Physiology II: Hearing I

The exernal and middle ear transmit … to the … inner ear → amplification of sound energy

sound waves, fluid filled

Two sensory organs of the inenr ear: …

cochlea, vestibular apparatus

…: receptors sound waves → nerve impulses → hearing

cochlea

…: sense of equilibrium

vestibular apparatus

…: collects sound waves → ear canal, it also shields sound waves from, the rear and distinguishes sound localization

pinna

…: trap fine foreign particles, protective mechanism for tympanic membrane

ear wax and hairs

When you strike a tuning fork it vibrate back and forth, as the arms move forward they … → creates compression, as the arms move backward, they pull away letting the air molecules spread out → creates rarefaction

push nearby air molecules together

The compresses molecules bump into the next layer of molecules they pass the …, the rarefied zones pull the next molecules slightly apart

disturbance forward

… by compressing and rarefying air molecules, these waves carry sound away from the source, allowing you to hear it even at a distance

mechanical sound waves

…: depends on frequency

pitch

…: depends on amplitude

intensity (loudness)

…: depends on overtones

timbre (quality)

…: the faintest sound that is just audible

hearing threshold

…: logarithmic measure of intensity compared to hearing threshold

decibel

the logarithmic scale, compares loudness of … and …

rustle of leaves, rock concert

…: transfers vibrations of tympanic membrane to fluid movement in inner ear

middle ear

…:Vibrates with sound waves from external ear, pressure needs to be equal in external and middle ear

tympanic membrane

…: connects to pharynx, equalizes (atmospheric) pressure in middle ear

eustachian tube

Eustachian tube equalizes pressure by: … (3)

yawning, chewing, swallowing

…: transmit frequency of movement from tympanic membrane to oval window

ossicles

Pressure on the oval window causes waves in the … at frequency of sound waves

inner ear fluid

…: tightening of the tympanic membrane → diminishing transmission to inner ear

reflex of middle ear

…: flexible membrane that relieves pressure inside the cochlea as fluid moves

round window

Three parts of the cochlea: …

scala vestibuli, scala media, scala tympani

…: carries fluid wave from the oval window

scala vestiuli (upper chamber)

…: contains the organ of corti

scala media (cochlear duct. middle chamber)

…: carries fluid wave toward the round window

scala tympani (lower chamber)

Parts of the organ of corti: …

basilar membrane, tectorial membrane, inner hair cells, outer hair cells, stereocilia, supporting cells, auditory nerve fibers

…: vibrates in response to fluid waves, different parts vibrate to different frequencies

basilar membrane

…: gel-like structure that lightly contracts the hair cells stereocilia, helping bend them during vibration

tectorial membrane

…: main sensory cells that convert mechanical vibration into electrical nerve signals

inner hair cells

…: amplify and fine-tune the movement of the basilar membrane, improving hearing sensitivity and frequency discrimination

outer hair cells

…: detect movement, bending opens ion channels, creating an electrical signal

stereocilia

…: provide structural stability and maintain the health of hair cells

supporting hair cells

…: carry the electrical signals from hair cells to the brain for interpretation as sound

auditory nerve fibers

Pathway 1 of sound: vibrations through the scala vestibuli → around helicotrema → through the scala tympani → causing the round window to vibrate → …

dissipates sound energy

Pathway 2 of sound: From scala vestibuli → through basilar membrane → scala tympani → activations of sound receptors → by bending the hairs of hair cells as the organ of corti on top of the … is displaced in relation to the overling tectorial membrane

vibrating basilar membrane

The stereocilia from the hair cells of the basilar membrane contact the overlying tectorial membrane. These hairs are bent when the basilar membrane is deflected in relation to the … this bending of the inner hair cells opens mechanically gated channels, leading to ion movement that results in a receptor potential

stationary tectorial membrane