The extrinsic muscles in the model.

Each row of whiskers is attached to one superficial extrinsic protracting muscle, which represents Pars media superior (PMS) or Pars media inferior (PMI) of the M. nasolabialis profundus, for rows A–B or C–E, respectively. Each of the most rostral whiskers in rows A–B is also attached to a deeper extrinsic protracting muscle, which respresents the pseudo-intrinsic (PI) portions of the Pars interna of the M. nasolabialis profundus. The PI can be activated together with the PMS, or separately (by intrinsic MNs). In addition, each row is attached to two extrinsic retracting muscle groups: superficial retracting muscles and deep retracting muscles. The superficial retracting muscles represent M. nasolabialis (NL) and M. nasolabialis superficialis (NLS) for rows A–E. The deep retracting muscles represent Pars interna profunda (PIP) of the M. nasolabialis profundus for rows A–B, and Pars maxillaris profunda (MP) and Pars maxillaris superficialis (MS) of the M. nasolabialis profundus for rows C–E.*Attached only to whiskers A4 and B4.