Lecture 20

Question 1

What is the basic pathway followed by sound waves from when they enter the external ear to when they are sensed by the internal ear?

Answer 1

1. The sound will strike the tympanic membrane causing it to vibrate
2. The vibration is then passed through the bones of the middle ear
3. Travels from the stapes to the oval window setting up a fluid wave
4. The fluid wave then travels through the cochlear duct bending the hairs of corti
5. The action potential set up in the cochlear division of the vestibulo-cochlear nerve travels to the CNS
6. The round window then allows for vibration

Question 2

How does the structure of the inner ear change the incoming sound waves to action potential in CNVII?

Answer 2

1. Endolymph contains a very high concentration of potassium
2. The sensory organ for sound is the organ of Corti, which is found on the top of the basilar membrane within the basilar duct (contains hair cells- with stereocilia attached to them)
3. Deflection of the stereocilium towards the tallest stereocilium allow potassium to be able to flow down it’s concentration gradient

Question 3

Sound of increasing amplitude leads to sterocilia bending __(A)____ the source and ___(B)___ the number of AP’s fired.

Answer 3

A) towards

B) increases

Question 4

Sound of varing frequency causes different parts of the basilar membrane to vibrate. Vibration at the oval and round windows will occur in response to ___(A)___ frequencies, whereas deflection occurs further towards the apex at _____(B)_______ frequencies.

Answer 4

A) higher

B) lower

Question 5

Briefly describe the neural pathway of sound:

Answer 5

1. Afferent signals travel along the vestibulo-cochlear nerve
2. Terminate in the cochlear nuclei
3. Travels from the cochlear nuclei to the thalamus to the auditory cortex of the brain
4. Auditory cortex is tono-tropic (“frequency map”)

Question 6

Name the tastes that are detected by type one taste buds:

Answer 6

Salty

Question 7

Name the tastes that are detected by type two taste buds:

Answer 7

sweet, umami, bitter

Question 8

Name the tastes that are detected by type three taste buds:

Answer 8

sour

Question 9

What are the three types of cranial nerves involved in the afferent taste pathways?

Answer 9

VII, IX and X

Question 10

What is the main function of the vomeronasal organ?

Answer 10

Main function of the vomeronasal organ is in the detection of pheromones.