physiology-sense organs (hearing and equilibrium)

the response to vibrating air molecules

hearing

the sense of body orientation, motion, and balance

equilibrium

any audible vibration of molecules and is produced via vibration; air molecule collisions occur until it hits the eardrum

sound

what does the sensation of sound depend on

pitch and loudness

sense of whether a sound is high or low and is determined by the frequency the sound source, eardrum, or other parts of the ear vibrate

pitch

one movement of vibrating back and forth

cycle

number of cycles per second (Hz)

frequency

what is the frequency that children or people with sensory ears can hear

20-20000 Hz

what is the frequency that normal speech is usually at

1500-5000 Hz

what frequencies is typically seen to be lost with age

250-2050 Hz

the perception of sound energy, intensity, or amplitude of vibration; expressed in decibels (dB)

loudness

how much compression the air molecules experience

amplitude

what is loudness expressed in and what is the threshold of human hearing

decibels (dB) - 0 dB

why can amplitude be damaging

every 10 dB increase is a 10x greater intensity

what are the three sections of the ear

outer, middle, and inner

what are the sections of the outer ear

auricle and auditory canal

directs air vibrations down the external auditory meatus

auricle

lined with hairs and ceremonious glands that produce cerumen for protection and waterproofing

auditory canal

the tympanic cavity that contains oval and round windows to separate it from the inner ear

middle ear

the border between the external and middle ear and sound waves cause it to vibrate

tympanic membrane

part of the middle ear that opens into nasopharynx, equalizes pressure, drains middle ear, and is a passage for air

auditory tube

what does the middle ear contain the smallest of in the body

3 bones and 2 muscles

what are the three auditory ossicles of the middle ear

malleus, incus, and stapes

connects the tympanic membrane to the inner ear and transmits vibrations from the eardrum to the oval window

auditory ossicles

what are the two muscles of the inner ear

tensor tympani and stapedius

what part of the ear contains a bony and membranous labyrinth and have both hearing and equilibrium portions

inner ear

where do the labyrinths of the inner ear begin

vestibule

surrounds the inner structure

bony labyrinth

lines the bony structure

membranous labyrinth

is the cushion between the bony and membranous labyrinths

perilymph

what is the fluid within the membranous labyrinth

endolymph

what is the organ of hearing and contains three fluid-filled chambers that are separated by membranes

cochlea

superior chamber of the cochlea that begins near the oval window and spirals towards the apex

scala vestibuli

inferior chamber of the cochlea that spirals down to the base and ends at the round window

scala tympani

separated from the other chambers of the cochlea by the vestibular and basilar membranes and is filled with endolymph

scala media/ cochlear duct

grouping of sensory and supporting cells in cochlear duct that is responsible for converting vibrations into nerve impulses

spiral/acoustic organ

sensory cells with hair like projections at apical ends called stereocilia; is intervated by afferent fibers that form cochlear nerve within the basilar region that are covered by synaptic terminals of sensory neurons

hair cells

what is the middle ear responsible for physiology wise

transferring the vibrations from the tympanic membrane to the ossicles, creating a force on the oval window that overcomes the inertia of the fluid within the inner ear

how can the middle ear help lessen the transfer of energy to the inner ear at times

tympanic reflex of the lever system of the ossicles

what is the tympanic reflex

in response to loud noise, the tensor tympani pulls TM inward to tense it while the steps reduces the motion of the stapes; result is a muffled transfer of vibrations to oval window

what is the first step in the stimulation of the cochlear hair cells

sound occurs causing the TM to push ossicles inward

what occurs after TM pushes ossicles inward

stapes pushes on perilymph in scala vestibuli snd since fluid cannot be compressed it moves away and increases the pressure in the scala vestibuli

what occurs after an increase in the pressure of the scala vestibuli

pressure pushes vestibular membrane down against the endolymph in the cochlear duct

what happens after the pressure is pushed against the endolymph in the cochlear duct

endolymph increased pressure on basilar membrane to push on the perilymph in the scala tympani

what occurs after the perilymph is pushed down on the scala tympani

round window bulges outward to relieve pressure

what has a high concentration of potassium and an electrical potential of +80 mV

endolymph surrounding the hair cells

what is the charge inside the hair cell

-40mV

what gates the ion channel at the very tip of the stereocilia

transmembrane protein

filament that acts as a spring and connect stereocilia together

tip link

how does depolarization begin within the hair cells of the spiral organ

when basilar membrane gets pushed up, the stereocilia are forced into the tectorial membrane and causes them to bend which opens the ion channels

