4 senses Flashcards
why are the senses important
adaptive significance
adaptation
ie/ neurons becoming less responsive over time
for example, a clock ticking in the background slowly goes away
pinna
external ear or external auditory meatus
captures, focuses and filters sound
they are directional - ears point in a specific direction which aids in localization - figuring out where the sound is coming from
highly mobile in some species
performs early sound processing - pattern of ridges inside act as a spectral filter - increasing and decreasing certain sound frequencies
directs sound waves into ears
guides them into ear canal - leading to middle ear
act as radiators - heavily vascular in some species
meatus
hole from outside to inside
middle ear
tympanum and ossicles
concentrates sound energy
breeding ground for bacteria, pressure is painful, subject to infection
tympanum
eardrum
membrane that seals the end of the ear canal + ossicles
vibrates when struck by sound waves from ear canal - converts sound energy into a form of kinetic energy
when ruptured hearing is impaired
ossicles
tiny bones - chain of them
smallest bones in your body
three of them
concentrate and amplify vibrations focusing pressure on small oval window
amplification is important for converting vibration in air into movements of fluid in the middle ear
what are the 3 ossicles
malleus (hammer), incus (anvil) and the stapes (stirrup)
form an articulated chain (leading from back of ear to cochlea (inner ear)) - mechanically coupling the vibrating tympanum to inner ear (oval window)
for the tymphanum to vibrate, air pressure must be equal on both sides - middle ear contains eustachian tube
if middle ear is tighter than ear is tighter than ear drum, sound waves can not move as freely
eustachian tube
in middle ear
localizes pressure
leads away to the oral- nasal cavity - this is how ear infections get in
connects to let air in and out
middle ear muscles
tensor tympani
stapedius
attach to the end of ossicles
contraction of the muscles alters the ability of the ossicles to move in response to a vibrating tympanum
has a modulating movement of the ossicles , reducing the amount of response to sounds
makes the bones stiffer and less sinsitive
activate just before we produce a self made sound ie/ speech, cough - hence why we do not think our own sounds are crazy loud
tensor tympani
is a tiny muscle connected to the malleus, which is the ossicle attached to the tympanum (makes this tight)
sound waves strike here and cause it to vibrate at the same frequency as the sound.
stapedius
connects the stapes to the floor of the middle ear
modulation of sound
occurs within 200 msec of a loud noise
happens with our own voice
oval window
where the stapes connects to the cochlea
sound
vibrational energy that in a series of compressions
decibel
measure of sound frequency perceived as loudness
perception of amplitude
perceived as a local increase or increase in air pressure
plotted as a sine wave
sound emitters
produce successive compressions are rarefactions in air - think of a loudspeaker cone
frequency
time from peak to peak
pitch Hz or cycles/sec
amplitude
peak height
loudness
db is relative
volume, how loud is the sound (strength)
intensity force sound exerts per unit area
harmonics
are multiples of the fundamental frequency of an emitter
fundamental frequency
predominant frequency of an auditory tone
timbre
is the unique “signature” sound of an emitter, comprised of the fundamental frequencies plus harmonics (or overtones)
character of the sound of an instruments
ie/ we know the sound of different instruments like piano/guitar (knowing they sound different)
doppler shift
occurs if the emitter is in motion
velocity (ie/ how an ambulance sounds far vs. away is added to the rarefraction-compression cycle to change
used by many species, especially bats
resonance
intensity of a vibration
pure tone
a tone with a singer frequency of vibration (frequency and amplitude)
transduction
converting from one form of energy to another
the inner ear
the organ that actually encodes the sound of elements
called a transducer
only the size of a pea
cochlea
fluid filled
converting sound waves from the world into something we can understand (neural activity)
fluids that fill is are not compressible
vibrations transmitted from the tympanum are communicated to the endolymph via the action of the stapes against the oval window
what are the gel fluids that fill the cochlear tubes
endolymph and perilymph
oval window
connection point of ossicles (stapes) to the cochlea
the fluid in the cochlea is not compressible, what does this cause?
