Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

bil 360 > 11c photoreception > Flashcards

11c photoreception Flashcards

1
Q

photoreception

A

a sensory cell’s response to light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

three functions of the simplest type of eye

A

photoreception

shading by dark pigment to allow detection of light direction

connection to motor structures to allow phototaxis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

define phototaxis and what a pos or neg phototaxis would mean

A

the bodily movement of a motile organism in response to light, either toward the source of light ( positive phototaxis ) or away from it ( negative phototaxis ).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

visible spectrum

A

Electromagnetic waves falling in the range that can stimulate an animal’s photoreceptors comprise that animal’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

why does the visible spectrum vary between animal species?

A

bc it depends on the spectral sensitivities of their photoreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

visible spectrum range

A

390nm - 720nm, on average.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

pigment spot

A

simplest type of eye

adaptive for a facultative autotroph
allowed simple organisms to find light and dark with the help of the flagelllum

found in some protists (e.g., Euglena, Chlamydomonas)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

pigment cup

A

allows detection of light stimulus direction

in comparison to the pigment spot, it has more nerve fibers and the pigment cells are bended

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

optic cup

A

encloses a water filled cavity (pinhole opening)

reduces light scatter
increases resolution
found in many flatworms, rotifers, polychaetes, gastropods, chitons, and echinoderms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

deeper cup with a clear epithelial covering

A

further increases resolution

eye is protected from environmental toxins, pathogens

has a photoreceptor layer that will create the future retina

found in Chambered Nautilus (VERY SIMPLE CEPHALOPODS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

eye with primitive lens

A 
eye is able to focus incoming light 
eye can form clearer images 
has a now formed retina
has refractive lens
found in lampreys, fossil hagfishes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

complex eye aka camera eye

A

high resolution

has lens and a cornea

ability to form clear images
additional anatomical adaptations for color vision, etc.

compound eye found in insects and some crustaceans

camera eye found in all craniate vertebrates and cephalopod mollusks like an octupus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

spot vs cup

A

the cup has less of an opening which increases resolution and reduces distortion
and allows only a certain amount of light to come in

based on video… the cup also helps to avoid predators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

lens helps by

A

changing the curvature to adapt to n ear and far vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why do slow moving or sessile creatures have poor eyesight?

A

it is more dangerous to move so fast when practically blind so you might as well stay in place to protect yourself to avoid bumping into things

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

eyesight of slow moving or sessile creatures

A

simple eyes detect shadows and close movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

eye sight of slow mobile

A

eyes that aid in navigation, simple image formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

sight of the very fast

A

high visual acuity for accurate navigation, predation, predator avoidance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

vestigial remnants

A

primitive structure and no longer believed to be important for survival

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

define metazoans

A

any of a group (Metazoa) that comprises all animals having the body composed of cells differentiated into tissues and organs and usually a digestive cavity lined with specialized cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Hox gene, PAX6

A

encodes a transcription factor essential for brain and eye development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

does loss of function in the pax gene effect as homozygous or heterozygous?

A

effects both and two pox genes that are loss will cause failure of eyes to develop at all

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

rhabdomeric photoreceptors - (for protostome invertebrates)

A

maximize membrane surface area with microvilli projecting from the apical surface

apical surface is rotated 90o with respect to ancestral position

This lateral bed of (dendritic) microvilli form the rhabdom.
can vary in shape

second messenger signal transduction via
phospholipase C (PLC)/inositol phosphate (IP3) pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are the specialized phtotoreceptor cells that detect and transduce light?

