Hearing And Vestibular Senses

Question 1

Vestibular sense

Answer 1

Ability to both detect rotational and linear acceleration and use this to inform our sense of balance and spatial orientation

Question 2

Describe the initial travel of a sound wave through the ear

Answer 2

• Sound wave reaches the cartilaginous outside auricle to channel sound waves to the external auditory canal
• directs sound waves to tympanic membrane
• membrane vibrates in phase w sound
• ossicles transmit and amplify the vibrations from the tympanic membrane to the inner ear
• the malleus acts on the incus which acts on the stapes (baseplate of which sits on the oval window)

Question 3

How is the middle ear connected to the nasal cavity?

Answer 3

The Eustachian tube, equalizes pressure between the middle ear and the environment

Question 4

The inner ear sits within…

Answer 4

• Bony labyrinth
• Hollow region of temporal bone containing the cochlea, vestibule, and semicircular canals

Question 5

Inside the bony labyrinth…

Answer 5

• Rests a continuous collection of tubes and chambers called the membranous labyrinth
• receptors for sense of equilibrium and hearing

Question 6

Fluids in the membranous labyrinth

Answer 6

Potassium rich endolymph
Suspended within the bony labyrinth by a thin layer of perilymph

Question 7

Describe the parts of the cochlea

Answer 7

Receptors for hearing

Scalae~
- middle: organ of corti actual hearing apparatus, hair cells bathed in endolymph
- other two: perilymph, continuous with oval and round windows of cochlea

Question 8

Sound enters the cochlea…

Answer 8

• through oval window
• causes vibrations in the perilymph
• transmitted to the basilar membrane
• the round window permits perilymph to actually move within the cochlea
• hair cells of organ of corti transduce physical stimulus into an electrical signal which is carried to CNS via auditory nerve

Question 9

Vestibule

Answer 9

• utricle and saccule of bony labyrinth
• sensitive to linear acceleration
• help determine orientation in space
• contain modified hairs covered in otoliths which resist motion
• bend and stimulate underlying hair cells

Question 10

Semicircular canals

Answer 10

• 3
• Sensitive to rotational acceleration
• each ends in a swelling with hair called ampulla
• head rotate, endolymph resist motion and bend underlying hair cells

Question 11

Auditory pathways

Answer 11

• most sound info passes through vestibulocochlear nerve to the brainstem and ascends MGN of thalamus
• nerve fibers project to the auditory cortex in temp lobe
• some info also sent to sup olive which localizes sound and the inf colliculus involved in startle reflex

Question 12

Hair cells

Answer 12

• long tufts of stereocilia
• vibes reach basilar membrane under organ of corti
• stereocilia sway and cause ion channels to open which cause receptor potential
• some are also directly connected to the immobile tectorial membrane, amplify incoming sound

Question 13

Place theory

Answer 13

High freq vibrate basilar membrane close to oval window
Low freq vibrate basilar membrane away from oval window
Cochlea has tonotopical organization