Ear 2 Flashcards
Describe how sound waves are formed
results from the alternate compression and decompression of air molecules - originate from a vibrating object
Frequency of vibration is directly related to …
pitch - the greater the vibration, the higher the pitch
the larger the intensity of the vibration, the …
louder the sound - measured in decibels (dB)
Describe the passage of sound waves into the ear
sound waves are directed by the pinna into the external auditory canal, they strike the tympanic membrane and the alternate compression and decompression of the air causes it to vibrate
the distance the sound wave moves, which is v small, depends on …
the intensity and frequency of the sound waves
The central area of the tympanic membrane is connected to the …
malleus and so this too also vibrates
Describe what happens to this vibration
transmitted to the incus and then the stapes, then as the stapes moves back and forth it pushes the oval window in and out - the oval window vigorously vibrates because the ossicles efficiently transmit the small vibrations spread over a large s.a. (ear drum) into larger vibrations of a smaller surface (oval window)
Describe the the pressure waves created
waves of pressure are created within the perilymph and the endolymph of the cochlea, pressure waves are transmitted eventually to the round window, causing it to bulge outward into the middle ear
Describe the pressure waves in the endolymph
causes the hair cells within the cochlea to move, the hairs convert the mechanical force into electrical signals or nerve impulses - these are then transmitted to the auditory cortex within the temporal lobe of the brain via the cochlear branch of the vestibulocochlear (CN VIII) nerve
Describe the role of the inner ear in equilibrium/balance
the inner ear aids the brain in determining body position and motion, organs involved in equilibrium = vestibular apparatus - includes the semicircular ducts within the the semicircular canals, the ducts lie at right angels allowing the brain to detect rotational acceleration or deceleration
Describe the role of the ampulla and the role of the fluid in equilibrium
ampulla - dilated portion of each duct contains hair cells so when you move your head, the semicircular ducts and hair cells move with it, endolymph within ampulla lags behind, as the moving hair cells drag along the stationary endolymph, the hair bundles bend - leads to nerve impulses passing along vestibular branch of CN VIII nerve to the major integrating centres for equilibrium
Name the major integrating centres for equilibrium
medulla oblongata and pons and the cerebellum
input here is also received from the eyes and especially proprioceptors in the neck muscles that indicate the position of the head
