Nervous System VIII

Question 1

Briefly describe external ear

Answer 1

Auricle(Pinna)
-elastic cartilage

External auditory canal

• Curved tube that lies in the temporal bone
• leads from auricle to eardrum

Ear drum(tympanic membrane )

• thin semitransparent
• partition between external auditory canal & the middle ear

Ceruminous glands

• Specialized sebaceous glands
• secrete earwax (cerumen)

Question 2

What are the components of the middle ear?

Answer 2

Auditory ossicles

Tympanic membrane

Skeletal muscles

Eustachian tubes

Question 3

What are the auditory ossicles?

Answer 3

Three smallest bones in the body

Connected by synovial joints

1. Malleus -attached to internal surface of eardrum
2. Incus- middle bone, articulates with head of the stapes
3. Stapes- base fills into the oval window

Question 4

What is a tympanic membrane?

Answer 4

• separates external acoustic meatus from middle ear
• irregular cone shape

3 layers

• skin of etermal acoustic meatus
• collagen fibers
• mucous membrane of middle ear

Question 5

What skeletal muscles are of the middle ear?

Answer 5

Tensor tympani

• limits movement and increases tension on eardrum
  
  • CN V, mandibular branch

Stapedius

• smallest skeletal muscle
• dampens large vibrations of the stapes
  
  • decreases sensitivity of hearing CN VII

Question 6

What is the Eustachian tubes?

Answer 6

• Auditory (pharyngotympanic tube
• Connects middle ear with the nasopharynx
• Equalizes middle ear & atmospheric pressure

Question 7

What are the 2 divisions of the internal ear?

Answer 7

-Outer bony labyrinth
     series of cavities in the temporal bone
    -3 areas
         -Semicircular canals 
         -vestibule
         -cochlea
       Lined with periosteum
       Contains perylymph 
-Inner membranous labyrinth 
    -lined by epithelium 
    -contains endolymph

Question 8

Describe the vestibule of the internal ear

Answer 8

• Oval, central portion of bony labyrinth
  
  • Utricle
  • Saccule
  • Semicircular canals
    
    • Anterior
    • Posterior
    • Lateral
    • Ampulla
  • Oval window

Question 9

Summarize the internal ear

Answer 9

Cochlea-2.5 turns around the bony modiolus

Vestibulocpchlear nerve(CN VIII)

- Vestibular branch 
    - Ampullary nerve
    - Utricular nerve
   - Saccular nerve
   - Vestibular ganglion 
        - Cell bodies of sensory neurons

• Cochlear branch
  
  • Spiral ganglion
    
    • Cell bodies of sensory neurons

Question 10

Describe cochlea

Answer 10

• Bony, spiral canal
• 3 channels
  
  • Scala vestibuli
    
    • perilymph
  • Scala tympani
    
    • perilymph
  • Helicotrema
    
    • Apex of cochlea
  • Scala media (cochlear duct)
    
    • Endolymph
    • Vestibular membrane
    • Basilar membrane
    • Spiral organ of Corti

Question 11

Describe Organ of Corti

Answer 11

Coiled sheet of epithelial cells
    ~16000 hair cells 
          -Receptors for hearing 
          -Inner hair cells
             -Single row
          -Outer hair cells
             -3 rows
       -Supporting cells 

Tectorial membrane
-flexible, gelatious membrane

Question 12

Summarize the physiology of equilibrium

Answer 12

• Otolithic organs.
  
  • saccule
  • utricle

2 Maculae

• perpendicular to each other
• Receptors for static equilibrium
  
  • Contribute to dynamic equilibrium
• Hair cells
  
  • sensory cells
• Supporting cells
• Otolithic membrane
  
  • Rests on hair cells
  • Contains otoliths
    
    • Layer of dense calcium carbonate crystals

Question 13

What is the function of the external (outer) ear?

Answer 13

Auricle (pinna): Collects sound waves

External auditory canal (meatus): directs sound waves to the eardrum

Tympanic membrane (eardrum): sound waves cause it to vibrate, which in turn causes the malleus to vibrate

Question 14

What are the functions of the middle ear?

Answer 14

Auditory ossicles: Transmit and amplify vibrations from tympanic membrane to oval window

Auditory (Eustachian tube): equalizes air pressure on both sides of the tympanic membrane

Question 15

What are the function of internal (inner) ear?

Answer 15

Cochlea: Contains a series of fluids, channels, and membranes that transmit vibrations to the spiral organ (organ of Corti), the organ of hearing; hair cells in the spiral organ produce receptor potentials, which elicit nerve impulses in the cochlear branch of the vestibulocochlear (VIII) nerve.

Vestibular apparatus: includes semicircular ducts, utricle and saccule, which generate nerve impulses that propagate along the vestibular branch of the vestibulocochlear (VIII) nerve

Semicircular ducts: contain Cristae, site of hair cells dynamic equilibrium (maintenance of body position, mainly the head, in response to rotational acceleration and deceleration )

Utricle: contains macula, site of hair cells for static equilibrium (maintains body position, mainly the head, relative to the force of the gravoty)

Saccule: Contains macula, site of hair cells for static equilibrium (maintenance of of body position, mainly the head, relative to the force of gravity )

Question 16

Summarize olfaction

Answer 16

Sense of smell

Olfactory epithelium

 - 3 types of cells
      - olfactory receptors
          - olfactory hairs
      - Supporting cells
      - Basal stem cells

Question 17

Summarize Gustation

Answer 17

Sense of taste

5 primary tastes
    -All flavors are a combination of the 5 primary
      1. Sour
      2. Sweet
      3. Bitter
      4. Salty
      5. Umami
          -Meaty, savory
Taste buds
-Guststory sensory cells
    -Gustatory hair
-Supporting cells
-Basal cells