What are the 4 vestibular pathways?

there are 4 important vestibular pathways to consider:

• the primary sensory pathway from the vestibular nuclei (particularly the superior and lateral) to the VP nucleus of the thalamus and then to cortex.
• vestibulospinal reflexes.
• the vestibulo-ocular reflex (VOR)
• vestibulo-cerebellar connections.

What is the first order neuron of the vestibular pathway?

Vestibular ganglion It is a cluster of bipolar sensory neurons, that are the first-order neurons of the vestibular pathway. The peripheral processes of vestibular ganglion cells comprise the nerve fibers that receive the stimuli from the hair cells of the otolithic organs and semicircular canals, respectively.

How does the vestibular ocular reflex work?

The Vestibulo-Ocular Reflex. The vestibulo-ocular reflex (VOR) uses information from the vestibular labyrinth of the inner ear to generate eye movements that stabilize gaze during head movements. Without the VOR, when walking down the street, it is impossible to read signs or even recognize faces.

Where does vestibular information goes first?

The 1st order vestibular afferents arise in Scarpa’s ganglion, which is in the distal portion of the internal auditory meatus. The axons travel in the vestibular portion of the VIIIth cranial nerve and enter the brain stem at the pontomedullary junction.

What are vestibular projections?

Descending projections from the vestibular nuclei are essential for postural adjustments of the head and body. This pathway regulates head position by reflex activity of neck muscles in response to stimulation of the semicircular canals from rotational accelerations of the head.

Which five organs make up the vestibular system?

There are five vestibular receptor organs in the inner ear: the utricle, the saccule, and three semicircular canals. Together, they make up what’s known as the vestibular labyrinth that is shown in Figure 1. The utricle and saccule respond to acceleration in a straight line, such as gravity.

Where is located the body of the 3rd neurons of the vestibular nerve?

Axons of the vestibular nerve synapse in the vestibular nucleus are found on the lateral floor and wall of the fourth ventricle in the pons and medulla. It arises from bipolar cells in the vestibular ganglion which is situated in the upper part of the outer end of the internal auditory meatus.

What is the Cervico ocular reflex?

The cervico-ocular reflex (COR) is an ocular stabilization reflex that is elicited by rotation of the neck. It works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina due to self-motion.

How do you elicit a doll’s eye reflex?

Typically the doll’s eyes reflex is elicited by turning the head of the unconscious patient while observing the eyes. The eyes will normally move as if the patient is fixating on a stationary object. If there is a negative doll’s eyes reflex then the eyes remain stationary with respect to the head.

Where does the Vestibulospinal pathway start and end?

Medial vestibulospinal fibers join with the ipsilateral and contralateral medial longitudinal fasciculus, and descend in the anterior funiculus of the spinal cord. Fibers run down to the anterior funiculus to the cervical spinal cord segments and terminate on neurons of laminae VII and VIII.

Where is vestibular located?

the inner ear
vestibular system, apparatus of the inner ear involved in balance. The vestibular system consists of two structures of the bony labyrinth of the inner ear, the vestibule and the semicircular canals, and the structures of the membranous labyrinth contained within them.

What are the vestibular receptors?

The vestibular receptors lie in the inner ear next to the auditory cochlea. They detect rotational motion (head turns), linear motion (translations), and tilts of the head relative to gravity and transduce these motions into neural signals that can be sent to the brain.

What is the function of the vestibulo-ocular reflex?

The vestibulo-ocular reflex is an involuntary motor activity mediated by the vestibular system which serves for adjusting the eye movements while the head moves in the horizontal plane. It serves for fixing the gaze during head repositioning.

Is the horizontal vestibulo–ocular reflex (VOR) linear or nonlinear?

Previous work in squirrel monkeys has demonstrated the presence of linear and nonlinear components to the horizontal vestibulo–ocular reflex (VOR). The nonlinear component is a velocity-dependent gain enhancement (see earlier discussion in the section titled ‘Stimulus-dependent VOR motor learning: behavior’).

What is the pathway of the medial vestibular tract?

This pathway helps us walk upright. The medial vestibular tract starts in the medial vestibular nucleus and extends bilaterally through mid-thoracic levels of the spinal cord in the MLF. This tract affects head movements and helps integrate head and eye movements.

How does the vestibular system work with the extraocular system?

This way, the vestibular system mediates the reflexive activity of the extraocular muscles. More precisely, the vestibular system mediates the vestibulo-ocular reflex, in which the movements of the eyes are adjusted to the movements of the head.