Sensory receptors are dendrites of sensory neurons or specialized receptor cells that detect external and internal stimuli. Sensory receptors are grouped into three structural categories. Sensory neurons with free nerve endings are the simplest kind of sensory receptors, while those with encapsulated nerve endings have a specialized capsule that enhances their specificity. Both of them detect stimuli for the general senses. In contrast, special senses are detected by receptor cells present inside sense organs that synapse with sensory neurons. Based on their location, sensory receptors can also be classified into exteroceptors, interoceptors, and proprioceptors. Exteroceptors, such as smell and hearing receptors, are located on or near the body's surface and provide information about the external environment. Interoceptors are present within the body and convey visceral information such as blood pressure or heart rate. Proprioceptors are located in muscles, tendons, and joints and provide information about body position and movement. Additionally, sensory receptors can be classified by their stimuli. Mechanoreceptors detect mechanical stimuli, thermoreceptors temperature, nociceptors pain, photoreceptor light, and chemoreceptors chemical concentration.