Lecture 5 (Visual Sensing)

Question 1

What does colour vision requires?

Answer 1

Photoreceptors detecting alternative wavelengths, an optical system capable of providing an image, and a nervous systems for decoding the image.

Question 2

What are the two main photoreceptor cells in vertebrate retina?

Answer 2

Rods and cones

Question 3

What do rods do?

Answer 3

Sensitive to dim light responsible for scotopic vision(night)

Question 4

What visual pigments are present in rods?

Answer 4

Rhodopsin, consisting of opsin bound to 11-cis-retinal chromophore.

Question 5

What is adaptation in rods?

Answer 5

Dynamic changes to light sensitivity

Question 6

How does this interact with light?

Answer 6

Photon absorption causes isomeriation from cis to trans form, initiation CC and signalling cascades.

Question 7

What is the process of this signalling cascade?

Answer 7

transducin activation which activates phosphodiesterase, this following hydrolysis leads to closure of channels in plasma membrane which leads to neurotransmittter release into neurons.

Question 8

What do cones do?

Answer 8

Less sensitive, providing colour vision and best for photopic vision(light)

Question 9

What are the types of cones?

Answer 9

Opsins sensing short, middle, and long wavelengths, that being blue, green, and red respectively.

Question 10

How does the brain perceive light following this?

Answer 10

Signals from rods and cones transmitted to bipolar cells and then ganglion cells, send signals to brain via optic nerve.

Question 11

How does the retina process visual information?

Answer 11

Neural circuits like lateral inhibition and convergence/divergence signals, extracting contrast, motion, and spatial patterns.

Question 12

What is lateral inhibition?

Answer 12

Capacity of excited neurons to reduce activity of their neighbours

Question 13

What is the absorption spectra?

Answer 13

Describes wavelength of light absorbed by a pigment molecule.

Question 14

Why is this important for colour vision?

Answer 14

Insight into spectral sensitvity of photoreceptor cells, that being with WL are most effective for stimulating responses.

Question 15

What is action spectra?

Answer 15

Measurements of effectiveness of different wavelengths of light producing biological responses.

Question 16

How is action spectra relevant to vertebrate eyes?

Answer 16

Provides basis of how visual systems percieve hues and colours.

Question 17

What is the biochemical basis of action spectra?

Answer 17

Chemical properties of chromophores and structural features of opsin proteins influencing pigment (opsins) absorption properties.

Question 18

How does this change for animals who perceive UV?

Answer 18

UV (300-400nm)-senstivie photoreceptor cells (either cones or rods)

Question 19

What are examples?

Answer 19

Birds and reptiles with SWS1 opsin enabling UV detection, like the European robin.

Question 20

Why is this evolutionary important?

Answer 20

UV-based foraging strategies in insects, UV-reflective signalling patterns in flowers for pollinator attraction.

Question 21

How are these retina developed to UV-sensitization?

Answer 21

Morphological differences in synaptic ribbon density, and synaptic contacts with bipolar and ganglion cells, contribution to efficient capture/processing of UV information.

Question 22

How are flowers adapted to UV attraction?

Answer 22

Common rock rose has a bull’s eye pattern consisting of UV reflective rings.

Question 23

How do flowers do this?

Answer 23

UV-absorbing compounds like flavonoids and anthocyanins, serving as visual guides for bees.

Question 24

What is an example of the importance of colour contrast in wavelength sensitivity?

Answer 24

Bird plumage is an indicator for mate choice in birds, Blue tits for example prefer males with high color contrast between plumage patches.

Question 25

How is this important in pollinator attraction?

Answer 25

Bee orchid mimics female bees, including body shape, coloration, and texture.

Question 26

How is color contrast important here?

Answer 26

A yellowish-green background color provides a contrasting backdrop for darker markings mimicing body and wing patterns of female bees.

Question 27

How is UV used?

Answer 27

Flowers exhibit UV-reflective patterns, mimicking UV-reflectance of female bee cuticles or wings

Question 28

What influence does this have on ecology?

Answer 28

Male bees are attracted, inadvertently come into contact with reproductive structures of the plant.

Question 29

Whats an example of plant response to UV light?

Answer 29

Flavonoid production

Question 30

What are flavonoids?

Answer 30

Secondary metabolites synthesised in response to UV radiation.

Question 31

What are their functions?

Answer 31

UV protection, herbivore/pathogen defense, attraction of pollinators.

Question 32

How do they protect against UV?

Answer 32

Pigmentation absorbing UV-B, protecting against DNA damage and oxidative stress

Question 33

How do they act in defense?

Answer 33

They deter herbivores by acting as feding deterrants, thus the indirect presence of Flavonoids by UV impact herbivores of higher trophic levels, as well as those animals consuming herbivores rich in flavonoids.