special senses Flashcards
the extrinsic eye muscles
four recti muscles (superior, inferior, lateral, and medial), and two oblique muscles (superior and inferior)
where do the extrinsic eye muscles originate from?
the common tendinous ring
structures within the eye surface
palpebral fissure, lateral and medial commissures, lacrimal caruncle, sclera, and pupil
internal eye structures
vascular layer, inner layer, blindspot, anterior and posterior poles, iris, cornea, ciliary body, ciliary zonule, and macula lutea
palpebral fissure
the area between the open eyelids
lateral commissure
the corner of the eye when the eyelids meet at the lateral side
medial commissure
the corner of the eye where the eyelids meet at the medial side
lacrimal caruncle
the small, pink, globular spot at the inner corner of the eye; contains oil and sweat glands
sclera
the white coating of the eye; this is a tough, fibrous CT that extends from the cornea to the optic nerve at the back of the eye
what fibres are found in the sclera
elastic and collagen
pupil
centre of eye that allows light to enter; diameter is controlled by the smooth muscle of the iris
conjunctiva
a mucus membrane covering the sclera; this area is quite suspeticle to infection
the lacrimal apparatus
the tear system that is a group of glands, sacs, and ducts that make, secrete, and drain away tears
what is the function of tears
they work to hydrate, protect, and nourish the surface of the eye
another name for tears
lacrimal fluid
what are tears composed of?
mostly water and saline (salt), but also mucus, antibodies, and lysozyme
lysozyme
an enzyme that destroys bacteria and is found in tears
what are mucins?
a glycoprotein that acts as a lubricant to help the aqueous layer to spread evenly across the eye
what are mucins secreted by?
goblet cells
fibrous layer of the eye
outermost layer of the eye and includes the sclera and the cornea; sclera is the 5/6 and cornea is the 1/6
vascular layer of the eye
the middle layer which is mostly composed of the choroid, ciliary body, ciliary zonules and the iris
another name for the vascular layer of the eye
uveal
2 layers of the inner layer of the eye
the outer pigmented area and the inner neural layer
choroid
a darker layer of highly vascularised CT that provides a blood supply to the eyeball; also functions to absorb light to create more detailed vision; found in the middle layer
the inner layer of the eye
2 layers that contains the nervous tissue responsible for photoreception; this layer only exists in the posterior 5/6
2 other names for the inner layer of the eye
the retina or the neural tunic
blindspot of the eye
the point where your optic nerves and central vessels converge to exit the eye and into your brain; here there are no light sensitive cells that can detect light rays, so your retina cannot see this part; no cells because the nerve and vessels fill this space
another name for the blindpsot
the optic disc
anterior pole
the front of the eye where light enters; composed of the iris and the cornea
posterior pole
the part of the eye where light directly impacts the retina; where these is a high concentration of cones
iris
the coloured part of the eye that contains smooth muscle components that contracts or relaxes to change the diameter of the pupil; also contains elastic fibres
anatomy of the iris
contains elastic fibres and smooth muscle
cornea
bulge part of the anterior eye that is transparent; it allows light to enter, and along with the lens, it focuses light onto the retina; also contains Na pumps
anatomy of the cornea
stratified squamous epithelium and high concentration of nervous tissue
ciliary body
a muscular structure whose contraction causes the lens to take a more rounded shape and this is supported by the ciliary zonule
ciliary zonule
fine ligaments and fibres that attach the ciliary body to the lens and help to control contraction and maximise how light hits the retina
macula lutea
part of the retina that is responsible for sharp, detailed central vision; it contains a very high concentration of cones; located in the posterior pole
aqueous humour
clear fluid with the composition of blood plasma without blood cells; found in the anterior portion of the eye
vitreous humour
gel like substance in the posterior portion of the eye that helps support the lens and shape of the eye through creating pressure
similarities between rods and cones
both are photoreceptors and found in the innermost surface of the retina; both also contain photopigments but their specific types differ
rods
responsible for vision at low light levels, have low spatial acuity, and are not involved in colour
photopigment in rods
rhodopsin
spatial acuity
The ability to discriminate 2 stimuli close in space
cones
are active at higher levels, have high spatial acuity, and are involved in colour vision
photopigment in cones
Iodopsin
bipolar cell
cell in the retina that function to connect the photoreceptors to the retinal ganglion cell
how do bipolar cells work?
photoreceptors will change their membrane potential when stimulated by light energy, in which this alters the amount of neurotransmitter released onto bipolar cells; these cells will then connect to a retinal ganglion cell
where are ganglion cells located?
in the ganglion cell layer of the retina
retinal ganglion cells
these are a type of neuron that connect with photoreceptors via bipolar cells; they function to project retinal information to the rest of the brain
how do retinal ganglion cells transmit information to the brain?
