Final answer:
A-beta fibers are the nerve fibers responsible for sensing touch in the medial dorsal horn of the spinal cord. They are fast, heavily myelinated, and play a significant role in the sensation of touch and proprioception.
Step-by-step explanation:
The type of nerve fibers that sense touch in the medial dorsal horn of the spinal cord are A-beta fibers, which are fast, heavily myelinated fibers. These fibers are responsible for transmitting the sensation of touch, as well as proprioception, which is the sense of the relative position of body parts. The A-beta fibers are one of the types that contribute to the dorsal column system, which primarily carries information related to touch and proprioception to the brain. Other types of nerve fibers include A-alpha, which are involved in motor function, A-delta, which are associated with sharp, acute pain, and C fibers, which are responsible for transmitting slow, chronic pain, temperature, and certain kinds of touch.