Physiology Of Equilibrium And Balance

Question 1

Which parts of the brain is equilibrium processed?

Answer 1

Superior lateral inferior and medial Vestibular nuclei in the medula
- receive fibers directly from the CN 8

Flocculus of the cerebellum

Thalamus

Hypothalamus

Question 2

What do each of the different vestibular nuclei do specifically?

Answer 2

Superior and medial = control eye movements and make sure they stay centered
- receives direct information from the vestibular ganglion.

Lateral = control postural reflexes and ensure balance
- receives direct information from the utricle and saccule of the inner ear.

Inferior = same as lateral
- receives direct information from the semi-circular canals, utricle and saccular

Question 3

What’s another word for vestibular ganglion?

Answer 3

Scarpas ganglion

Question 4

What’s another word for otoliths? And how does linear acceleration and spatial orientation work?

Answer 4

Statoconia

They are calcium stones embedded in a gelatinous layer in the maculae and the ampullae of the semicircular channels

When the head moves, the otoliths move with gravity. This bends hair cells in a specific direction, which causes specific signals to be activated in hair nerve cells based on the direction of the bend.
- can excite or inhibt based on orientation for he numerous hair cells.

*nerve signals are always being sent, even at rest, just the amplitude and type of signal changes

Question 5

How does angular acceleration work

Answer 5

does not use otoliths like orientation

Endolymph pulls on the cupula within the semicircular canals opposite the direction of rotation

When the cupula bends, it excites the hair cells and triggers electrical impulses
- rotating to the right causes the right semicircular canals to be excited (lymph is pulling left) and the left semicircular canals to be inhibited (lymph is pulling right)

Question 6

How does vestibular angular rotation conduction occur

Answer 6

1) at rest the endolymph and perilymph are at 0 mV, the type 1 and 2 hair cells are at -40 mV and the hair cells are not bent
- the tonic level of discharge is 100/second

2) rotation begins and either induces positive or negative mechanical deformation
- a) positive: rotation towards the kinocilium (largest hair follicle) causes opening of K+ channels
- b) negative: rotation away from the kinocilium (largest hair follicle) causes closing of the K+ channels

3) in positive deformation, potassium rushes in and allows calcium to enter in as well

4) increased intracellular calcium causes exoctytosis of glutamate vesicles and an excitatory signal
- tonic discharge is 400/second