how is loudness perceived by the cochlea because it causes variations in intensity of the vibrations

vigorous vibrations excite more inner hair cells over a larger area which triggers higher frequency of action potentials, which is perceived as a louder sound

how is pitch/ frequency encoded

depends on which part of the basilar membrane vibrates

to interpret signals as high pitched, what portion of the basilar membrane vibrates

basal end where it is narrow and stiff

to interpret signals as low pitched, what portion of the basilar membrane vibrates

distal end where it is 5 times wider and more flexible

where do the sensory nerve fibers of the ear begin

base of hair cells

whee are the somas of the hear located

spiral ganglion

where do the axons lead to before joining the vestibular nerve to make CN VIII

cochlear nerve

where do the first order neurons of the auditory projection from both sides synapse

cochlear nuclei in pons

from the cochlear nuclei, where do the second order neurons ascend to

superior olivary nucleus of the pons or the inferior colliculi of the midbrain

where do the third order neurons lead from

inferior colliculi to thalamus

where do the fourth order neurons go to from the thalamus

primary auditory pathway in temporal lobe

for the second order neuron, what is the superior olivary nucleus responsible for

binaural hearing to compare sounds from both sides to identify direction and sending motor fibers back to cochlea for cochlear tuning

for the second order neurons, what is the inferior colliculus responsible for

helping locate the origin of sound, process fluctuations in pitch, produce startle response by turning of head to loud sounds

why does damage to either auditory cortex not cause unilateral deafness

extensive decussation of the pathway

perception of head orientation when body is stationary

static equilibrium

perception of motion or acceleration and is split into linear and angular acceleration

dynamic equilibrium

change of velocity in straight line

linear acceleration

change in rate of rotation

angular acceleration

what makes up the receptors for equilibrium

vestibular apparatus with 3 semicircular canals and 2 chambers/ otolith organs

responsible for detecting angular acceleration

semicircular canals

responsible for detecting static equilibrium and linear acceleration

saccule and utricle

a patch of hair and supporting cells within the saccule

macula sacculi

patch of hair and supporting cells within the utricle

macula utriculi

macula that lies vertically

macula sacculi

macula that lies nearly horizontally

macula utriculi

what resides within the macula of the utricle and saccule

hair cells, otolithic membrane, and otoliths

gelatinous material where the tips of stereocilia and kinocilium are embedded

otolithic membrane

calcium- carbonate granules embedded in membrane that add weight and intertia to the membrane

otoliths

how is static equilibrium detected

when head is tilted, the weight of the membrane bends the stereocilia to cause stimulation to bilateral ear and the brain compares to eyes, stretch receptors, and each ear

how is dynamic equilibrium detected

otoliths lag behind, which bends the stereocilia

what detects horizontal acceleration and decelleration

utriculi

what detects vertical acceleration and deceleration

sacculi

what are the three semicircular ducts within the osseous semicircular canals of the temporal bone

anterior, posterior, and lateral/horizontal

the dilated end that each semicircular duct opens up into the utricle at

ampulla

what is found within the ampulla of the semicircular canals

crista ampullaris, cupula, endolymph

mound of hair cells and supporting cells

crista ampullaris

hair cells with stereocilia and kinocilium embedded in gelatinous cap

cupula

how is movement detected in the semicircular ducts/canals

ducts rotate with head but endolymph lags behind, so it pushes the cupula to bend the stereocilia and stimulate the hair cells to cause an AP

where do the hair cells from macula sacculi, macula utriculi, and semicircular ducts synapse at

the base with sensory fibers of vestibular nerve

after synapsing with sensory fibers of vestibular nerve, where does the equilibrium pathway go

vestibular nuclei on each side of pons and medulla; communication between sides here

where is communication between both sides of the equilibrium pathways as well as the position and movement processed

vestibular nuclei on sides of pons and medulla

where are the equilibrium projection pathways relayed to after the information is processed

cerebellum, reticular formation, spinal cord, thalamus, and nuclei of oculomotor, trochlear, and abducens nerves

in terms of equilibrium, what is the purpose of the reticular formation

determines how and where increased blood flow should be sent and postural control

in terms of equilibrium, what is the purpose of the spinal cord

postural reflexes (vestibulospinal reflex) to maintain unconscious balance by activating mainly extensers

in terms of equilibrium, what is the purpose of the cerebellum

motor coordination to make adjustments

in terms of equilibrium, what is the purpose of the thalamus

relay system to be consciously aware of where we are in space

in terms of equilibrium, what is the purpose of sending info to the three cranial nerves

adjust for eye movement in regards to head motion (vestibular ocular reflex)