there is movement (waves) produced in the endolymph - this propagates through the length of the cochlea
round window
bulges to accommodate the pressure that comes from the compressed fluid
lets energy out of the cochlea
organ of corti
transduces sound waves into neural energy
receptor system
the most important part of the cochlea for hearing
converts vibration from sound into neural activity
consists of auditory sensory cells (hair cells), elaborate framework of support cells, auditory nerve terminals that transmit neural signals to and from the brain
basiliar membrane and tectorial membrane
waves are created in the fluid of the scala vestibula causing the basilar membrane to ripple
vestibulocochlear nerve
fibers contact the bases of hair cells
some fibers convey sound info to the brain
where is the organ of corti located
in the scala media (middle canal of the 3 parallel
basilar membrane
middle canal
one of the membrane that divides the tubes of the cochlea
base: increased frequency, stiff
apex: decrease frequency
hair cells
rows of specialized receptors
inner hair cells
sterocilia protrude from top of hair cell
closer to central axis
base near basiliar membrane
when stimulated, release glutamate onto auditory nervefibers
stereocilia
tiny bristle
nesstles into hollows of tectorial membrane
- form mechanical bridge between two membranes
- forced to bend when sounds cause basiliar membrane to ripple
approximate the tectorial membrane
tectorial membrane
another divider
depolarization of hair cells
even a tiny bend in stereocilia causes a large depolarization of the hair cells
causes the operation of a special type of large and selective ion channels
- allows rush of potassium and calcium in at the base
causes synaptic vesicles to fuse with synaptic membrane and release neurotransmitters to stimulate adjacent nerve fibers
hair cells sway back, stereocilia shuts
the opening and shutting of channels is a way of encoding frequency
depolarization reaching the base of the hair cell causes a calcium channel to open - resulting calcium current provokes transmitter release
the transmitter acts on the auditory nerves leading from the hair cells to the brain
outer hair cells
12000
in 3 rows arranged in parallel
same arrangement of stereocilia
release ACh and are influenced by GABA (inhibatory NT)
hair cells ability to switch on and off
allows them to track the rapid oscillation of the basiliar membrane
hair cells are sensitive
how does the organ of corti work?
- ossicles transmit vibrations to the fluid of the cochlea, setting up traveling waves
- waves cause the basilar membrane to ripple - like the shaking of a carpet
- hair cells have their bases in the basilar membrane, and their stereocilia inserted into the tectorial membrane above
- for any frequency, amplitude of the traveling wave is exaggerated at one particular location of the basilar membrane, due to a prcess akin to resonance
energy is put into the base of the basiliar membrane which is at the stapes which vibrates the round window to go into the membrane
high frequency and smaller response at base
low frequency and heightened response in apex
IHC - afferent
leads to brain
carries info that we perceive as sound
activated by glutamate from the IHS
convey APs to the brain that provide perception of sound info
95 percent of fibers leading to brain
IHC - efferent
from brain to IHC
serve a modulatory function (influences how hair cells are) by inhibiting the IHC - afferent fibres. ACh
allow brain to control responsiveness of IHC’s
OHC - afferent
from OHC to brain
small diameter fibres using ACh
convey info about activity/mechanical state of basilar membrane (moment to moment state)
not thought to be involved in conscious perception of sound
OHC - efferent
from brain to OHC
using GABA, alter the responsiveness of OHC
tuning to make sharper, amplified
can change their length - can modify the stiffness of the regions of the basilar membrane - resulting in sharper tuning and amplification
what does movement of basilar membrane do to stereocilia
causes a deformation and benidng
tip link
connects hair cells
tuning
basilar membrane is tuned by virtue of its changing width but not enough to explain discrimination of 2 Hz
Neural tuning
at higher levels, inputs from numerous auditory fibers (combine and go to brain which increases tuning) converge on neural systems that determine (filter) the frequency of received sound
individual neurons in brain respond selectively to particular frequencies and are inhibited by neighbouring frequencies
lateral inhibition
to sharpen own response will surpress the responses to neighbours
sharpens focus on most central frequency
electromechanical tuning
OHC’s can instantaneously change their length - this changes the responsiveness of the basilar membrane
OHC action amplifies basilar membrane response, sharpening tuning
thus, the basilar membrane is active, rather than passive
otoacoustic emissions
the active nature of the cochlea causes it to emit clicks under certain conditions (just as a microphone can act as a speaker under some conditions)
20 db
evokes otoacoustic emissions
provoked by presented sounds
useful for testing hearing in infants, effects of drugs on hearing, experiments on basic cochlear mechanisms
spontaneous otoacoustic emissions
people that have a good sense of hearing
fair chance that you cochlea are producing spontaneous clicks, but you can not hear them
associated with especially sensitive hearing
females make more
more common in right here thereform left hemisphere (asymmetry)
left hemisphere
specialized for language and connected to right cochlea
