special senses Flashcards
(206 cards)
1
Q
What is aguesia?
A
loss of taste
2
Q
What is anosmia?
A
loss of smell sensation
3
Q
What taste papillae are in the posterior part of tongue
A
Circumvallate and foliate
4
Q
taste papillae in anterior part of tongue
A
fungiform
5
Q
what do the sensory cells in taste buds project
A
microvilli into outer taste pore
6
Q
what are the properties of basal cells in taste buds
A
like stem cells
7
Q
what junctions are present in taste buds
A
tight junctions between apical membranes
8
Q
where are most taste receptors and channels
A
apical membrane of sensory cells
9
Q
what are on the basolat membrane of taste buds
A
calcium channels, stores and transmitter vesicles
10
Q
what are sweet, bitter and umami detected by
A
g protein coupled receptors
11
Q
what is salt detected by
A
Na+ entering cells leading to depolarisation
12
Q
what is sour detected by
A
H+ entering cells leading to depol
13
Q
what are the receptors involed in sweet and umami?
A
T1R
14
Q
what receptors for umami?
A
T1R1 and T1R3
15
Q
receptors for sweet
A
T1R2 and T1R3
16
Q
receptor for sweetener
A
T1R3
17
Q
what is the family of receptors in bitter
A
T2R
18
Q
why is it important to have many bitter receptors
A
tells us if it is poisonous
19
Q
what do T1R and T2R act via
A
TRP channel M5 which allows entry of cations leading to depolarisation
20
Q
What is the aqueous solubility of an odorant increased by?
A
OBPs (odorant binding proteins)
21
Q
do olfactory receptor neurones have cilia?
A
yes, project into mucus
22
Q
where are receptors for odorants located
A
cilia of the ORN
23
Q
what is the function of the supporting cells in the ORN
A
determine the composition of the mucus
24
Q
how many ORNs per nostril
A
6 million
25
each ORN has how many non motile cilia
8-20
26
how is an odour molecule transported to a receptor
dissolves in olfactory mucus, OBP transports it
27
what is the process in olfactory transduction
olfactory G protein activated - adenylyl cyclase activated - cAMP increases- opens ion channels - influx Ca 2+ and Na+ - opens calcium dependent Cl- channels - depol of ORN - travels up cilia, summation - increases AP firing - olfactory bulb
28
where do ORNs synapse, what happens here
in the glomerulus, meet dendrites of mitral cells
29
how many types of neurone does each glomerulus receive input from?
one
30
what cells are involved in the sharpening of information of smell
periglomerular cells
31
what cells axons form the lateral olfactory tract
mitral cell axons
32
where do efferent fibres from higher brain centres synapse
granule cells
33
how many olfactory axons per glomerulus
25000
34
what is the convergence of ORNs to mitral cells
1000:1
35
what makes up the primary olfactory cortex
piriform cortex and entorhinal cortex
36
what makes up the secondary olfactory cortex
orbitofrontal cortex
37
what does smell have an subconscious effect via?
limbic system
38
what is the range for human hearing
20 Hz- 20kHz
39
what does the wall of the external auditory meatus contain
ceruminous glands (secrete cerumen- earwax)
40
properties of earwax
antibacterial, anti fungal
41
what angle does the tympanic membrane lie at
55 degrees. due to the handle of malleus draws it into a peak
42
what is the middle ear lined with
ciliated epithelium
43
what does the external auditory meatus end in
tympanic membrane- vibrates
44
role of the Eustachian tube
pressure equalisation, route for infection. connects middle ear and nasopharynx
45
what are the ossicles
malleus, stapes, incus
46
what is the role of the ossicles
impedance matching
47
what happens in impendance matching
tympanic membrane is a large surface area so weak force by the vibrations, concentrate onto a smaller area (1/20)
48
what is the area that concentrates the force in impedance matching
oval window (foramen ovale)
49
how much does the oval window increase sensitivity by
1000x
50
what regulates the movement of the ossicles
stapedius and tensor tympani
51
what bulges to allow vibrations to move from the inner ear to the cochlea
round window (fenestra rotunda)
52
what happens if there is trouble with the draining of the Eustachian tube
otitis media
53
what can lead to reduced acuity of hearing
anything restricting the movement of the ossicles- mucus in the inner ear, ossification of joints between ossicles
54
what range is the human ear most sensitive
1.5-3 kHz
55
what are the openings of the bony/ osseous labyrinth
central opening and round window
56
what arises on either side of the vestibule
semicircular canals on one side, spiral cochlea on the other side
57
what is the membranous membrane filled with
endolymph, rich in K+
58
where is endolymph secreted from
stria vascularis. endolymphatic sac regulates it
59
what fills the space between the outer wall of the membranous labyrinth and the bony
perilymph
60
what happens in the cochlea and how many turns
detection of vibrations. 2 3/4 turns
61
