Hearing and balance

cerumen

ear wax

protects + cleans ear

what is the function of ear wax?

hammer (malleus), anvil (incus), stirrup (stapes)

auditory ossicles

amplify sound: sound moves the hammer which moves the anvil with moves the stirrup with punches the oval window and produces sound waves

what do the auditory ossicles do?

air

What is the middle ear filled with, normally?

1. pinna


2. External acoustic meatus (auditory canal)
3. Tympanic membrane


2. Ossicles amplify the sound waves
3. Oval window
4. Basilar membrane in the spiral organ of Corti
5. Hair cells of the tectorial membrane are bent when the basilar membrane vibrates against it

path of conduction of sound waves

temporal bone

in what bone are the cochlea, vestibule, and semicircular canals located?

hearing: inside spiral organ bathed in endolymph, resonance of basilar membrane and stimulation of hair cells to pitch of sound, hair cells detect vibrations in tectorial membrane

what stimulus is the cochlea designed to sense? How?

static equilibrium, linear acceleration

what stimulus is the vestibule designed to sense? How?

dynamic equilibrium, angular acceleration, sensation of gravity

what stimulus are the semicircular canals designed to sense? How?

spiral organ/organ of corti

part of cochlear duct

Hair cells (and support cells) sit on basilar membrane

Tectorial membrane sits on top of hair cells

As sound waves move through vestibuli they oscillate the tectorial and basilar membranes impacting the hair cell

basilar membrane

Hair cells of the tectorial membrane are bent when the _____ ____ vibrates against it

hair cells sit on top

found in cochlea

tectorial membrane

found in cochlea

movement detected by hair cells

sits on top of hair cells

3 outer rows of hair cells

1 of 2 types of hair cells in spiral organ

MOTOR

DANCE

served by motor Efferent fibers

possibly modulate movement of tectorial membrane

protect from overstimulation

1 inner row of hair cells

1 of 2 types of hair cells in spiral organ

SENSORY

link to sensory Afferent fibers

primary output of nerve impulse

oval window

on the cochlea

entry for sound E

energy from the “stirrup” hitting it

round window

found on cochlea

exit for sound E

vestibule

**sound dissipates**

with aging: becomes more stiff

inside the cochlear duct

Where is perilymph found?

Inside the semicircular canals and the vestibule

Where is endolymph found?

vestibulocochlear nerve (VIII)

cranial nerve for hearing and balance

vestibular and cochlear branch

branches of the vestibulocochlear nerve

nystagmus

vision condition in which the eyes make repetitive, uncontrolled movements because the brain and the eye aren’t on the same page and that affects the way our brains interpret movement signals from the eye

your middle ear can feel that you are moving, but if your eyes are focused on something unmoving, your balance and your sight don’t match up, and your brain can’t make sense of the signals, triggering a nauseous response

why do people get motion sickness?

pitch is set by frequency of sound waves, volume is set by intensity or amplitude of a sound wave

What determines a sound's pitch? volume?

pitch is determined by the location of the cells stimulated in the cortex (sympathetic vibrations), volume is determined by the frequency of the arriving impulses

longer cells=sense lower pitched sounds

How are pitch and volume "sensed" by the cochlea?

frequency

sets pitch (high ______ = high pitch)

measured in Hz (cycles per second)

“wavelength”

wavelength

determines frequency of sound (which sets the pitch)

measured in HZ

amplitude

“intensity” of a sound wave

determines volume (loudness)

measured on logarithmic scale decibel (dB)

the location of the hair cells in the spiral organ that vibrate from a sound wave determines the pitch (longer cells=lower pitch)

How do we perceive pitch?

shorter hair cells

Where are high frequency sounds sensed in the cochlea?

long hair cells

Where are low frequency sounds sensed in the cochlea?

death of hair cells, defect with inner ear

Why does our sense of hearing decline as we age (Presbycusis)?

semicircular canals, vestibule

component parts of vestibular apparatus

hair cells + supporting tissue contain the otoliths which is the ear stone that slides over gel and bend hair cells as head moves

what’s the macula and what’s inside it?

otoliths

ear stones

made of calcium and carbonate

slide over gel and bend hair cells as head is moved

utricle

one of otolith organs that senses forward tilt and acceleration

ex: Feeling when you slam on breaks

saccule

otolith organ senses vertical forces like gravity

ex: feeling when you drop in elevator

semicircular canals

Where are the cristae ampullares?

cupula

gelatinous structure in the crista ampullaris that moves when hair cells around is move from changes in velocity of rotational movement

angular acceleration (gyroscope)

What type of motion is sensed by the semicircular canals?

deafness

hearing loss → no sound

conduction deafness

sounds cannot get through the outer and middle ear

sensorineural deafness

hearing loss as the result of damage to the inner ear

central deafness

hearing loss from damage to the cochlear nuclei or the central pathways that relay auditory information to the auditory cortex

tinnitus

the perception of sound that does not have an external source, so other people cannot hear it

ex: ringing, humming, buzzing in your ear

Meniere’s syndrome

a disorder caused by build of fluid in the chambers in the inner ear

symptoms: vertigo, nausea, vomiting, loss of hearing, ringing in the ears, headache, loss of balance, and sweating

mom