Lesson 2 - Part 2 - Special Senses Flashcards
(156 cards)
1
Q
vision (sight)
A
perception of objects in the environment by means of light they emit or reflect
2
Q
light
A
visible part of the electromagnetic spectrum
3
Q
light must cause a _____ reaction to produce a nerve signal
A
photochemical
4
Q
ultraviolet radiation
A
< 400nm, has too much energy and destroys macromolecules
5
Q
infrared (IR) radiation
A
> 700 nm, too little energy to cause photochemical reaction, but does warm the tissues
6
Q
orbital region
A
area around the orbit (eye socket), contain structures that protect and aid the eye
7
Q
eyebrows
A
enhance facial expression, protect eyes from glare and perspiration
8
Q
eyelids (palpebrae)
A
consist of orbicularis oculi muscle and supportive fibrous tarsal plate
9
Q
medial and lateral commissures
A
where the eyelids meet on the medial and lateral sides of the eyes
10
Q
eyelids are covered with _____ outside and _____ inside
A
skin, conjunctiva
11
Q
tarsal glands
A
secrete oil that reduces tear evaporation and prevents the eyelids from sticking together
12
Q
eyelashes help….
A
keep debris out of the eye
13
Q
conjunctiva
A
transparent mucous membrane lining the eyelids and covering the anterior eyeball, expect the cornea
14
Q
conjunctivitis
A
pinkeye, inflammation and associated redness caused by allergic reaction, chemical irritations, or an infection by a pathogen
15
Q
what does the conjunctiva do?
A
secretes a thin mucous film to prevent the drying of the eyeball
16
Q
lacrimal apparatus
A
gland and tear ducts for production and drainage of tears
17
Q
lacrimal gland
A
in superolateral corner of the orbit, it secretes tears
18
Q
tears
A
slightly alkaline, watery secretion containing antibodies and bactericidal lysozyme; washes over and lubricates the eye, delivers oxygen and nutrients to conjunctiva
19
Q
lacrimal punctum
A
opening on the eyelid edge
20
Q
how do tears flow through the eye? (4)
A
- lacrimal punctum
- lacrimal sac
- nasolacrimal duct
- empty into the nasal cavity
21
Q
lacrimal caruncle
A
mass of soft tissue containing glands that produce a thick secretion that forms into a gritty deposit (you discover after waking up)
22
Q
orbital fat
A
cushions the eye, protects vessels and nerves
23
Q
extrinsic eye muscles
A
attach to exterior surface of the eye
24
Q
rectus muscles
A
superior, inferior, medial, and lateral rectus
25
oblique muscles
superior and inferior
26
all of the extrinsic eye muscles (6)
- superior rectus
- inferior rectus
- medial rectus
- lateral rectus
- superior oblique
- inferior oblique
27
what cranial nerves innervate the extrinsic eye muscles? What muscles do they innervate? (3)
- IV innervates superior oblique
- VI innervates lateral rectus
- III innervates other four extrinsic muscle
28
how does the superior rectus move the eyeball?
up
29
how does the inferior rectus move the eyeball?
down
30
how does the medial rectus move the eyeball?
medially
31
how does the lateral rectus move the eyeball?
laterally
32
how do the superior and inferior obliques turn the eye?
turns the 12 o'clock pole of each eye toward or away from the nose; they also produce slight elevations and depressions of the eye
33
three tunics of the eye
1. fibrous layer
2. vascular layer
3. inner layer
34
fibrous layer of the eye (3)
outer layer derived from two regions
- sclera
- cornea
- corneal limbus
35
vascular layer of the eye
uvea; middle layer with three regions
- choroid
- ciliary body
- iris
36
how does the ciliary body support the eye?
it supports the lens and iris by secreting aqueous humor
37
how does the pupil dilate?
dilation of the pupil caused by sympathetic stimulation of pupillary dilator muscle
38
how does the pupil constrict?
constriction of the pupil is caused by the parasympathetic stimulation of the pupillary constrictor muscles
39
what causes a dark iris?
a lot of melanin in chromatophores
40
chromatophores
iris pigmented cells
41
choroid
highly vascular, darkly pigmented layer behind the retina that provides oxygen and nutrients to the retina
42
ciliary body
extension of the choroid, a muscular ring around the lens
43
iris
colored diaphragm controlling the size of the pupil
44
functions of the uvea (4)
1. provides route for blood/lymphatic vessels that supply the eye
2. regulates amount of light entering the eye
3. secretes and reabsorbs aqueous humor that circulate within the anterior cavity of the eye
4. controls the shape of the lens to focus light onto the retina
45
sclera
tough, fibrous protective layer; the white of the eye
46
cornea
anterior transparent region; admits light into the eye
47
corneal limbus
border separating the sclera from the cornea
48
inner layer of the eye
retina and pigmented epithelium located next to choroid of the uvea
49
what does the pigmented epithelium do?
