Master Vestibular System

What is the vestibular system?

It’s a sensory system located in the inner ear that controls balance and coordination of head and eye movements

What is the name of the enlarged base inside the semicircular canals?

Ampulla

What part of the semi-circular canals are embedded with hair cells?

Cupula

What is the main function of the semi-circular canals?

To detect rotation of the head e.g. turning the head side to side

What is the name of the fluid inside the ampulla?

Endolymph fluid

What happens to the cupula during head rotation?

The cupula deflects and bends the hair cells

What generates when the hair cells bend inside the ampulla?

Receptor potential

What is receptor potential?

A graded change in membrane potential produced in a sensory receptor cell in response to a stimulus

Try and explain the pathway of the semi-circular canals? What are the 4 steps?

1. The head rotates

2. A force is created by the fluid in the semi-circular canals

3. The hair cells bend due to the force created by the fluid

4. A receptor potential and action potential is created at the ampullary nerve and feeds into and becomes a branch of the 8th cranial nerve which goes to the brainstem.

What type of organs are the utricle and saccule?

Otolithic organs

Where are the hair cells found inside the utricle and saccule?

Epithelial walls of the macula

What is the gelatinous substance which the hair cells are embedded in?

Otolithic membrane

What type of crystals are located on top of the otolithic membrane?

Calcium carbonate crystals (otoconia)

What is the main function of the utricle and saccule?

To detect linear acceleration and head position relative to gravity e.g. tilting the head up and down

Try and explain the pathway of the utricle and saccule? What are the 5 steps?

1. The head tilts or accelerates/decelerates

2. Gravity from the tilt causes the otolithic membrane to shift

3. The hair cells bend

4. Action potential is generated

5. Finally the receptor potential and action potential is sent to the central nervous system to be processed.

What is linear acceleration?

The rate at which an object’s velocity changes as it moves along a straight-line path.

What do the hair cells synapse onto during the vestibular system and where is it located?

The bipolar first order neurons located in the scarpa’s ganglion

What is the vestibular-ocular reflex?

This reflex produces eye movement that counteracts head movement which then enables your gaze to remain locked onto a particular point.

E.g. focusing on an object while walking

What is the vestibulospinal reflex?

This reflex allows us to maintain/regain postural control by activating the vestibulospinal pathways.

E.g. you trip and the bending of the hair cells in your ear cause the vestibulospinal tracts to be activated which help you maintain your balance and upright posture.

What is the righting reflex?

This reflex restores the normal upright orientation of the head and body when it gets displaced

e.g. if you get knocked off balance, the reflex forces the head and the body back into vertical alignment.

What does the lateral vestibular tract control?

All limbs below the head and neck

What does the medial vestibular tract control?

Head and neck muscles

What does the gamma systems do in the vestibular system?

They control and modulate muscle tone

Where does information go after the muscle has received the information?

To the spinocerebellum