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