A

rhabdomeric and cilliary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
ciliary photoreceptors
maximize membrane surface area via highly folded cilium (outer segment) projecting from the apical surface of the cell body form rod and cone photoreceptors use glutamate as a neurotransmitter second messenger signal transduction via phosphodiesterase (PDE) altering [cGMP] pathway
26
cillary vs rhabsomeric
rhabodemeric - used for invertebrates - SA increases with microvilli - secondary messenger is phospholipase C (PLC)/inositol phosphate (IP3) pathway ciliary - used for vertebrates - SA increases with cilium - phosphodiesterase (PDE) altering [cGMP] pathway
27
macula degeneration
can be wet or dry wet= get vascularization of retina which u don't want blood getting in the way of where light is coming from definition: if u lose all of the photoreceptors, u will go blind
28
define rhabdom
This lateral bed of (dendritic) microvilli which act as the receptors
29
cause of blind spot
The natural blind spot (scotoma) is due to lack of receptors (rods or cones) where the optic nerve and blood vessels leave the eye.
30
what creature has both rhabdom and ciliary photoreceptors?
Ancestral bilaterians and larva platenera
31
role of each photoreceptor in planaris larva
The eyes contain rhabdomeric photoreceptors. These enable the larvae to detect and swim towards light sources. ultraviolet light activates ciliary photoreceptors, whereas cyan, or blue-green, light inhibits them. Shining ultraviolet light onto Platynereis larvae makes the larvae swim downwards. By contrast, cyan light makes the larvae swim upwards. In the ocean, ultraviolet light is most intense near the surface, while cyan light reaches greater depths. Ciliary photoreceptors thus help Platynereis to avoid harmful ultraviolet radiation near the surface.
32
ommatidum
contains six to eight sensory receptors arranged under a cornea and refractile cone and is surrounded by pigment cells, which adjust the intensity of light. Each ommatidium can act as a separate eye and is capable of responding to its own visual field.
33
describe the arthropod/insect compound eye
Insect eyes can contain 3000 (fruitfly) - 25,000 (dragonfly) rhabdomeric photoreceptors per eye. The compound eye is composed of multiple ommatidia, each containing multiple photoreceptor cells.
34
describe the Cephalopod Camera Eye
The cephalopod retina contains 20,000 - 50,000 | rhabdomeric photoreceptor cells/mm2.
35
describe the vertebrate camera eye
The vertebrate retina contains millions of ciliary photoreceptor cells. Many vertebrates have a recessed structure, the fovea, which is the point of highest visual acuity. The human fovea has ~200,000 photoreceptors/mm2 . The avian (bird) fovea may have 400,000 - 1,000,000 photoreceptors/mm2, depending on species. Raptors (birds of prey) have two foveas (shallow and deep foveas where the deep one helps with acuity) . Lots of dots!
36
define fovea
a small depression in the retina of the eye where visual acuity is highest
37
pigment
is a substance that changes the color | of reflected or transmitted light via wavelength-selective absorption.
38
photopigment
biological pigment used by a living organism to absorb light.
39
absorption spectrum
The range of wavelengths that a photopigment can potentially absorb comprise the
40
action spectrum
The range of wavelengths capable of driving a biological process is the
41
the pigment is responsible for facilitating that process IF
Close correspondence between the absorption spectrum of a pigment and action spectrum of a biological process associated with that pigment
42
what is the peak of the wavelength of the relative absorption?
500 nm
43
chromophore (11-cis retinal)
Vitamin A (all-trans retinol) is converted in the retina to the 11-cis-isomer of retinaldehyde or 11-cis-retinal. 11-cis-retinal functions in the retina in the transduction of light into the neural signals necessary for vision. The 11-cis retinal in photoreceptors is covalently bound to an opsin signaling protein to form a visual pigment molecule. In the presence of light, 11-cis retinal is isomerized to all-trans retinal, and the straightening of the polyene chain activates the opsin
44
opsin
a protein which forms part of the visual pigment rhodopsin and is released by the action of light. determines the wavelength of light to which pigment is sensitive is a protein - encoded by DNA, so variable... among species among individuals of the same species within a single individual All are members of the G protein-coupled receptor (GPCR) superfamily.
45
chromophore
The prosthetic group (chromophore) confers light sensitivity to the protein.
46
Type I opsins
bacteria and some algae (all-trans chromophore)
47
Type II opsins
