Central wrapping is done by:

Primary sensory nerve fiber belongs to type Iα (Aα) nerve fiber. Each sensory (afferent) nerve fiber has two branches. One of the branches supplies the central portion of nuclear bag  fiber. The other branch ends in central portion of the nuclear chain fiber. These branches end in the form of rings around central portion of nuclear bag and nuclear chain fibers. Therefore, these nerve endings are called annulospiral endings.