Nervous System Part 2 Flashcards
(page 8)
label parts a and b of the labyrinth.
A: semi circular canals
B: vesibule
(page 8)
label membrane sacks found inside part a and b shown at 1 and 2.
1: ampullae (three total)
2: saccule, utricle
(page 8)
what tiny organ is found within structure one? what term is used to describe its role in maintaining balance for the body?
each ampullae contains the crista ampularis which is responsible for dynamic equilibrium.
what tiny organ is found within the two structures? what term is used to describe its role in maintaining balance for the body?
the saccule and utricle both contain the macculae which is responsible for static equilibrium.
define the terms dynamic equilibrium and static equilibrium.
dynamic equilibrium (by the crista ampularis) informs the brain of rotational movements. static equilibrium (by the macculae) informs the brain of changes in the head position (head tilt) plus horozontal and vertical movements of the body (linear movements) which includes changes in speed.
when talking about balance perception, the term vestibular apparatus is used. what does this mean?
the vestibular apparatus is the five organs used for balance perception- two macculae and three crista ampularis.
in the labyrinth image on (page 8) label parts c and 3 and name the organ that is found inside 3.
c is the cochlea and 3 is the cochlear duct and inside three is the organ of corti.
the macculae, organ of corti, and crista ampularis are all nearly identical in structure. what do they all have in common? which of the three has something unique in its structure and why?
all contain hair cells and neurons with stereocilia that produce action potentials. all have a bottom layer of epithelia in which the hair cells are sitting in a gel like roof that the stereocilia are imbedded in. the macullae, however, has teeny calcium crystals in the cell like membrane “roof” called otolits that allow the macculae to respond to the pull of gravity- to literally flop backward or forward, left or right, so that the changes in head position and changes in linear movements can be accuaratley detected.
(page 9)
as sound waves enter the ear, vibrations of several structures lead to fluid vibrations in the cochlea. list the sequence of structures ending with the structure which begins the fluid vibrations.
sound waves (air vibrations) that enter the external auditory canal start vibrations in the tempantic membrane which then passes the vibrations > malleous > incus > stapes > oval window (of cochlea). the mallous, incus and stapes are tiny bones known as the ear ossicles.
the process in which sound waves are directed to the cochlea is called sound wave conduction. this process includes pressure amplification of sound waves. what does this mean.
because air vibrations are being turned into fluid vibrations the energy of the air vibration needs to be increased. this is because it takes more effort to move fluid than air.
how does pressure amplification of sound waves take place?
the energy of the sound (air vibrations) is increased by transferring the vibrations of the tempanic membrane into a much smaller structure, the oval window of the cochlea. the oval window of the cochlea is about 1/20th of the ear drum. which means the energy of the vibration is increased by 20 percent. this increase is necessary to start the fluid vibrations inside the cochlea.
there are three conditions which commonly cause conduction deafness. what is the overall cause of hearing loss in this type of hearing loss? what are the major causes?
the conduction deafness hearing loss occurs when sound vibrations are prevented from reaching the cochlea. the major causes are otitis media, otosclerosis, and a ruptured typantic membrane. the last two are often caused by ottits media but may occur for other reasons.
besides the sound wave conduction, what other important activity are the ear ossicles involved in?
the ear ossicles can reduce the volume of extreme sounds (to avoid damage) by a process called the sound attenuation reflex.
describe how the ear protects itself from loud noises. include what controls this process.
sound attenuation reflex: the trigeminal and facial cranial nerves are both connected to the ear ossicles by teeny muscles. these nerves cause the muscles to contract which pulls on the ossicles and slows their vibrations reducing the ear bones vibrations lowers the volume of the sound being transmitted in to the cochlea.
what are the shortcomings (limits) of the sound attenuation reflex?
the sound attenuation reflex cannot protect against sudden explosive noises OR substained noised of longer than ten minutes. it only protects against slowly building noises, that are brief in length.
(page 11)
name the fluid found in the three ducts or chambers.
vestibular duct = perilymph
cochlear duct = emdolymph
tympanic duct = perilymph
(page 11)
which chamber has fluid vibrations that are started by the stapes at the oval window? how do the fluid vibrations reach the organ of corti and eventually exit cochlea?
the stapes knocks against the oval window- opening in the top chamber, or vestibular duct, which begins perilymph vibrations inside. the fluid vibrations are passed downward as follows: perilymph and vestibular duct > endolymph in cochlear duct (organ of corti location) > perilymph in tympanic duct > exit cochlea through round window of tympanic duct.