all eumetazoans (11-cis chromophore)
48
Upon isomerization
visual pigments trigger a metabotropic | second-messenger cascade, eliciting a receptor potential
49
rhodopsin
ancient G-protein coupled receptors. vertebrate rod photoreceptor pigment extremely light sensitive photobleaches upon exposure to light returns to unbleached isomer in absence of light confers high sensitivity to light/night vision
50
blue cone
Short Wavelength Senstive (SWS) Opsin has a λmax of 430nm.
51
green cone
Medium Wavelength Sensitive (MWS) Opsin has a λmax of 530nm.
52
red cone
Long Wavelength Sensitive (LWS) Opsin has a λmax of 560nm.
53
blue photopsin vs rhodopsin
many amino acid substitutions
54
green photopsin vs red photopsin
many amino acid substitutions
55
red photopsin vs green photopsin
many identical amino acids
56
plural of rhabdomere
rhabdome
57
what insect has more ommatidia/unit area than any other arthropod.
dragon fly compound eye As aerial predators, they have evolved high visual acuity that allows them to localize and capture small, flying prey in mid-flight.
58
light gathering in the ommatidium
outer/top section -cornea, derived from cuticular corneagen (epidermal cells that take mucus from cornea mold formed) cells -crystalling cone, derived from cuticular Semper's (cone cells) cells These focus incoming light onto the photoreceptor of the crystal part
59
light-sensing segment (photoreceptor)
lower/bottom section -light goes to 7-8 rhabdomeric retinula cells (photosensitive cells) -Microvilli (dendritic processes) form the rhabdomere of each cell. Rhabdomeres converge in the center to form the rhadom.
60
iris
prevent light from scattering among ommatidia, isolating each ommatidium from its neighbors.
61
optic nerve aka cranial nerve II
transfer visual information from the retina to the vision centers of the brain via electrical impulses. Retinula cell axons pass through a basement membrane
62
protocerebrum
(visual center), located in the anterior portion of the brain where visual stimuli are processed and output is generated.
63
location of primary and secondary iris/pigment cells
closest to the cornea: primary iris/pigment cells closest to the base:
64
what two types of ommatidum compound eye have?
photopic (apposition) | scotopic (superposition)
65
photoptic
have a crystalline cone touching (in apposition to) the rhabdome are the most common type of compound eye are found in diurnal insects have low sensitivity to light confer high resolution have relatively short ommatidia, each of which has a relatively small field of view produces an inverted image The rhabdom averages the light received by the eye. Multiple, inverted images are combined (and flipped) in the brain
66
scopotopic
have a "clear zone" between crystalline cone and rhabdom The "clear zone" contains crystalline tracts These arise from retinula cells and act as "light guides"
67
phototopic vs scopotopic
phototopic is during the day time so it is diurnal, very common, has low sensitivity, high resolution, short ommitilda, and has inverted images scopotopic is the opposite
68
causes of photopic having short ommatilda?
has a relatively small field of view produces an inverted image The rhabdom averages the light received by the eye.
69
eff of scopotopic having long ommatilda?
At night, pigments in secondary pigment cells migrate to cell apices Incoming light can stimulate unshielded rhabdomes of neighboring ommatidia Images from each ommatidium are superimposed on each other. Visual input to the brain comprises a single, un-inverted image.
70
cornea
transparent, colorless "window" transmits light into the eye helps focus light onto the retina.
71
pupil
aperture (hole/opening) through which light enters the eye
72
iris
pigmented "shutter" contracts or relaxes to change aperture, controlling light admission.
73
lens
transparent, colorless crystalline disc fine-focuses light onto the retina.
74
anterior chamber / segment
fluid-filled space between cornea and iris
75
anterior humor
fluid in the anterior chamber
76
posterior chamber/segment
fluid-filled space between lens and retina
77
posterior humor
aqueous gel in the posterior chamber
78
retina
layer of specialized neurons that lines proximal interior of the eyeball senses light, generates RPs and APs that travel through the optic nerve to the brain
79
fovea
small, recessed retinal spot with the highest cone density and thus, highest visual acuity
80
macua
(primates only) unrecessed retinal spot with a high density of cone photoreceptors, and housing the fovea.
81
facet
corneal lens for individual ommatidium
82
primary iris/pigment cells
closest to the cornea
83
secondary iris/pigment cells
closest to the base:

bil 360 (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions