This theory states that there are two types of nerve fibers. They are the A-beta and C nerve fibers. The A-beta nerve fibers are large and fast conducting. The C nerve fibers are small and slow conducting. The theory states that when there is a high amount of impulses received, the A-beta fibers close the gate in the substantia gelatinosa and the painful impulses are prevented from passing in the C fibers. Acupuncture may work as a pain reliever by stimulating points that affect the A-beta nerve fibers. The needles may make a stream of painless impulses that transmit to the substantia gelatinosa which causes the gate to close and the pain impulses to stop.