(page 11)
label parts a through f
a: basilar membrane
b: outer hair cell
c: stereocilia
d: tectorial membrane
e: cochlear nerve
f: inner hair cell
when the endolymph surrounding the organ or corti vibrates, what happens that allows us to hear sounds?
when the endolymph vibrates, it causes the basilar membrane to vibrate. vibration of the basilar membrane causes the hair cells to dance up and down which bends the stereocilia of the hair cells. this causes the inner hair cells to produce action potentials. these action potentials flow down the cochlear nerve into the brain and the brain hears sound because of them.
what is the cochlear amplifier? how is it related to inner hair cells and outer hair cells?
the cochlear amplifier is made up of three rows of outer hair cells (OHCs). the OHCs do not make the AP’s that are sent to the brain for hearing- only the IHCs do that. instead the OHCs amplify/enhance the performance of the inner hair cells- they help the IHCs select which sounds to pay attention to and allow the IHCs to distinguish between a large number of pitches. certain antibiotics damage the OHCs causing permanent hearing loss- which shows the OHCs importance in the hearing process.
(page 12)
how does the height, or amplitude, of a sound wave affect sound.
the amplitude of the sound wave is what determines sound volume.
(page 12)
what kind of sound is the sound wave marked with?
a short sound wave is a low amplitude wave or a soft (low volume sound).
how do inner hair cells of the organ of corti tell the brain whether a sound is loud of soft?
in response to soft sounds, hair cells fire of a small number of AP’s. (this is called a low frequency of AP’s). in response to loud sounds, hair cells fire off a large number of AP’s. (a high frequency of AP’s).
complete the sentence:
the louder the sound, the _____ the amplitude or _____ of the sound wave.
taller; height.
the brain can tell the difference between a soft versus a loud sound based upon the _____ of AP’s the organ of corti produces.
number (frequency)
(page 13)
how does a low pitch sound differ from a high pitch sound?
a low pitch sound has a small number of waves per second. therefore, a low pitch sound is a low frequency sound wave. a high pitch sound has a large number of waves per second or is a high frequency sound wave.
(page 13)
in the image above, which sound wave is a high pitched sound?
B.
(page 13)
how does the organ of corti tell the brain what the pitch of the sound is?
the specific part of the basilar membrane that vibrates is what tells the brain about the pitch of a sound. this also means that the pitch is determined by how far the sound travels down the basilar membrane.
(page 13)
how does the thickness of the basilar membrane change as you go from the front (the base) to its end (the apex)?
the basilar membrane gets increasingly thinner from start to end. it begins narrow and stiff at the base and thins until it is wide and floppy at its end, the apex.
(page 13)
what types of sounds can vibrate from the beginning (base) of the basilar membrane?
sounds with large numbers of waves per second have maximal vibrations at the base. this means high pitched sounds vibrate at the base. (notice the image says 20,000 hZ at the base- this means 20,000 waves per second). high frequency sound wave = high pitch sound.
what types of sounds can vibrate the end (apex) of the basilar membrane?
sounds with a small number of waves per second (low frequency) or low pitched sounds. (notice that the lowest pitch we can hear is a 20 hZ or 20 waves per second.)
what is a major cause of sensorineural deafness?
the major cause of sensorineural deafness hearing loss is the gradual loss/dissapearence of hair cells that occur with aging. sensorineural deafness: permanent hearing loss caused by damage to any type of neuron in the hearing pathway such as neuron damage in the cochleal (hair cells) cochlear nerve, and the brain stem.
what causes high frequency hearing loss? what is happening in the cocheal?
the innability to hear high pitch sounds occurs as a result of prolonged exposure to loud noises or is often due to a single sudden explosive sound. excessivley loud sounds have air vibrations that are so violent that they tear the stereocilia off of hair cells which causes the hearing loss.
what is the rarest type of sensineural deafness?
hearing loss due to neuron damage in the brain- specificallly damage in the auditory cortex of the temporal lobe.
what is tennitus? what is one theory about this cause?
tennitus is ringing, buzzing or clicking in the ears in the absence of incoming sound of that type. it is a sign of damage and or irritation of inner ear structures often occuring after exposure to excessively loud sounds. one theory is it is caused when damaged hair cells spontaneuously make their own noises which are called otoacoustic emissions. the inner hair cells fire off AP’s into the brain even though they are not being stimulated by sound waves- so they are producing their own noises out of thin air.
controls the skeletal muscles of the face
facial nerve
main nerve used to move the eyeball
ocularmotor
has ophthalmic maxillary and mandibular
trigeminal nerve
allows for hearing and balance
vestibulocochlear
moves the eyeball laterally
abducens
moves the tongue for speech
hypoglossal
main nerve used for taste
facial
allows for vision
optic nerve
moves the eye out and down
trochlear
has important role in the regulation of blood pressure and breathing rate.
glossopharyngeal, vagus
controls mastication muscles
trigeminal
regulated parasympathetic actions of almost all organs
vagus
moves the tongue during swallowing
glossopharyngeal, hypoglossal
has a section that crosses through the middle ear over the ear drum
facial nerve
allows eyes to focus on nearby objects
oculomotor
controls contractions of the trapezius and sternocleidomastoid muscles
accessory