Sensation is the awareness of changes within or outside the body, either consciously or subconsciously. The conscious interpretation of a sensation is called perception. Only those sensations that are processed in the cerebral cortex, like hearing and smell, can be perceived, whereas other sensations, such as changes in heart rate, remain undetected. Sensory modalities can be grouped into two categories—general and special. General senses are those that are detected by sensory receptors throughout the body. They can be further classified into somatic and visceral senses. Somatic senses pertain to the external environment and are detected by receptors in the skin, muscles, and joints. These include the senses of temperature, pain, touch, pressure, vibration, and proprioception or body position. Visceral senses convey sensations related to internal organs, such as hunger and thirst. Special senses are those that are received by sensory neurons housed in specialized sense organs. These include sensory modalities of smell, taste, vision, hearing, and equilibrium or balance.