lecture 10 - special senses Flashcards
visual field
what an eye sees
each visual field is divided in two halves;
nasal (central) half
temporal (peripheral) half
how do the visual fields work?
info from the left half of each visual field goes to teh right side of the brain and vice versa
where does light fall on the retina if it is coming from teh nasal side?
teh temporal side of teh retina
light crosses sides in the retina
NOTE: whatever side light hits the RETINA, the signals goes to the same side of the brain. BUT light crosses in the retina
eg. left eye, light coming from right side (nasal half), light will hit temporal retina (left side of the left eye), it will go to the left side of the brain because it is coming from the right side (nasal side in this case)
NOTE: only fibres from the nasal half of the retina cross in the optic chiasm, not the temporal retina
binocular vision
visual field of two eyes overlap
this is why you can see a lot when you cover one eye
summary of what light goes where in the brain
peripheral (temporal half) stimuli cross at optic chiasm, central (nasal half) stimuli do not
what happens if teh optic chiasm is damaged?
peripheral vision is impaired or lost
this is bc peripheral vision crosses the optic chiasm, and central vision does not
stapedius muscle
restrict vibrations of stapes to decrease hearing sensitivity
CN VII
tensor tympani muscle
attaches to malleus and stiffens eardrum
- CN V
outer bony labyrinth is filled with:
parts of this:
perilymph
semicircular canals, vestibule, scala vestibuli and tympani (cochlea)
inner membranous labyrinth is filled with:
parts of this:
endolymph (high K conc)
semicircular ducts, cochlear duct
vestibular membrane
separated cochlear duct from scala vestibuli (above spiral organ)
basilar membrane
separates cochlear duct from scala tympani (below spinal organ)
spiral organ
rests on basilar membrane and contains hearing receptors
tectorial membrane
projects overtop of spiral organ
hair cells of the spiral organ
stereocilia
inner hair cells
hearing receptors (site of transduction)
synapse with first order neurons
outer hair cells
increase sensitivity of inner hair cells and synapse wiht motor neurons
sound waves
alternating regions of high/low pressure traveling in the same direction thru one medium
amplitude
determines volume or intensity of sound
frequency
determines pitch
helicotrema
where scala vestibuli and tympani meet
hearing steps (
- auricle directs sound waves to external acoustic meatus
- tympanic membrane vibrates
- vibrations are transmitted thru the ossicles
- stapes makes vestibular window vibrate
- fluid pressure waves develop in the perilymph of scala vestibuli
- pressure waves transmitted from scala vestibuli to tympani thru helicotrema and to the cochlear window
- pressures waves push vestibular membrane back and forth creating pressure waves in the endolymph of the cochlear duct
- pressure waves cause basilar membrane to vibrate which causes movement of stereocilia which causes a receptor potential
tip link protein
connect mechanically gates channel in stereocilium to the tip of the taller one next to it
resting hair cell has: (7)
straight stereocilia
- tip link in resting position
- partially opened cation channles
- a bit of K entering
- weak depolarizing potential
- small influx of Ca
- small number of NTs released
- low freq nerve impulse
strongly depolarized hair cell has: (7)
- bent stereocilia (short bending to tall)
- tip link stretched
- fully opened cation channels
- lots of K entering
- strong depolarizing potential
- large influx of Ca
- large number of NTs
- lots of nerve impulses to first order neurons
hyperpolarized hair cells have (7)
- bent stereocilia (tallest bent to shortest)
- tip link proteins are stacked
- fully closed cation channels
- no K entering
- hyperpolarizing potential
- small influx of Ca
- few NTs released
- very few nerve impulses to first order neurons
auditory pathway
cochlear branch of CN8
- cochlear nuclei in medulla
- some axons go to pons
- axons go to inferior colliculi
- axons go to thalamus
- then to primary auditory cortex
- then to auditory association area
which structures of the ear contain endolymph (3)
saccule, utricle, cochlear duct
vestibular apparatus structures (3)
utricle, saccule, semicircular ducts
receptors in vestibular apparatus (2)
macula receptors
crista receptors
macula receptors location
in utricle and saccule
crista receptors lcoation
within ampulla of semicircular canals
macula (ear) receptors detect:
position of the body/head relative to gravity (like head tilt) and linear accel/decel
crista receptors detectL
position of body/head during rotational accel/decel
otolithic organs
utricle and saccule
also called sacs of membranous labyrinth
macula cell types
hair cells with stereocilia
- supporting cells that secrete otolithic membrane
otolithic membrane
covered hair cells of the macula
- contains crystals called otoliths that move when the head moves
kinocilium
tallest hair among the stereocilia from each hair cell
hair bundle
stereocilia + kinocilium
steps on how head movement affects the macula (
- head movement
- otolithic membrane movement
- stereocilia bend
- depolarization of hair cells
- NT release to CN7
maculae in the utricle and saccule are:
perpendicular to each other
utricle - horizontain movement
saccule - verticle
position of the semicircular ducts permitsL
detection of rotational accel/.decel
ampulla
dilated portion of each semicircular duct
contain crista
crista cell types
hair cells
supporting cells
- supporting cells secrete cupula
cupula
gelatinous material covering crista
how does the crista apparatus work
as the head rotated, the cupula (covering the crista) is dragged through the endolymph and bent in the opposite directions
this delay of movement causes the hair cells to bend, which triggers depolarization and NTs released to CN7
equilibrium pathway
CN 8 to vestibular nuclei in medulla and pons
- some axons go to cerebellum thru peduncles
- from medulla/cerebellum to cranial nerves that control the head eyes and neck
- info sent to motor areas to adjust balance and posture