absorbs light that passes through the inner neural layer and prevents light from bouncing back into the retina
50
the inner layer contains what specialized cells?
photoreceptors called rods and cones
51
rods
do not detect different wavelengths (cannot detect colors); however, very sensitive to light, used in low light surroundings
52
cones
provides color vision; cones clustered at fovea centralis at the center of the macula lutea
53
cornea
transparent window allowing light into the eye, the initial refraction of light occurs here
54
aqueous humor
serous fluid secreted by ciliary body into the posterior chamber between the iris and lens
55
posterior chamber of the eye
the area between the iris and the lens
56
anterior chamber of the eye
the space between the iris of the cornea
57
scleral venous sinus
reabsorbs aqueous humor at the same rate at which it is secreted
58
where are the anterior and posterior chambers located?
located in the anterior cavity of the eye
59
lens
transparent structure composed of flattened compressed transparent cells called lens fibers
60
suspensory ligament
the ligament connected to the ciliary muscles of the ciliary body
61
what does contraction of the ciliary muscle do?
loosens the suspensory ligament and causes lens to become thicker/rounder to focus near objects
62
what does relaxation of ciliary muscle do?
muscle tightens the suspensory ligament and causes lens to flatten to focus on far objects
63
vitreous body
gelatinous substance that fills the vitreous chamber (posterior cavity) located behind lens
64
what does the vitreous body maintain?
intraocular pressure; helps hold the retina against the wall of the eye and blood supply
65
what are lens fibers filled with?
crystallins, which provides transparency to the lens
66
cataracts
clouding of the lenses
67
cataracts consists of....
- lens fibers darken with age
- fluid filled bubbles and clefts filled with debris appear between the fibers
68
treatment for cataracts
replacing natural lens with plastic one
69
what can cataracts be induced by? (5)
- diabetes
- smoking
- drugs
- ultraviolet radiation
- certain viruses
70
glaucoma
pressure within the eye due to obstruction of scleral venous sinus causing improper drainage of aqueous humor and increased intraocular pressure
71
what does glaucoma cause?
this causes compression of blood vessels and lack of oxygen and death of retinal cells (peripheral vision is first affected)
72
macular degeneration
death of photoreceptor cells in macula lutea (central part of the retina)
73
what does macular degeneration cause?
loss of vision in the center of visual field
74
can macular degeneration be cured?
no, but its progression can be slowed
75
diabetic retinopathy
retinal degeneration caused by effects of diabetes mellitus; causes blockage of normal retinal blood vessels and growth of abnormal vessels and blood leakage into the posterior cavity
76
what causes the most cases of adult blindness in the US?
diabetic retinopathy
77
optic disc
medial to macula lutea where the ganglion cell axons converge and leave the eye as the optic nerve
78
blind spot
the optic disc where no photoreceptor cells are located
79
visual filling
brain fills in the blind spot area
80
scotomas
abnormal blind spots (blind spots in areas in other than the optic disc)
81
causes of scotomas (3)
- compression of optic disc
- damage to photoreceptors
- damage to the visual pathway
82
visual process
light enter the eye, focused on the retina, and produces a tiny inverted image
83
what two sets of contractile elements control iris diameter?
- pupillary constrictor
- pupillary dilator
84
pupillary constrictor
smooth muscle encircling the pupil
85
parasympathetic stimulation to the pupillary constrictor does what?
narrows the pupil
86
sympathetic stimulation to the pupillary dilator does what?
widens the pupil
87
pupillary dilator
spoke-like myoepithelial cells located distal to the pupil compared to pupillary constrictor muscle
88
what do pupil constriction and dilation occur in response to? (3)
- emotions
- changes in light intensity
- when gaze shifts between distant and nearby objects
89
photopupillary reflex
pupillary constriction in response to light
90
refraction
bending of light =
91
refractive light index
of a medium; how much a substance retards light rays
92
the _____ refracts light more than the _____
cornea, lens
93
astigmatism
condition where light passing through the cornea and lens is not refracted properly causing visual distortions
94
emmetropia
normal vision where the eye is relaxed and focused on object more than 20ft away
95
near response
adjustment to close-range vision
96
three steps of near response
1. convergence of eye
2. constriction of pupils
3. accommodation of lenses
97
near response: convergence of the eyes
eyes orient their visual axis
98
near response: constriction (miosis) of the pupil
blocks peripheral light rays and reduces spherical aberration
99
spherical aberration
blurry edges
100
near response: accommodation of the lens (3)
change in the curvature of the lens
- ciliary muscles contract, suspensory ligaments slacken, and lens takes more convex shape
- light is refracted more strongly and focused onto the retina
101
hyperopia
farsightedness; far objects appear clear, but nearby objects are blurry
102
presbyopia
age-related hyperopia in adults 40+
103
myopia
nearsightedness; nearby objects appear clear but far objects are blurry
104
pigmented layer (pigmented apithelium)
most posterior part of retina; absorbs stray light so visual image is not degraded
105
neural components of the retina: photoreceptor cells
rods, cones, and certain ganglion cells
106
photoreceptor cells
absorb light and generate a chemical electrical signal, but are not neurons
107
bipolar cells
synapse with rods and cones, serve as first-order neurons that carry signal to ganglino cells
108
ganglion cells
second-order neurons of the visual pathway; their axons form the optic nerve
109
outer segment of rods and cones
points toward the wall of the eye, towards the pigmented layer, and contains modified cilium specialized to absorb light
110
inner segment of rods and cones
facing the interior of the eye; contains organelles and gives rise to cell body and process that form synapse
111
rods
responsible for night (scotopic) vision, produces images in shades of grey
112
monochromatic vision
images produced by rods are in shades of grey
113
rhodopsin
the visual pigment in the outer segment of rods
114
cone
responsible for day (photopic) vision and color (trichromatic) vision
115
the outer segment of cones contain discs that are plasma membrane infolding that contain...
