The Trochlear Nerve and How It Relaxes

The trochlear nerve is part of a complex hierarchy of cranial nerves that are important in humans’ perceptive, motor, and sensory processes. This nerve’s exact location is not well understood, though it is thought to run along the posterior superior or temporal part of the skull. The branch that it comes from is unknown. It innervates the major muscle groups of the face, head, and neck. The trochlear nerve also innervates the muscles of speech production, meaning it may help trigger speech production. The only other known function is that it may signal pain in the head.

Trochlear nerve branches:

The trochlear nerve branches off its main body, the acromion, and travels down the spine’s length. Along its way, it joins the components of the vestibular system, which help to balance the head and body, and the superior ophthalmic nucleus (Vagus nerve). The branch that it comes from eventually branches off into four general areas; the common body region (posterior-axillary area), the central neck, the face/neck area, and the ear region. It has been postulated that the trochlea may originate inside the ear; however, this remains proven. All branches of this complex have a vital role in the sensory processing of sound.

Vibration from inside the brain to the ear produces sounds, which depends upon the frequency of the vibration of cells present in the superior cervical ganglion. Cells in the trochlear nerve are sensitive to stretching, bending, and oscillating action, particularly in the anterior midbrain (mandala) and in the posterior parietal area. The exact function of this nerve is unknown; however, it appears to impact the auditory cortex of our brain. In particular, stimulation from the VLF (Vestibular Phosphorylation Function) group of neurons within the superior cervical ganglion result in the rise in recorded sounds (or auditory evoked response) in VLF neurons. In VLF, a decline in the strength of action potentials can be observed during a period of inactivity in the brain.

Superior cervical ganglion:

Neurons within the superior cervical ganglion respond to action rhythms of varying frequencies (i.e., beat frequency) from the brainstem, which then carries these rhythms to the neurons of the auditory cortex for further processing. Thus, different rhythms from different locations in the brain may be processed by the same cells in different areas of the cortex.

For example, auditory cortex neurons are responsive to beat rhythms, which travel from the anteriorly located cortex to the middle ear, and thus, may be processed in the auditory system. The cn vi fibers, on the other hand, are responsive to orientations of the head relative to gravity, which may again be processed in the superior cervical ganglion.

Superior colliculus, superior cervical ganglion:

Subsequently, the superior colliculus, superior cervical ganglion, and the basal ganglia reach the brain stem for maintenance of axon conductance. The inferiorly communicating superior cervical ganglion sends inputs to the superior cervical ganglion for muscular activity (such as swallowing, chewing, yawning, etc.), while the basal ganglia reach the brain for posture guidance.

The Trochlear Nerve innervates twelve muscles, all of which are located in the inner ear. These include the vestibular acuity, cervical ganglion, cranial osteoderms, middle ear bones, middle ear floor, and the associated superior oblique muscle. The superior oblique muscle originates in the area between the cervical spine and the external auditory canal. It then inserts onto the upper part of the chicory muscles and the external auditory nerve.

The trochlear muscle passes through three important structures: the common follicular tendon, the common tendinous ring, and the ovary. The common tendinous ring is the only part of the nerve that reaches the skin. The most common nerve entry site is in the ear canal, especially where it crosses the superior cervical ganglion. The internal ostium, which is located between the superior cervical ganglion and the cranial cavity, receives signals from the trochlear nucleus, which originates in the middle ear bones.

Ophthalmic cord:

The internal ophthalmic cord includes the retinal ganglion, the corneal vein, and the pupil. The retinal ganglion supplies vision to the retina. The corneal vein supplies blood to the eyelids and other facial muscles. The eye receives messages from the brain through the optic nerve and the internal ophthalmic nerves. The superior oblique muscle originates in the middle of the forehead above the eye. In addition to providing visual feedback, the superior oblique muscle helps with hand movement, facial expression, head movement, facial expression, and eye movement.