Point 17
Motor V
Mesencephalic Nucleus V
This nucleus consists of a slender strand of
cells extending from the chief sensory nucleus through the
midbrain. The nucleus is located beneath the lateral edge of
the floor of the fourth ventricle in the pons and in the
lateral region of the periaqueductal grey matter in the
midbrain. These cells are incorporated into the neuraxis,
rather than being in the cerebrospinal ganglia (i.e., the
trigeminal ganglion, the geniculate ganglion, etc.). Most of
the peripheral processes of mesencephalic V neurons occupy
the motor root of the trigeminal nerve and are distributed
to muscle spindles in the muscles of mastication. The
central processes of mesencephalic V neurons terminate
within motor nucleus V. This connection establishes the
stretch reflex originating in the muscle spindles of the
masticatory muscles, together with a reflex for the control
of the force of the bite. The mesencephalic nucleus V may be
thought of as being similar to Clarke's column and the
accessory cuneate nucleus (i.e., unconscious
proprioception).