major centers in higher brain structures for hearing (in order)
cochlear nuclei
superior olivary complex
inferior colliculus
medial geniculate
auditory cortex
tonotopic arrangement
map of frequencies of a specific location
orderly map
from low to high frequency
precision allows for sharper tuning - differentiating between sounds
auditory neurons are excited by some frequencies and inhibited by others
cochlear nuclei
brainstem
first receiving center in brain - some initial processing
low level integration, tuning and projection to other brain areas
where auditory nerve fibers terminate
receive input from auditory hair cells
output projects to superior olivary complex
superior olivary complex
located in brainstem
receives and integrates inputs from both cochlea
basis of binaural (stereo) hearing - first part of brain that does this
localizes sound by comparing the two ears
passes info to inferior colliculus
inferior colliculus
midbrain
tuning
spatial localization (where sound came from) for some species
primary auditory centers of midbrain
output goes to medial geniculate
medial geniculate
part of the thalamus
outputs extend to many auditory cortical areas
projects to the auditory cortex
auditory cortex
superior temporal cortex (primary auditory area)
integrates non-auditory info with sound
conscious perception of sound
pitch discrimination
we can typically hear sounds for 20 Hz to 20,000Hz
subjective, frequency (physical property of sound) is absolute
place theory
volley theory
place theory
that perceived pitch corresponds to the location on the basilar membrane that is most strongly activated
how it vibrates at certain spots, location of activated hair cells
example of labeled lines each neuron fires in response to its faveourite frequency
treble
increased frequency
base
bass
decreased frequency
apex
volley theory
that pitch is a function of the rate of firing in auditory fibres
500hz= 500AP bending corresponds to the amount of APs
infrasound
less that 20Hz (elephants and whales)
ultrasounds
more than 20,000 Hz (bats and porpoises)
sound localization
evolutionary significance
binaural (2 ear) cues are the best and most obvious
intensity difference
how loud the sound is
for a sound off the midline, one ear is closer than the other to the source
this results in differences in the amplitude of sound received by the two ears (comparison between them)
noise level will vary between ears - helps us localize sound
head shadow
the head blocks sound from getting to the more distant ear, exaggerating the intensity difference
difference more pronounced at higher frequency
time of arrival
when a sound is produced the initial sound waves arrive later at the more distant ear - arrive at one ear before the other
one ear a little closer to the source
the difference in arrival time at the two ears is directly related to the angle of the sound source (but could be in front of or behind the head, in the absence of other cues)
phase differences
related to time of arrival (peaks and troughs)
for an ongoing sound, the peaks and troughs of the sound wave (compressions and rarefactions) have to go farther to hit the more distant ear, and thus arrive a little later (out of phase)
the auditory system can compare the degree of phase discrepancy for an ongoing sound - the greater the discrepancy, the greater the angle of the sound source
onset disparity
difference between two ears in hearing beginning of the sound
ongoing phase disparity
continuing mismatch in two ears between time of arrival of all peaks and troughs that make up the sound wave
ear meat effects
direction of the pinna discriminates from front to back
some animals can swivel the pinnae to locate the sound source
spectral changes can reveal up-down info
cortical areas
extracting biologically relevant info
recognizing important sounds: footsteps, animal calls, vocals of familiar vs. unfamiliar people
spectral filtering
external ear provides another localization cue - hills and valley
left-right asymmetry
planum temporale: bigger on the left possibly due to left hemisphere speech specializations
many music function of right
some language on right side, and some music on left
amusia
disorder characterized by the inability to discern tunes accurately to sing
abnormal function in the right frontal lobe and impovershed connectivity between frontal and temporal cortex
can’t access pitch info
what are the three types of deafness
conduction
sensorineural
central
deafness
can prevent sound waves from reaching cochlea, trouble converting sound waves to APs and dysfunction of brain regions that process sound
hearing loss so profound that speech cannot be perceived even with the use of hearing aids
conduction deafness
normally a problem with the ossicles
middle ear problem - sound blocks vibrations from reaching inner ear
can have ossicles removed
partially or fully fused with aging
ossicles become fused together and vibrations of the eardrum can no longer by conveyed to the oval window of the cochlea
sensorineural deafness
often cochlear
main sort of hearing loss - hair cells blown over like a bunch of tiny trees
ringing that never goess away
headphones, gunshots , car stereos are especially bad
tinnitus
hair cells fail to convert the basilar membrane ripples into volleys of Aps that inform
most often results of permanent damage of hair cells - can happen because of being exposed toloud sounds or from birth - maybe infection
tinnitus
long term exposure to loud sounds, causing ringing in the ears
central deafness
arising from brain damage
damage to auditory brain structures can affect hearing in various ways
