Vestibular System

Overview of Vestibular System

1. Detects motion of head in space to control head and body posture and eye movement

2. Provide subjective sense of movement and orientation in space

The Vestibular system

The Maculae are responsible for (linear acceleration forces) Detecting Orientation of the Head with Respect to Gravity

The Maculae are in the

– Saccule : is responsible for

vertical acceleration

– Utricle: Is responsible for

horizontal acceleration

Saccule

Utricle

Vestibular Hair Cells

Macule and Hair Cell

Vestibular transduction of Mechanical Stimuli

Morphological polarization of hair cells in the utricular and saccular maculae

Forces acting on the head and the resulting displacement of the otolithic membrane of the utricular macula

Response of a vestibular nerve axon from an otolith organ

Vestibular Navigation

The Semicircular Canals Detect Angular Accelerations

The ampulla is responsible for the change in rotational movement

Vestibular Inputs

Posture and Balance

Postural adjustments require anticipatory motor actions.

Anticipatory maintenance of body posture

Anticipatory motor action in response to postural disturbance

Appropriate anticipatory responses to postural disturbances can be learned

Adaptive Postural Control Is Learned During Locomotion

The vestibular contribution to postural adjustment depends on whether the primary perturbation is to the feet or the head

Decerebrate Rigidity

Upper Motor Neurons That Maintain Balance and Posture