Vestibular System Function and Dysfunctions Flashcards

Vocabulary flashcards covering vestibular system functions, vestibulospinal tracts, the vestibulo-ocular reflex, autonomic connections, reticular formation relationships, signs of impairment, motion sickness, and occupational performance implications.

Vestibular System Functions

The core functions of the vestibular system, which include maintaining equilibrium, maintaining balance, maintaining the head in an upright vertical position, coordinating head and eye movements via the vestibulo-ocular reflex (VOR), and influencing muscle tone through motor neurons and the vestibulospinal tracts.

Vestibulospinal Tract

An extrapyramidal, ipsilateral motor pathway originating in the vestibular nuclei of the medulla that provides unconscious motor control, regulates muscle tone, and innervates extensor (antigravity) muscle groups responsible for posture and stance.

Decerebrate Rigidity

A condition caused by damage in any brainstem tract where the vestibulospinal tract fires without modification from the brainstem and cortex, causing spasticity of upper and lower extremity muscles and carrying a much poorer prognosis than decorticate rigidity.

Vestibulo-Ocular Reflex (VOR)

A reflex that integrates sensory information from inner ear CN 8 (Vestibulocochlear) and communicates with motor CNs 3, 4, and 6 to reflexively produce eye movements in the exact opposite direction of head movement to stabilize an image on the retina.

Impaired VOR Symptoms

Deficits resulting from impaired vestibulo-ocular reflex, characterized primarily by blurred vision and difficulty reading during head or body movement.

Reticular Activating System

A brainstem structure responsible for excitatory and inhibitory functions that integrates vestibular input and screens sensory information to alert the brain to attend to incoming sensory data.

Inhibitory Vestibular Input

Vestibular stimulation, such as slow rocking, that is integrated by the reticular formation to calm the brain and body.

Excitatory Vestibular Input

Vestibular stimulation—such as fast dancing, rotary acceleration (spinning), and linear acceleration (riding roller coasters)—integrated by the reticular formation to arouse the brain and body.

Autonomic Nervous System Vestibular Connection

The connection mediated by CN 10 (vagus nerve) and its visceral branches to and from the gastrointestinal tract, which explains why vestibular overexcitation can induce nausea and vomiting.

Signs and Symptoms of Vestibular Impairment

Clinical presentations of PNS and CNS vestibular dysfunction, which include nystagmus, tinnitus, vertigo, hearing loss, loss of balance/falls, broad-based stance, sweating, nausea, and vomiting.

Motion Sickness

A vestibular disorder caused by repeated rhythmic stimulation (such as car, plane, or boat travel) presenting with vertigo, nausea, vomiting, lowered blood pressure, tachycardia, sweating, and potential postural hypotension and fainting due to blood pooling in the lower extremities.

Occupational Challenges in Vestibular Loss

Difficulties maintaining balance that occur when visual or proprioceptive sensory inputs are altered or missing, such as walking on sand or in dim lighting, or attempting to read during head movement.