Nerve Ending

A Nerve Ending is a bizarre, static enemy that can appear on various floors. It does not attack.

Nerve Endings are one of the few enemies in the game that are completely stationary. They constantly sway back and forth and appear to be attached to a small pile of organ tissue on the ground with smaller Nerve Endings protruding. They usually act as meat shields for stronger enemies or are placed in unreachable areas where it's slightly harder to hit them. Although Nerve Endings do not attack, they can still do contact damage.

Nerve Ending 2
Nerve Ending 2 is an alternate, orange-tinted and more hostile Nerve Ending added in Afterbirth †. Nerve Ending 2 is stationary like regular Nerve Endings, but if Isaac gets too close, it will attack him by whipping itself at him.

Trivia

 * Nerve Endings share a similar shape and idle movement pattern with that of Pods from Dead Space, both swaying their tentacles and being stationary. Unlike Nerve Endings, however, Pods have small projectiles as damage.
 * It's possible that the Nerve Ending is a giant axon, an electrical impulse terminal for nerve cells, which could explain its name.