Tonic water and is used mostly for its flavor. As a result of the lower quinine content, it is less bitter, and is also usually sweetened, often with high-fructose corn syrup or sugar. Some manufacturers also produce diet (or slimline) tonic water, which may contain artificial sweeteners such as aspartame. Traditional-style tonic water with little more than quinine and carbonated water is less common but may be preferred by those who desire the bitter flavor. In the United States, the US Food and Drug Administration (FDA) limits the quinine content in tonic water to 83 ppm (83 mg per liter if calculated
Tonic (physiology) joint capsule, muscle spindle and the Ruffini corpuscle. Tonic (physiology) Tonic in physiology refers to a physiological response which is slow and may be graded. This term is typically used in opposition to a fast response. For instance, tonic muscles are contrasted by the more typical and much faster twitch muscles, while tonic sensory nerve endings are contrasted to the much faster phasic sensory nerve endings. Tonic muscles are much slower than twitch fibers in terms of time from stimulus to full activation, time to full relaxation upon cessation of stimuli, and maximal shortening velocity. These muscles are rarely found