Exam 3 Week 14 ppt 7 hair cells

Question 1

two main divisions of both the bony & membranous Labyrinth

Answer 1

Cochlear

Vestibular

Question 2

What is the Osseous labyrinth

Answer 2

series of bony cavities and channels within the petrous part of the temporal bone

Question 3

What is the membranous labyrinth?

Answer 3

series of Fluid filled communicating ducts & sacs within the bony labyrinth and Secured to bony labyrinth by fibrous bands

Question 4

Purpose of membranous labyrinth

Answer 4

preserves the basic form of the osseous labyrinth

Question 5

What is the perilymph

Answer 5

• Fluid separating osseous & membranous labyrinth

- Contiguous with cerebrospinal fluid of subarachnoid space via peri-lymphatic duct

Question 6

What is the endoilymph?

Answer 6

• Fluid within membranous labyrinth

- Same ionic composition as intracelluar fluid

Question 7

How is endoilymph formed?

Answer 7

specialized secretory cells of the membranous labyrinth

Question 8

How is endolymph removed?

Answer 8

specialized cells of endolymphatic sac

Question 9

How are receptor cells of both vestibular & auditory systems very simlar?

Answer 9

when activated Secrete neurotransmitters to excite terminal endings of vestibulocochlear nerve (CN VIII)

Question 10

How are the hair cells structurally polar?

Answer 10

• Single large kinocilium
• 60-100 smaller stereo-cilia arranged away from the kinocilium by decreasing height
• Kinocilium degenerates during development in cochlear receptor surface

I don’t understand this answer. They were the bullet points on the pp

Question 11

How are hair cells stimulated?

Answer 11

mechanical “bending” of cilia or hairs, but pivoting better term

Question 12

Why is pivoting a better term for hair cell stimuli?

Answer 12

Actin myofilament holds cilia stiff So cilium pivots at flexible base where connected to hair cell

Question 13

How is cilia displaced during stimuli?

Answer 13

Cilia bundle displaced as unit- held by top links.

Question 14

What happens when pivoting of cilia on hair cell depolarizes hair cell? (5)

Answer 14

1. Endolymph rich in K+ & poor in Na+ & positively charged compared to negative intra-cellular environment
2. Pivoting of cilia produces increased influx K+ into cell
3. Cell depolarization opens voltage-gated Ca++ channels
4. Increased intracellular Ca++ releases glutamate to activate primary afferent
5. Slight K+ current all the time so regular depolarization of hair cell and low frequency firing of primary afferent neurons

Question 15

Hair cell polarity- 3 points to remember

Answer 15

1. plays an important role in vestibular function
2. Stereocilia pushed toward kinocilium increases firing rate
3. Stereocilia pushed away from kinocilium decreases firing rate