impaired by perception of behaviour relevant sounds
ie/ strokes, tumours, traumatic injury
word deafness
selective trouble with speech sounds despite normal speech and normal hearing for nonverbal sounds
cortical deafness
rare, bilateral lesions of auditory cortex
struggle to recognize all complex sounds (verbal and non verbal)
more complete impairness
hearing loss
moderate to severe sensitive sensitivity to sound
vestibular system
system lies in hollow spaces in the temporal lobe
awareness of motion allowing for planning of future movement and anticipate changes due to the movement of the had
have strong connections to the brain
source of motion sickness - may be an adaptation for dealing with poisoning
sense of balance - product of inner ear that adjoin cochlea
where do vestibular system fibres terminate
in vestibular nuclei while some project to cerrebellum to aid motor programming - outputs project to motor areas of the brain
3 semicircular canals
in vestibular system
each in different planes
work together to track the movement of the body
fluid filled
movement of head in one direction causes fluid to circulate
ampulla
otoliths
receptrs are hair cells - bending produces APs
planes of rotation for the three semicircular canals
pitch - nodding up and down
yaw - shaking head side to side
roll - tilting head left/right
ampulla
buldge, base
hair cells translate fluid movement in neaural signal (action potentials)
cilia embedded here - bending cilia in ampulla signals to the brain that the head has moved. movement of the head creates a flow of fluid that bends the stereocilia
otoliths
overlie the hair cells, and amplify the effect of them
earstone - mass lags slightly when the head moves
react to gravity and inertia
made of calcium carbonate - theory rhat it may be dissolved by alcohol making us feel spinner
saccule and utricle
fluid filled cavity
code the position of head when not moving
bulbs
located in ends of semicircular canals
each have an othilic membrane
motion sickness
experience of nausea because of unnatural passive movement - movement of the body we can not control
too much vestibular stimulation
ie/ passengers in the car are more likely to get it than the driver (not in control)
sensory conflict theory
we feel bad when we receive contradicting sensory messages - especially between visual and vestibular
hypothesis is that stimulation activates a system originally evolved to rid the body of swallowed poison
little evidence, remains a mystery
somatogravic illusion
in conditions of low visability, acceleration may be determined as an upward tilt of the plane
tongue
possesses sensory cells for pain, touch and temperature
taste buds
between papillae in the walls
50-150 taste receptor cells that detect taste
papillae
tiny lumps on the tongue that increase SA of the tongue
taste cells
have microvilli that extend from them into a tiny pore, where they come into contact with
sensitive to tastants
1/5 of basic tastes
life span= 10-14 days - constantly being replaced
anything dissolved in the saliva can get here
fungiform papillae
mushrooms
usually one taste bud each
foliate papillae
sides of the tongue
multiple taste buds
circumvallate papillae
big suckers at the back of the tongue
multiple taste buds
kokumi
only some people have
primary fat taste
what are the five basic tastes
sweet, salty, sour, bitter and umami
which tastes need simple ion channels
salt and sour
salt
simple ion pore tht admits sodium ions from NaCL
cells have sodium channels, they will enter and create a signal
causes a depolarization and release of neurotransmitter
pore is also sensitive to Cl
TRPV1 - secondary salt sense, can also sense heat
sour
derive from acids which release H+ ions
ions block potassium channels on the tastebud cells
acid in foods taste sour - more acidic the food the more sour it tastes
sweet
a type of metabotropic receptor
GPCR - recptor activating 2nd messenger system
T1R2 + T1R3 - combine to make a receptor that detects sweet
bitter
metabotropic type receptor
important biological system - posions
T2R’s
exhibit broadly tuned sensitivity to any bitter substance - evolved as a poison detector family
often signals in the presense of toxins
unami
glutamate receptor
T1R1 + T1R3 dimer (GPCR)
closely related to sweet
meaty, savour flavour
responds to amino acids and glutamate
MSG
where does taste project from
extends from tongue to several brainstem nuclei and then to thalamus, then to gustatory region of the somatosensory cortex
taste is a labeled line system
selectively inactivating taste cells expressing for one taste that does not effect the others
olfaction
odour perceptions
requires stronger stimulation for humans
forms the lining of the nasal cavity
what are the three major cell types in the olfactory system
support cells
basal cells
olfactory receptor cells (main)
odorants
dissolve into the mucousal layer and interact with receptors of the dendritic cilia
GPCRS is the second messenger system that responds to odours
olfactory neurons go into
olfactory bulb and then to glomerulus with tunes and sharpens and then organizes them into a tonotropic map
mitral cells
convey olfactory info to the brain
extends from glomerulus
targets for olfactions
does not go through thalamus
targets are hypothalamus, amygdala and prepyriform cortex
regeneration in olfaction
olfactory cells are constantly being replaced
adaption to chemical attack and viruses
basal cells convert to neurons
ensheathing cells
similar to glial cells
stem cells at the location of injury get 10 percent of function back into the spinal cord
pseudogenes
resemble genes similar to other species
