C15 - ear2

Question 1

Vestibular complex?

Answer 1

vestibule and semi-circular canals - general area

Question 2

Cochlea

Answer 2

Houses the membranous laby cochlear duct which houses the spiral organ/organ of corti

Question 3

Vestibular membrane

Answer 3

Forms the roof of the cochlear duct

Question 4

Basilar membrane

Answer 4

Forms the floor of the cochlear duct. Supports the spiral organ, anchors hair cells. Narrow and thick by the oval window - widens and thins as it approaches the cochlear apex.

Question 5

Scala vestibuli (vestibular duct)

Answer 5

Filled with perilymph, runs above cochlear duct, accepts pressure from abutting oval window

Question 6

Scala media (cochlear duct)

Answer 6

Membranous labyrinth that extends through the center of the cochlea

Question 7

Scala Tympani (tympanic duct)

Answer 7

Filled with perilymph, runs below cochlear duct, to round window, relieves pressure.

Question 8

Tectorial membrane

Answer 8

Gelatinous overhanging structure that the stereocilia extend into. Friction of hairs so they can create potentials.

Question 9

Helicotrema

Answer 9

Apex of the cochlea where the scala vestibuli and scala tympani merge.

Question 10

Spiral organ (of Corti)

Answer 10

Thick, sensory epithelium within the cochlear consisting of both hair cells and supporting cells that rest on the basilar membrane.

Question 11

Spiral ganglia

Answer 11

Cell bodies of the sensory neurons

Question 12

How do the auditory ossicles function in hearing?

Answer 12

They amplify and transmit the vibratory motion of the eardrum to the oval window, which in turn sets the fluids of the internal ear into motion.

Question 13

5. Trace the path of a sound wave from outside the ear to stimulation of the vestibulocochlear nerve.

Answer 13

1. Tympanic membrane
2. M-I-S
3. Oval window
4. Perilymph in scala vestibuli
5. vibrates the basilar membrane
6. Movement of the basilar membrane/shifting of tectorial plate causes hair cells to depolarize and hyperpolarize.

Question 14

6. Describe the auditory pathway from stimulation of cranial nerve VIII to the brain.

Answer 14

1. Bending of hairs in the organ of corti causes the release of glutamate which generates nerve impulses in the sensory neurons that innervate the hair cells. 1st order
2. Pass cell bodies in spiral ganglion of cochlear nerve
3. Axons (cochlear branch cranial VIII)
4. Synapse with cochlear nuclei in medulla oblongata
5. Some axons –> lateral lemniscus –> inferior colliculus
6. Some axons –> superior olivary nucleus in pons (localize sound and activate tensor/stapedius muscle)
7. From inferior colliculus –> medial geniculate nucleus/thalamus –> temporal lobe/primary auditory cortex.

Question 15

Attenuation reflex

Answer 15

Tensor tympani and stapedius muscle contract reflexively to limit the ossicles vibration and minimize damage.

Hook to malleus and stapes. Reduce vibration from/to tympanic membrane/oval window.

Question 16

Auditory tube

Answer 16

Equalizes pressure in middle ear.

Question 17

Transduction for hearing

Answer 17

Air waves –> mechanical vibrations, then fluid waves, chemical signals and action potentials.

Question 18

Differences in the fibers of the basilar membrane

Answer 18

Base = short, stiff fibers
Apex = long, floppy fibers

Question 19

What are the sensory receptors for hearing?

Answer 19

Hair cells in spiral organ

Question 20

Five taste sensations

Answer 20

Sweet, salty, sour, bitter, umami