their axons converge at the optic disc to form the optic nerve and eventually travel to the primary auditory centre in the brain
rhodopsin
the light receptor in rod photoreceptor cells of the retina that initiate scotopic vision
scoptic vision
night vision and is initiated by rods
photopic vision
vision under well-lit conditions and is initiated by cones
retinal
cofactor in an opsin molecule that undergoes a biochemical change when struck by a photon; it is a vitamin A debris molecule
two shapes of retinal
all-trans and 11-cis
phototransduction
the process by which light is converted into electrical signals by the retinal, travelling through the retinal network leading to the activation of ganglion cells which transmit information to the brain
what is phototransduction initiated by?
rods and cones
emmetropic, myopic, and hyperopic terms
all refer to refractive states of how light is focused onto the retina
emmetropic
these eyes are just the right length to allow light to be focused onto the retina to create clear, crispy vision
myoptic
these eyes are slightly too long, causing light to focus in front of the retina rather than directly on it; these individuals are nearsighted
what lens are used for myopic vision?
concave
what lens are used for hyperopic vision?
convex
what vision is nearsighted?
myoptic; causes distant objects to appear blurry
hyperopic
these eyes are a little too short, causing light to focus behind the retina; these individuals are farsighted
what vision is farsighted?
hyperopic; causes near objects to appear blurry
what is the olfactory epithelium?
an area that is responsible for transmitting odor information to the olfactory bulb in the brain
what are the three layers in the olfactory epithelium?
mucus membrane, columnar epithelium, and basement membrane (cilia also present here)
what is the function of mucus in the olfactory epithelium?
it traps and dissolves odorant molecules, allowing them to bind to olfactory receptors
cells found in the olfactory epithelium
olfactory receptor cells and basal cells (mitral cells located above but not part of epithelium)
where do gustatory sensory axons pass through?
the cribriform plate of the ethmoid bone
what do olfactory sensory cells synpase with?
mitral cells
what cells merge together to form the olfactory nerve?
the mitral cells
typical arrangement of a taste bud
they are located within the papillae of the tongue; also contain taste pores, gusatory hairs, basal cells, and gustatory receptor cells
3 cranial nerves associated with taste
facial, vagus, and glossopharyngeal
what are basal cells?
stem cells
the five flavours
sweet, salty, sour, bitter, and umami
external auditory canal
sound waves are directed to here and enter the skull through the temporal bone; is composed of cartilage and bone covered by skin
lobule
the fleshly lower part of the auricle; only parts that contains no cartilage and instead it is made of areolar and adipose tissue
tympanic membrane
separates the outer ear from the middle ear; when sound waves reach here they cause it to viberate and these vibrations are transferred to the tiny bones in the middle ear
function of the bones in the middle ear
to transfer the vibrating signals to the inner ear
another name for tympanic membrane
ear drum
three layers of the tympanic membrane
inner mucous membrane, middle fibrous layer, and outer cutaneous layer
malleus
bone of the ear that attaches to and moves with the tympanic membrane
incus
bone of the ear that receives vibrations from the malleus and transmits them to the stapes
stapes
bone of the ear that is the innermost and connects to the vestibular foramen; acts as the final chain in transmitting impulses from the external ear to the inner ear
smallest bone in the body
stapes
what are the ear bones called?
ossicles
what are bones composed of?
ground substance is hydroxyapatite (phosphorus and calcium), ECM is collagen and elastic fibres, and cells are osteoclasts, blasts, and cytes
cochlea
a fluid-filled, spiral shaped cavity found in the inner ear that plays a role in hearing and converts auditory signals to neural impulses
organ of corti
located within the cochlea of the inner ear and is responsible for converting sound vibrations into electrical signals that are transmitted to the brain; contains the basilar membrane and the tectorial membrane
auditory transduction
transmitting sound vibrations into electrical signals that are transmitted to the brain; cochlea is responsible for this
what cells make up the organ of corti?
sensory cells (hair cells) and supporting cells
similarities between semicircular canals and otolith organs
both are apart of the vestibular system that is located in the inner ear, and both play essential roles in maintaining balance and detecting head movements
semicircular canals
these detect rotational movement of the head, allow us to perceive rotational acceleration, and maintain dynamic balance; contains three semicircular canals
otolith organs
these detect linear acceleration, head position relative to gravity, and allow us to maintain static balance; contains two otolith organs
what special senses are chemical stimuli?
taste and smell
protein complex found in rods
retinal and opsin
how many alpha-helixes in opsin
7
what happens to photoreceptors when light reaches the retinal molecule?