what is contained in the 2 outer chambers and the middle chamber
outer- NaCl, inner- Kcl
62
what does the central core of the cochlea contain
auditory fibres (CN8)
63
what forms the floor of the scala media
basilar membrane
64
how is the basilar membrane at the base and apex
base- narrow and taut, apex- broader
65
how far do high frequencies travel
not very far, they die out when they reach the floppy membrane
66
how far can low frequencies travel
the full length as the floppy membrane can sustain slower oscillations
67
what is tonotopy
pitch mapped by position. basilar membrane splits the complex sounds into component frequencies
68
what detects the vibrations running along the basilar membrane
organ of corti
69
how many rows compose the organ of corti
4 hair cells. 3 outer layers, 1 inner layer
70
what are the hair cells embedded in
tectorial membrane
71
what happens with the basilar membrane moves up and down
the hair cells move from side to side which is picked up by the tectorial membrane. release glutamate, stimulate dendrites of spiral ganglion
72
what is the function of inner hair cells
pitch determination. send freq info to the CNS
73
how many inner hair cells are there
3,500 (400 cells per octave)
74
what is the function of the outer hair cells
cochlear amplifier. increase sensitivity
75
how do outer hair cells work as a cochlear amplifier
contract when excited by waves along the basilar membrane. oscillate in phase with the bm, so amplifies the travelling wave
76
how many outer hair cells
12000
77
what happens if the ear is damaged
hair cells may oscillate without external sound so the basilar membrane vibrates and emits sound- humming.
78
what happens with difference tones (Tartini's)
2 tones present to the ear and hair cells move to produce a new peak
79
what is the frequency of a new tone in difference tones
difference between the two tones
80
what are difference tones used to diagnose
cochlear deafness show hair cell damage (distortion product otoacoustic emissions)
81
when can cochlear implants be used
if lost cochlear hair cell function but sensory neurones of spiral ganglion still functional
82
how do cochlear implants work
processor breaks down sound into frequency components. transmitted to implant receiver. conduct along wires to electrodes in the cochlea. stimulate nerve cells under the basilar membrane
83
what are part of the auditory pathway
superior olivary nucleus (MEDULLA); inferior colliculi (MIDBRAIN); medial geniculate nucleus (THALAMUS); auditory cortex
84
what is involved in sound source localisation
superior olivary nucleus
85
at what point in the pathway is the auditory reflex and what happens
inferior colliculi (turn head and eyes in response to a stimulus)
86
what tract is involved in the auditory pathway
lateral lemniscus
87
what is found in the primary auditory cortex
Heschl's gyrus. tonotopically mapped
88
what side is language processing on
left
89
what side is music, prosody and inflection of speech
right
90
what does the secondary cortex surrounding heschl's gyrus include
wernickes area
91
what is wernickes aphasia?
language fluent but meaningless words
92
what is brocas aphasia
language halting and non grammatical (as language produced in brocas)
93
what protects the ear from sound
stapedius muscle as limits the amount of movement of stapes
94
what happens in the stapedius reflex
if damaging levels it contracts to limit the movement of the ossicle chain and decrease the intensity of pressure pulses
95
is the ear better at protecting against low or high frequency sounds ?
better at blocking low frequency
96
what do low freq sounds mask
the higher sounds. so if intense low freq will perceive this as the low freq but if less low freq will perceive as a high freq
97
what happens when the stapedius is active
the higher frequencies are unmasked by the low frequencies and the perceived sound is quieter
98
what happens before we speak
stapedius reflex is initiated, so low frequencies can be attenuated
99
what is the threshold of human hearing
0dB
100
how much of an increase in energy carried by sound is there with each increase of 20bD
10x energy
101
what can exposure to very high levels lead to
at first temporary increase in hearing threshold, disturbances in hearing ringing and whistling. tinnitus, ear discomfort, muffled sounds
102
greater exposure leads to what
destruction hair cells. don't regenerate in mammals
103
what happens in damage to hair cells (noise induced hearing loss)
production of free radicals, increase in Ca2+, might not be sufficient blood supply, can lead to apoptosis
104
what does noise induced hearing loss first appear as
insensitivity at 4kHz (harder to interpret consonants here)
105
what happens when the ear is exposed to hair cells
disruption to hair cells; with longer exposure the cells begin to round up and shorten; after a while the remaining hair cells clump together into a single mass.
