Activity 5: Microscopic Anatomy of the Equilibrium Apparatus and Mechanisms of Equilibrium

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1

The equilibrium receptors of the internal ear are collectively called what apparatus?

Vestibular apparatus

2

The equilibrium receptors or vestibular apparatus are found in which 2 bony labyrinth layers?

1. Vestibule

2. Semicircular canals

3

The vestibule contains what 2 saclike membranes?

1. Utricle

2. Saccule

4

The utricle and saccule membranes are filled with what fluid and contain what type of receptor cells?

Filled with endolymph and contain receptor hair cells.

5

The semicircular canals contain what membranous structures?

Semicircular ducts.

6

The semicircular ducts are filled with what fluid and contain what type of receptor cells?

Filled with endolymph and contain receptor hair cells.

7

The semicircular canals monitor what type of head rotation or balance?

Monitor rotational acceleration or rotational balance of the head.

8

Monitoring rotational acceleration of the head is called what type of equilibrium?

Dynamic equilibrium.

9

The semicircular canals measure what in circumference?

1.2 cm

10

At the base of each semicircular duct is what enlarged region?

Ampulla

11

Each ampulla contains a receptor region called what?

Crista ampulllaris

12

The crista ampullaris consists of a tuft of what type of cells covered with what?

Consists of a tuft of receptor hair cells covered with ampullary cupula.

13

Describe the texture of the ampullary cupula.

Gelatinous

14

The crista ampullaris responds to changes in the velocity of what type of head movement?

Rotational head movement.

15

Consider what happens with you twirling around.

  1. During acceleration when you begin to twirl, what happens to the endolymph in regard to head movement (i.e. speed)? What happens to the ampullary cupula of receptor hair cells (i.e. direction)?
  2. If the body continues to rotate at a constant rate, what will happen to the endolymph's speed? What happens to the ampullary cupula of receptor hair cells (i.e. direction)? Are hair cells still being stimulated? What sensation do you lose?
  3. When rotational movement stops suddenly, what happens to the endloymph in regard to head movement (i.e. direction)? What happens to the apullary cupula of receptor hair cells (i.e. direction)?

1. Inertia causes the endolymph to lag behind the head movement speed. This causes the ampullary cupula to be pushed in the opposite direction of head movement.

2.The endolymph comes to rest and moves at the same speed has head movement. The ampullary cupula returns to its normal, upright position. Hair cells are no longer stimulated, and you lose the sensation of spinning.

3.The endlolymph keeps moving in the direction of head movement. This causes the ampullary cupula to be pushed in the same direction of head movement.

16

1. When the ampullary cupula of receptor hair cells is pushed in the opposite direction of head movement, do you get depolarization of hyperpolarization?

2. Based on your answer above, is there increased or decreased transmission of impulse to the vestibular division of the eight cranial nerve to the brain?

3. Based on your answer to the 2 questions above, what sensation is felt?

1. Depolarization

2. Increased transmission of impulses to the vestibular division of the eighth cranial nerve

3. The sensation of spinning.

17

1. When the ampullary cupula of receptor hair cells is pushed in the same direction of head movement, do you get depolarization of hyperpolarization?

2. Based on your answer above, is there increased or decreased transmission of impulse to the vestibular division of the eight cranial nerve to the brain?

3. Based on your answers to the 2 questions above, what is your brain told, and what sensation do you feel?

1. Hyperpolarization

2. Decreased transmission of impulses to the vestibular division of the eighth cranial nerve.

3. Your brain is told that you have stopped moving and accounts for the reversed motion sensation you feel when you stop twirling suddenly.

18

Maculae in the membranous utricle and saccule also contain another set of what type of cells?

Receptor hair cells

19

Receptor hair cells in the maculae of the utricle and saccule monitor what 2 things?

1. Head position in a straight line

2. Linear acceleration or linear balance

20

The monitoring process by the receptor hair cells in the maculae is called what?

Static equilibrium

21

The maculae respond to what type of pull?

Gravitation pull

22

Responding to gravitation pull, the maculae provide information on what 2 things (Hint: direction and speed)?

1. Which way is up or down

2. Linear changes in speed

23

The receptor hair cells in each macula have steriocilia plus one ____ that are embedded in which membrane?

Plus one kinocilium that are embedded in the otolith membrane.

24

What type of texture is the otolith membrane?

Gelatinous material

25

The otolith membrane contains small grains of what compound, and what are they called?

Small grains of calcium carbonate called otoliths.

26

When the head moves, how do the otoliths move?

The otoliths move in response to variations in gravitation pull.

27

When otoliths deflect hair cells during movement, how are hyperpolarization and depolarization triggered?

Hyperpolarization: Stereocilia or hairs bend away from the kinocilium

Depolarization: Stereocilia or hairs bend toward the kinocilium

28

1. During depolarization of hair cells by otoliths, are nerve fibers excited or inhibited?

2. How are action potentials generated (in regard to speed)?

1. Excited

2. Action potentials are generated more rapidly.

29

1. During hyperpolarization of hair cells by otoliths, are nerve fibers excited or inhibited?

2. How are action potentials generated (in regard to speed)?

1. Inhibited

2. Action potentials decreased (below the resting rate of fire).

30

Do the receptors of semicircular canals and the vestiblue always act independently since they are responsible for dynamic and static equilibrium respectively?

No. They rarely act independently.

31

Processing of the hair cells from the semicircular canals and the vestiblue are complex and processed by what 2 brain features and involves input from what 2 things of the body?

Processed by the brain and cerebellum and involves input from proprioceptors and the eyes.

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