Pain
The pain signal travels from the periphery to the spinal cord along an A-delta or C fiber. Because the A-delta fiber is thicker than the C fiber, and is thinly sheathed in an electrically insulating material (myelin), it carries its signal faster (5-30 m/s) than the unmyelinated C fiber (0.5-2 m/s). Pain evoked by the (faster) A-delta fibers is described as sharp and is felt first. This is followed by a duller pain, often described as burning, carried by the C fibers. These first order neurons enter the spinal cord via Lissauer's tract.
How do first order neurons enter the spinal cord?
via Lissauer's tract
These first order neurons enter the spinal cord via Lissauer's tract.
the spinal cord