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Vertebrates 305 > Vertebrates 19 - Vision > Flashcards

Vertebrates 19 - Vision Flashcards

1
Q

Median eyes

A

pineal or parietal organs. Not image forming, just sense brightness and the duration of light. Connect to pineal gland

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2
Q

Pineal glad

A

Produces melatonin most when dark. In mammals it reads from the retina instead of pineal eyes.

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3
Q

Melatonin

A

Affects circadian rhythms. Metamorphosis in amphibians, sexual cycles (with change in seasons), skin pigment changes in amphibians

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4
Q

Image forming eyes

A

Real eyes. Durr.

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5
Q

Sclera

A

Outer layer, white part. Holds everything else in.

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6
Q

Coroid layer

A

Blood vessels, pigmented epithelia. Pigment can absorb or reflect light.

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7
Q

Tapetum lucidum

A

Reflective layer in coroid layer made of guanine crystals. Reflects light so it can activate photoreceptors better, but image is a bit less clear. Important for nocturnal animals.

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8
Q

Fovea

A

Highest concentration of photoreceptors

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9
Q

Optic disk

A

Blind spot where optic nerve is. Can see images here.

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10
Q

Vitreous humour

A

Supports lens and retina.

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11
Q

Aqueous humour

A

B/w cornea and lens.

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12
Q

Cornea

A

Allows light to pass through

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13
Q

Lens

A

Focuses light onto the retina.

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14
Q

Ciliary body

A

Affects size/shape of the lens to focus the light.

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15
Q

Iris

A

Control amount of light entering eye through pupil.

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16
Q

Pupil shapes

A

Goats/sheep - horizontal; snakes, cats - vertical

17
Q

Eyelid

A

Skin for protecting the eye

18
Q

Nictitating membrane

A

“third eyelid”, covers most of eye. Can be under the eyelid (cat) or without eyelid (shark).

19
Q

Retina

A

Pigmented layer. Photoreceptors go to bipolar cells to ganglion to nerve. A few other things to integrate info before the brain.

20
Q

Retinal pathway

A

Optic nerve to the optic chiasm where R and L cross and split. Processed in the visual cortex on the opposite side from eye. Thalamus is relay center to occipital lobe or superior colliculus

21
Q

Superior colliculus

A

Coordinates motor movements of eyes. Connected to the thalamus.

22
Q

Photoreceptors in the eye

A

Rods and cones. Have cell bodies to produce proteins etc, and the outer segment which is important in sensing light. Contain second layer of membrane called membrane disks

23
Q

Membrane disks.

A

In the outer segment. Contain rhodopsins: protein part (opsin) and retinal (Vit A derivative)

24
Q

Rods

A

high sensitivity, low acuity, 400-600nm

25
Q

Cones

A

low sensitivity, high acuity (detail). Usually sensitive to only one wavelength.

26
Q

Cone types

A

Depend on the rhodopsin (specifically the opsin, retinal is same) Blue (450nm), Green (525nm), Red (650nm), some UV (360nm)

27
Q

Tetrachromats

A

Have 4 cones. Birds and lizards

28
Q

Dichromats

A

Have 2 cones. Most mammals. Lost 2 rhodopsins to reach this.

29
Q

Trichromats

A

Have 3 cones. Include primates, humans. Gained a 3rd after ancestor lost 2.

30
Q

Evolution of mammals and vision

A

First mammals were nocturnal etc. Colour helped gain access to new food etc.

31
Q

Phototransduction in Dark

A

Increase cGMP, opens Na channel (dark current channel), flow in. Depolarize the cell, release glutamate to transmit signal

32
Q

Phototransduction in Light conditions

A

Retinal converted from cis to trans, elongates and changes shape of rhodopsin, activates transducin, activates phosphodiesterase, makes cGMP to GMP, Na channel doesn’t stay open, repolarizes membrane.

33
Q

Compare Phototransduction in light and dark

A

Dark: depolarized, Na open, inactive rhodopsin, glutamate released. Light: Na closed, active rhodopsin, hyperpolarized

34
Q

Terrestrial eyes

A

Tear glands for moisture, cornea and lens involved in refracting light, thin lens, eyelids (1 or more), some have nictitating membrane, fast pupillary response (more changes), variable number of rods/cones, tapetum lucidum in some

35
Q

Aquatic eyes

A

No tear glands, Cornea does not refract (water does), lens does, round lens, most have no eyelids, some have nictitating membrane, slow pupillary response (generally constant), mostly rods (less light), tapetum lucidum in some

36
Q

Eyelid

A

Helps protect the eye as well as help get moisture across the eye.

37
Q

Eyes on side

A

Little overlap, but greater field behind. Defense in prey species (rabbits, shore birds, chameleons)

38
Q

Binocular vision

A

Both in front: greater binocular vision, less periphery. Predators: raptors, cheetahs etc

39
Q

Depth perception

A

Image to one eye is a little larger than the other, brain understands this as a difference in distance.

Vertebrates 305 (25 decks)

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