pigments for light absorption
116
where do rods and cones continually renew their discs?
new ones add to the proximal (basal) end of the outer segment, old discs shed from the distal tips of the cells and are phagocytized in the pigment epithelium
117
horizontal cells
don't form separate layers in the retina; modulates information from photoreceptors to bipolar cells
118
amacrine cells
don't form separate layers in the retina; modulates information from bipolar cells to ganglion cells
119
neural convergence
multiple rods or cones synapse on one bipolar cells and multiple bipolar cells synapse on one ganglion cell
120
retinitis pigmentosa
most common inherited visual problem; caused by a mutation in a visual pigment that results in photoreceptor cells death, and ultimately blindness
121
two major parts of rhodopsin
- opsin protein and retinene (retinal) derived from vitamin A
122
where is opsin in rods?
embedded in disc membranes of the outer segment
123
nyctalopia
night blindness, can be caused by a dietary vitamin A deficiency
124
all rods contain a single kind of rhodopsin that _____ distinguish color
cannot
125
cones contain a pigment called
photopsin
126
the different parts of opsin in cones contain
different amino acid sequences that determine wavelengths of light absorbed
127
three types of cones
red, green, blue
128
how do red, green, and blue differ?
each type expresses a different type of opsin, therefore absorbs slightly different wavelengths of light
129
how does the brain determine color?
it compares the response levels across all three types of cones to determine color
130
light adaptation
adjustment in vision when moving from a dark or dim area into brighter light
131
what is the time needed for pigment bleaching to adjust retinal sensitivity to high light intensity?
5 to 10 minutes
132
dark adaptation
adjustment to vision when moving from a bright area into a dark or dim area
133
how long does it take for night vision to start working?
1-2 minutes
134
when does night vision reach peak sensitivity?
20-30 minutes
135
duplicity theory of vision
a single receptor system cannot produce both high sensitivity and high resolution; explains why we need rods and cones
136
spatial summation
onge ganglion cell receives info from 1mm^2 of retina producing only a coarse image
137
edges of the retina have widely spaced rods that act as
motion detectors; low-resolution systems only, cannot resolve finely detailed images
138
what happens to rods when light is bright enough to have color vision?
rods are photobleached and not contributing to vision
139
the fovea has no, what?
no neuronal convergence, each cone has its "private line to the brain"
140
color blindness
hereditary alteration of lack or one photopsin or another
141
red-green color blindness
results from a lack of either red or green cones since the individual has difficulty distinguishing shades of red and green
142
stereoscopic vision (stereopsis)
depth perception, the ability to judge distance to objects
143
what does stereoscopic vision require?
two eyes with overlapping visual fields which allows each eye to look at the same object from different angles
144
fixation point
point in space which the eyes are focused
145
first-order neurons of the retina
bipolar cells
146
second-order neurons of the retina
retinal ganglion cells
147
axons exiting the back of each eye leave the eye as which nerve?
the optic nerve, CN II
148
hemidecussation
half the fibers from each optic nerve cross over at the optic chiasm
149
optic tracts
fibers come together after the chiasm to form the right and left of these
150
the optic tracts pass laterally around the hypothalamus with most of their axons ending where?
lateral geniculate nucleus of the thalamus
151
third-order neurons arise and form the _____ _____ of fibers in the white matter of the cerebrum
optic radiation
152
what does the optic radiation do?
project to the primary visual cortex of the occipital lobe where conscious visual sensation occurs
153
where do some fibers of the optic radiation project? why?
hypothalamus to affect circadian rhythm
154
a few optic nerve fibers project to the midbrain and terminate in the _____ _____ and _____ _____
superior colliculi and pretectal nuclei
155
what does the superior colliculi control?
controls the visual reflexes and extrinsic eye muscles
156
what are the pretectal nuclei involved in?
photopupillary and accommodation reflexes
