Special Senses Flashcards
(103 cards)
What is sound?
A pressure wave that spreads out from a source, using a medium whose particles vibrate.
What is frequency?
Pitch
The number of vibrations per second in Hertz
What is a typical range of hearing for a young human?
20-20,000Hz
What is loudness?
Intensity
Strength of the vibrations
What is the loudest sound we can hear?
100 trillion times the energy of the quietest sound we can hear.
Use log scale called decibels
What would differ in a 10dB increase in terms of perception and energy?
Perceived as twice as loud
Has 10 times the amount of energy
Why do we have two ears?
So we can localize sounds on a horizontal plane.
Time difference is cue
What is the pinna
External portion of ear
Amplifies, shapes, and filters sound to give directionality
Filters out high frequency sound from behind
Helps distinguish front from back, and up from down (due to shape)
What is the ear canal?
A tube
Sounds at central frequencies are amplified (by about 10dB) in here because of resonance.
What structures make up the outer ear?
Pinna and ear canal
What structures make up the middle ear?
Tympanic membrane Ossicles (malleus, incus, stapes) Eustachian tube Stapedius Muscle Tensor Tympani
What structures make up the inner ear?
Cochlea
Vestibule
Semi-circular canals
Oval window
What amplifies sound?
- The area ratio of tympanic membrane and the oval window causing a 25dB increase in loudness
- The lever action of the ossicles
What embryological structures give rise to the ossicles?
First branchial arch turns into mandible and gives rise to malleus and incus
Second branchial arch gives rise to stapes
What structures are found within the middle ear that help protect from load noises?
Stapedius Reflex- connects to stapes and contracts when ear is exposed to loud sound to protect the cochlea
Tensor Tympani- Large muscle running up eustachian tube joining onto back of malleus. Stop you from blowing out tympanic membrane when coughing and sneezing. Protects from loud sound
What is the eustachian tube?
Cartilage and bone lined in mucosa moving from nasopharynx to middle ear.
Allow air into middle ear to equalize pressure, allowing tympanic membrane to vibrate appropriately
What are conductive hearing loss problems?
Inner ear works fine, but sound is appropriately conducted to the cochlea
Can correct by vibrating the skull
What are some causes of hearing loss in the outer and middle ear?
Ear canal- wax, foreign body, congenital atresia
Tympanic Membrane Perforation
Ossicles- congenital fusion, damage from infection
Middle ear space- fluid instead of air
What structures sit on either end of the ossicles?
Tympanic membrane sits by malleus, and oval window (fenestra ovalis) sits beside the stapes and is much smaller
What is the vestibular apparatus for and what structures are apart of it?
For balance
Utricle & Saccule - linear acceleration
Semi-circular canal- rotatory motion in 3 planes
Contain sensory epithelial
What is the Cochlea and what is it used for?
Forms part of the inner ear, used for converting physical vibrations into electrical impulses
Joined to utricles/saccule, and semi-circular canal
How does sound move from the oval window through the inner ear?
Vibrations passed to oval window -> vestibule -> scala vestibuli -> helicotrema -> back through scala tympani (lower cochlear duct) -> waves terminate at round window
What is found within the Scala Media?
Contains the Organ of Corti (sensory epithelium containing auditory hair cells) Stria Vascularis (regulates electrolyte composition within endolymph so it optimal for hair cell function)
What is contained within the organ of corti?
Tectorial membrane superior
Spiral ganglion
Auditory nerve fibers
Basilar membrane