



• Thermoreceptors respond to changes in temperature (heat and cold); they tranduce heat energy into nerve impulses.



• Nociceptors respond to injurious or painful stimuli; they tranduce a variety of forms of energy into nerve impulses.



• Photoreceptors respond to electromagnetic radiation, typically wavelengths of visible light, they tranduce light energy into nerve impulses; in humans (and most vertebrates), these are the rods and cones of the eyes.



• Chemoreceptor responds to chemical stimuli; they tranduce the binding of specific hemicals into nerve impulses; includes exteroceptors for smell and taste and interoceptors sensitive to concentration changes of some molecules in the blood.

It is generally agreed that there are at least seven different senses in humans. These are sight, sound, taste, smell, touch, balance, and body awareness (the sense of knowing where the regions of your body are located at any one time).