Nephritis is the most common cause of blood in the urine of children and young adults but it can occur at any age. If your GP suspects nephritis he will usually refer you to a nephrologist (kidney doctor).
Muscle fiber types can be broken down into two main types: slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. These fast twitch fibers can be further categorized into Type IIa and Type IIb fibers, which are also known as fast twitch oxidative and fast twitch glycolytic, respectively.
There are two types of peripheral nerve fibers, afferent and efferent. 1  Afferent fibers are those that carry neural impulses toward the central nervous system. 2  Efferent fibers carry impulses from the central nervous system to effectors such as muscles and glands.