retinal changes its configuration, causing opsin to also change its configuration
retinal in the presence of light
takes the all-trans shape
retinal in the absence of light
takes the 11-cis retinal shape
what is the G protein called in the occipital pathway?
transducin
what does the G protein in the visual pathway attach to?
transducin will diffuse across the cell membrane and attach to PDE
PDE
phosphodiesterase
what does PDE do?
converts cGMP into GMP in the visual pathway
what happens when cGMP levels fall
cGMP-gated cation channels close, resulting in hyperpolarisation
dark current
occurs when a depolarised state is created by the binding of cGMP to CNG channels, keeping them open
what is also called the organ of smell?
the olfactory epithelium
where is the olfactory epithelium located?
in the superior nasal cavity; allows for direct contact with the air passing through here
what enzyme does the G protein bind to in the gustatory pathway?
phospholipase C
function of adenylate cyclase
converts ATP to cAMP
function of cAMP
it opens up a cation channel in the olfactory pathway, allowing for an influx of Na and Ca, causing a depolarisation and then an action potential
frequency
the amount of waves per second; this determines the pitch
what determines the pitch?
frequency
amplitude
the difference in pressure for sound waves; this determine loudness of sound
what determines the loudness of sound?
amplitude
where is sound transformed to liquid?
in the ossicles before it arrives in the cochlea
what is the vestibular system associated with?
balance
visual pathway synapses two subtypes
nasal and temporal sides
nasal side visual pathway
the first order neuron decussates before it synapses with the thalamus; from here the second order neuron synapses in the cerebral cortex in the occipital lobe
temporal side visual pathway
the first order neuron synapses in the thalamus; from there it travels to the occipital lobe in the cerebral cortex; no decussation occurs
olfaction sensory pathway
first order neuron is the olfactory receptor cell which synapses with the second order mitral cell; this merges into the olfactory nerve which travels directly to the primary olfactory area in the cerebral cortex
unique features of the olfactory sensory pathway
no decussation and no synapse in the thalamus
taste sensory pathway
taste stimulus from the gustatory receptor cell (first order neuron) will synapse with the second order neuron in the gracile area of the medulla; this will synapse with the third order neuron in the thalamus which then travels to the primary gustatory area in the cerebral cortex; no decussation occurs
how many auditory sensory pathways are there?
3
what are areas of synapse in the visual pathway
thalamus and the cerebral cortex (decussation occurs in nasal side before the thalamus)
what are differences in the auditory visual pathway
neurons can either not decussate, can decussate and take two pathways, and can synapse in very inferior pons, decussate and travel straight to the inferior colliculus
nerve associated with the auditory system
the vestibulocochlear nerve
where do synapses occur in the auditory pathway?
the pons (twice usually), the inferior colliculus and the thalamus
2 sides in the cochlea
the scala vestibuli and the scala tympani
basilar membrane
receives auditory vibrations from the perilymph travelling through the cochlea and from this is determines frequency and amplitude which is transferred to the vestibulocochlear nerve
tectorial membrane
associated with the organ of corti and is a stable structure that helps with causing the hair cells to bend, creating action potentials for sound
how are action potentials created in the semicircular canals?
the canal rotates, but the fluid stays near the bottom, creating a force that bends the hair cells, creating an action potential
two parts of otolith organ
saccule and utricle
saccule
part of the otolith and determines vertical motion like jumping or being in an elevator
utricle
part of the otolith and determines horizontal motion like taking off in a plane
what special senses do not decussate
auditory sometimes, taste always, olfaction, and visual sometimes (temporal side)
what pathway decussates in the visual sense?
the nasal side
first and second portions of the cochlea
scala vestibuli then scala tympani
what is the scala tympani in contact with
the basilar membrane
perilymph
ECF located within the inner ear
two sides lining the organ of corti
the basilar membrane and the tectorial membrane
what side of the organ of corti is stationary
the tectorial membrane
three different axes for semicircular canals
shaking yes, shaking no, and tipping shoulders to ears
what are hair cells attached to in the semicircular canals?
ampula wall; in these structures are also stereocilia and support cells
anatomy of otolith organs
sheets of hair cells with CaCO3 embedded in gel at the tips of stereocilia
where do the extrinsic muscles of the eye attach to?
the sclera; one of the rare cases where the muscles do not attach to bone
order of flow for the lacrimal apparatus
the lacrimal gland will secrete tears, this will cross the conjunctiva to the lacrimal punctum, the lacrimal canaliculus, the lacrimal sac and then into the nasolacrimal duct
where do tears terminate?
the inferior meatus of the nasal cavity
where in the eye are Na pumps found?
the cornea
what is in contact with the choroid?
