Neuroscience Lecture 22: Balance & Equilibrium

What organ detects changes in balance and equilibrium?

Ear

What are the two body movements that stimulate the receptors for equilibrium?

1. Linear acceleration/deceleration

2. Rotational acceleration/deceleration

What are the receptor organs for equilibrium called?

Vestibular apparatus

Which two parts of the vestibule are part of the vestibular apparatus?

1. Utricle

2. Saccule

Which part of the semicircular canals is part of the vestibular apparatus?

Semicircular ducts

What is the portion of the temporal bone that encases the vestibular apparatus?

Bony labyrinth

What are the membranous tubes and chambers within the bony labyrinth?

Membranous labyrinth

What is the functional portion of the vestibular apparatus?

Membranous labyrinth

What two senses are detected by the vestibular apparatus?

1. Position of head in space

2. Movement of head

What is the nerve that innervates the vestibular apparatus?

Vestibulocochlear

What is the thickened elevation in the semicircular canals?

Ampulla

What are hair cells embedded inside in the ampulla?

Cupula

What does the position of the three ampulla in the semicircular canal do?

Detection of rotational acceleration/deceleration

What is an individual hair cell in the semicircular canal called?

Stereocilium

What is the largest stereocilium called?

Kinocilium

What channels are the tips of stereocilium connected to?

Ca2+ channels

What fluid surrounds hair cells in the semicircular canal?

Endolymph

Are the calcium channels connected to hair cells partially open or closed in normal state?

Partially open

What is caused by open calcium channels that leads to partial depolarization in hair cells?

K+ enters

What is caused when the hair cells are bent towards the kinocilia?

Strong depolarization

What is caused when the hair cells are bent away from the kinocilia?

Hyperpolarization

What causes hair cells to bend in the opposite direction in the beginning?

Lag of endolymph and cupula

When are the signals in hair cells transmitted in movement?

Beginning and end

What is symmetry of semicircular canals in the head?

Mirror symmetric

How are hair cells aligned in mirror symmetric semicircular canals?

Oppositely

What is the utricle and saccule known as collectively?

Otolithic organs

Is the maculae of the utricle and saccule parallel or perpendicular to each other?

Perpendicular

In the upright position, is the macula of the utricle positioned horizontally or vertically?

Horizontally

In the upright position, is the macula of the saccule positioned horizontally or vertically?

Vertically

What are the two types of cells in the maculae of the utricle and saccule?

1. Hair cells

2. Supporting cells

What membrane is secreted by the supporting cells of the maculae of the utricle and saccule?

Otolithic membrane

What are the two names for the calcium carbonate crystals embedded in the otolithic membrane?

1. Otoliths

2. Statoconia

What do the bases and sides of the hair cells synapse with?

Sensory endings of vestibular nerve

How much greater is the specific gravity of the calcified statoconia to the surrounding tissues and fluid/

2 - 3x

Is the hair of the utricle or saccule bent in an upright position?

Saccule

Is the hair of the utricle or saccule bent while lying down?

Utricle

What are the three equilibrium pathways for balance?

1. Somatosensory/Proprioceptive

2. Vestibular

3. Visual

Which organ adjusts skeletal muscle tone and body posture to align with head position?

Spinal cord

Which muscles ensures balance between the head and body?

Neck muscles

Which organ performs rapid calculations to maintain balance?

Cerebellum

What is the involuntary eye movements that occur during rapid head motion called?

Nystagmus

What is the disequilibrium caused by damage to the bilateral vestibular apparatus?

Ataxia

Which ataxia has improved balance with visual input?

Sensory ataxia

Which ataxia does NOT have improved balance with visual input?

Cerebellar ataxia

What is the sickness caused by constant stimulation of the vestibular apparatus?

Motion Sickness

What condition is caused by damage to the vestibular apparatus?

Meniere's disease