Vertebrates 19 - Vision Flashcards Preview

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Flashcards in Vertebrates 19 - Vision Deck (39)
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1

Median eyes

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

2

Pineal glad

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

3

Melatonin

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

4

Image forming eyes

Real eyes. Durr.

5

Sclera

Outer layer, white part. Holds everything else in.

6

Coroid layer

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

7

Tapetum lucidum

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.

8

Fovea

Highest concentration of photoreceptors

9

Optic disk

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

10

Vitreous humour

Supports lens and retina.

11

Aqueous humour

B/w cornea and lens.

12

Cornea

Allows light to pass through

13

Lens

Focuses light onto the retina.

14

Ciliary body

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

15

Iris

Control amount of light entering eye through pupil.

16

Pupil shapes

Goats/sheep - horizontal; snakes, cats - vertical

17

Eyelid

Skin for protecting the eye

18

Nictitating membrane

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

19

Retina

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

20

Retinal pathway

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

Superior colliculus

Coordinates motor movements of eyes. Connected to the thalamus.

22

Photoreceptors in the eye

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

Membrane disks.

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

24

Rods

high sensitivity, low acuity, 400-600nm

25

Cones

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

26

Cone types

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

27

Tetrachromats

Have 4 cones. Birds and lizards

28

Dichromats

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

29

Trichromats

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

30

Evolution of mammals and vision

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