the pigmented inner layer
ora serrata
the serrated junction between the choroid and the ciliary body
fovea centralis
similar to the macula lutea and is a high concentration of cones in the posterior pole of the eye where visual acuity is the highest
where in photoreceptors are the pigments?
the outer segments and this area is embedded within the retina
do you have more rods or cones?
rods
why are no action potentials created in the dark
the depolarization causes a constant release of neurotransmitter, causing inhibitory postsynaptic potential in the bipolar cell and therefore no action potential along the optic nerve
how are action potentials created in the light?
cGMP channels are closed, causing a hyperpolarization which causes no release of neurotransmitter; this cause the bipolar cells to depolarize and for an action potential to be created
what is the G-protein called in the olfactory pathway?
golf
G protein for bitter, sweet, and umami
gustducin
what does gustducin bid to
phospholipase C
what does phospholipase C do?
creates IP3 which opens up calcium stores to create an action potential
sensory pathway for salty and sour
the excess of Na+ and H+ ions move in through channels in the membrane of the taste receptors and this causing a depolarization of the membrane and a release of neurotransmitter
pigmented layer
has photoreceptors embedded in it, and is similar to the vascular middle layer
bleaching on the pigment
light absorption by rhodopsin triggers a series of steps in which retinal changes from (from 11-cis to all-trans) and eventually releases from opsin
regeneration of the pigment
enzymes slowly convert all-trans retinal back to 11-cis in the pigmented epithelium and this requires ATP
when does bleaching of the pigment occur?
when retinal releases from opsin
how many types of cones are there?
3
what are the most abundant papillae
fungiform
where are the folate papillae found?
at the lateral sides
what nerve is associated with the anterior 2/3 of the tongue?
facial (VII)
what nerve is associated with the posterior 1/3 of the tongue?
glossopharyngeal (IX)
what nerve is associated with epiglottis taste sensation?
vagus nerve (X)
what is the primary sense processed in the brain?
vision; 70% of sensory receptors in our bodies are in our eyes and half of the cerebral cortex processes vision
term for eyelid
palpebrae
what is found in the lacrimal caruncle?
sweat and sebaceous glands
what are the corners of the eyes called?
commissures
what kind of muscles are found in the iris
smooth muscle sphincters; contains circular and radial fibres; also contains elastic fibres
what feeds into the lacrimal canaliculi
the lacrimal punctum
anatomy of the cornea
outer stratified squamous epithelium and inner simple squamous which contains Na+ pumps to clear fluid clear; also contains nerve endings
what eye layer is only found in the posterior 5/6?
the retina
where does the retina end?
the ora serrata
where does aqueous humor come from?
capillaries of ciliary processes; it is constantly formed and drained
where is aqueous humor drained from?
the scleral venous sinus
functions of the vitreous humor
helps to support the lens from pressure, creates pressure to hold eye shape, and helps with the transmission of light through having clear composition
what forms the optic nerve?
the axons of ganglion cells
why is rhodopsin called rhodopsin?
because it is a combination of retinal and opsin
where is retinal derived from?
vitamin A
what kind of protein in opsin
a transmembrane protein
what is the default activating state for bipolar cells
no neurotransmitter release
anatomy of olfactory epithelium
pseudostratified ciliated epithelium with olfactory receptor cells, basal cells, supporting cells, and mitral cells
cilia in olfactory epithelium
non-motile and where receptor proteins are found; these increase surface area
support cell in olfactory epithelium
columnar cells that secrete mucus
bone in olfactory epthelium
cribriform plate of the ethmoid bone
circumvallate papillae
least numerous but largest, found in frontal plane direction sort of in the middle/back of tongue
epithelium of the tongue
stratified squamous epithelium
what makes something bitter?
high alkaline profiles
what makes something umani?
amino acids
what makes something salty?
metal ions
what is the tympanic membrane made of?
CT
amplify the vibration meaning
transforms air to liquid in the ossicles before reaching the cochlea
what is the mechanoreceptor for semicircular canals
a hair cell attached to a stereocilia
what structure senses head movement and what structure senses head postion
head movement is sensed by the canals and position by the otolith organs
what are the CaCO3 crystals called in otolith organs?
otoliths
what kind of gland is the lacrimal gland?
exocrine gland
what does the conjunctiva secrete?
mucus
where is the macula lutea located?
lateral to the blindspot
how thick is the pigmented layer?
a single layer of epithelium
name of hair cells in the organ of corti
sterocilia
what are taste hairs?
microvilli of gustatory cells
what is the stapes in contact with?
the oval window
what is the exit of the cochlea called?
the round window
what side of the organ of corti are the hair cells embedded in?
the tectorial membrane
is the utricle or saccule more superior in the ear?
urticle
what are the vestibular organs attached to?
the oval window and the stapes