106
do axons project directly or indirectly to the outer hair cells
directly to outer (indirect mechanism to the inner cells)
107
what is the limit tor sound exposure over an 8 hour day
87 dB
108
with every 3dB increase in sound what happens to the length of exposure
halves
109
what is the outermost layer of the eye, what does it form anteriorly
sclera. forms the cornea
110
what is the role of the lens
focuses the image onto the back of the eye- on the retina
111
where is the image most focused
fovea (surrounded by macula lutea)
112
what is between the retina and the sclera. whats significant about it
choroid- vascular layer
113
where is the blind spot
where the optic nerve enters the eye- there are no photoreceptors. optic disc
114
features of sclera
tough, fibrous, opaqued, vascular, gives eye its shape
115
features of the cornea
transparent, curved, no blood vessels, well innervated, cont. with the conjunctiva
116
features of choroid
pigmented, well vascularised, supplies o2 and nutrients for retina
117
features of the ciliary body
attachment for lens suspensory ligaments, contains ciliary muscles, secretion aqueous humour forms the iris
118
what is the gel in the posterior chamber
vitreous body- attracts and holds water molecules (vitrein and hyaluronic acid)
119
what is in the anterior chamber
aqueous humour
120
how many layers makes up the retina
2- neural and photoreceptive layer and pigmented layer. one over ciliary process one over iris
121
how are the fibres arranged in the sclera
randomly orientated- collagen and elastic fibres and fibroblasts
122
does the sclera have epithelium
no except for the cornea
123
what are the layers of the cornea (from top to bottom)
epithelium, bowmans membrane, stroma, decemets membrane, endothelium
124
what is inflammation of the choroid
uveitis (as choroid is uveal tract)
125
what does the ciliary body do
secrete aqueous humour, attachment for lens suspensory ligaments. forms iris
126
what does the ciliary body contain
ciliary muscle fibres (parasymp)
127
how does the ciliary body drain
via the iridocorneal angle into the canal of Schlemm
128
what does the iris contain
constrictor and dilator muscles para and symp innervation, no epithelium on anterior surface.
129
what is the ora serrata
junction between retina and ciliary body
130
are there photo receptors past the ora serrata
no
131
role of the pigmented layer of the retina
recycling rods and cones
132
what is the lens held within
elastic capsule (collagen and proteoglycans)
133
what is the lens held under tension by
fibres of the ciliary zonule
134
why do lens become less transparent and finally opaque with age
as crystallins denature
135
what is a cataract
clouding of the lens
136
why are cataracts a common cause of blindness
as opaque lens prevents light passing and focussing on the retina at the back of the eye
137
what can cause cataracts
age related degenerative changes, diabetes, enzyme deficiencies, toxic side effects. treat remove lens replace with plastic lens
138
what is dry macular degeneration (90%)
tiny deposits of drusen on retina, few symptoms at first can get small dark spot in central vision as more drusen accumulate. can progress to worse
139
what is wet macular degeneration (10%)
rarer but worse. abnormal vessels beneath retina, may bleed and leak fluid building up beneath retina so bulges up damaging the eye. central vision blurry and distorted, progresses to severe vision loss
140
what happens in short focus of accomodation
ciliary muscle CONTRACTS and the body is brought forward; suspensory ligaments relax; lens becomes FATTER
141
what happens in long focus of accomodation
ciliary muscle relaxes; suspensory ligaments are under tension; lens becomes FLATTER
142
what is the term for long sighted and how is the eyeball
hypermetropia. too short light focuses behind the eyeball
143
what is the term for short sighted and how is the eyeball
myopia. too long the light focuses in front of the eyeball
144
what is required in long sighted and how to treat it
additional refractive power. converging corrective lens
145
what is requires in short sighted and how to treat it
negative refractive power. diverging corrective lens
146
why is presbyopia
lens thickens becomes harder with age. cant accomodate
147
what is astigmatism
lens or cornea not smoothly spherical
148
what happens in focussing
lens moves backwards and eyes inwards (convergence)
149
what is the cornea constantly doing
swelling- collagen fibres exert high osmotic swelling pressure
150
what are the endothelial and epithelial pumps on the cornea for
maintaining correct level of hydration
151
does the lens swell
yes has high swelling pressure. counteracted by epithelial fluid transport
152
what leads to cataracts
swelling of lens, also by UV light
153
what happens in light to dark light reflex what is it called
dilator pupillae muscle contracts. MYDRIASIS (symp)
154
what happens in dark to light light reflex what is it called
constrictor pupillae muscle contracts. MIOSIS (para)
155
