The eighth, often neglected, but frequently problematic sensory system in SPD is the Interoceptive System. Interoception refers to sensations related to the physiological / physical condition of the body. Interoceptors are internal sensors that provide a sense of what our internal organs are feeling. Hunger and thirst are examples of interoception. Interoception detects responses that guide regulation, including hunger, heart rate, respiration and elimination. The Interoceptive stimulation is detected through nerve endings lining the respiratory and digestive mucous membranes. Interoception works the vestibular and proprioceptive senses to determine how an individual perceives their own body. Well-modulated interoception helps the individual detect proprioceptive and vestibular sensation normally. For example, if a person feels his/her heart pounding, while it is not comfortable, trauma from the stimulation is not likely; nor will the stimulation be craved. The same is true for hunger and thirst, as well as the feeling of the need to urinate or have a bowel movement.