what do rod and cone cells synapse with
bipolar cells, send info to ganglion cells
156
what cells perform lateral inhibition at the level of the photoreceptors and what is this process for
horizontal cells. sharpen the image and decrease input from neighbouring cells
157
amacrine cells perform lateral inhibition at the level of what cells
ganglion cells
158
what is the function of Muller cells
they act as light guides from the front to the back of the retina pass the light from the surface of the retina to the photoreceptor
159
where are most cones found
in the fovea (rods have an inverse distribution)
160
where are there no rods
in the fovea and blind spot
161
are there any photoreceptors in the blind spot
no
162
where is there overlap accounting for binocular vision
central area
163
where does the right visual field end up
on the left part of the retina of both eyes
164
what happens in partial decussation
at optic chiasm- all info from right visual field ends up in left visual cortex
165
what is cortical magnification
if stimulus in centre of visual field then large no of neurones process info from this small region however if it is seen in periphery processed by many less neurones
166
what happens in response to light hitting the photoreceptor
hyperpolarisation of photoreceptor
167
what neurotransmitter is released from the photoreceptor
glutamate
168
what are the 2 types of bipolar cell associated with the photoreceptor
hyperpolarising cells and depolarising cells
169
what happens if there is a decrease in glutamate
the hyperpolarising cells hyperpolarise (as usually it depolarises the cell) and the depolarising cells depolarise (as usually inhibits depolarisation)
170
what happens if it is linked to the depolarising cell
increase firing rate
171
what type of cells do photoreceptors synapse with
both rods and cones synapse with both- opposite responses at the retinal ganglion cells.
172
what happens in the dark (phototransduction)
HIGH levels cGMP. cation channels OPEN and Na+ and Ca2+ enter. 'dark current'. photoreceptors depolarise INCREASE in glutamate
173
what happens in the light (phototransduction)
LOW levels of cGMP. cation channels CLOSE. hyperpolarisation of the photoreceptor leads to decrease glutamate
174
what are the first and second parts of visual coding
first- form (detect edge of an object). 2nd- colour
175
what are the 3 types of cones
red, blue, green
176
what is the most sensitive to light of the 3 colours
red (559nm), then green (531nm), blue (419nm)
177
what are the channels for the colours of cones
red/green and blue/yellow
178
what are the different types of ganglion cells
X,Y and W
179
what are the X cells
80% ganglion ells. SLOW. CONES. central fovea
180
what are the Y cells
10%, FAST connected to rod cells
181
what are the W cells
detect light levels. involved in light reflex
182
what allows perception of depth
fusion of 2 images in the cortex from binocular vision
183
what are saccades
unconsciously move eyes compensating for poor imaging as not in focus as move away from centre of vision
184
which have larger outer segments (rods and cones)
rods have larger outer segments so there is a greater chance of trapping photons
185
if light levels fall what happens to cones
they become inactive and only rods respond, so colours begin to fade
186
is the central disc excited or inhibited by light
excited (outer disc inhibited)
187
what happens if light is shone on the inner and outer discs
inner- bursts of action potentials. outer- not much change in action potential
188
what is the function of the receptive fields of vision
sharpen edge of the field
189
where is the ganglion cell receptive field smallest
at the fovea. become larger as go towards the periphery
190
where does information coming from nasal hemifield go
crosses to the contralateral side of the brain. (info from temporal field remains ipsiateral)
191
where do most retinal axons travel to
thalamic lateral geniculate nucleus
192
how many layers of lateral geniculate nucleus are there
6 layers
193
what layers of the LGN are nasal contralat
1,4,6
194
what layers of LGN are temporal ipsilat
2,3,5
195
what are the 2 types of cell in LGN
magnocellular and parvocellular
196
what are the features of magnocellular of LGN (1 and 2)
large cells, ROD CELLS, low acuity, fast, high contrast
197
what are the features of parvocellular of LGN (3-6)
small cells, CONES, high acuity, slow, low contrast
198
where do axons of the LGN project
internal capsule; in optic radiation; along lateral ventricle; maintains retinopic order; into primary visual occipital cortex
199
what does the primary visual cortex analyse
edges
200
what does V4 analyse
colour vision
201
what does v3 analyse
dynamic vision
202
what does v5 analyse
motion
203
what is achromatopia
colour perception eliminated
204
what is the elimination of movement perception
akinetopsia
205
what is the elimination of ability to distinguish faces
prosopagnosia
206
what is horners syndrome
compression of the sympathetic chain leads to ptosis miosis anhydrosis
