Lecture 8, 9 and 10 Flashcards
What do flat-sheet eyes contain? What do these eyes provide?
What does the pigment layer contain and what does this do?
A layer of photoreceptor cells that form a primitive retina
Some sense of light direction and contrast
Contains shading pigment to that helps provide directional information by shading light coding from some directions
What is the retina like in cup-shaped eyes?
This folded to form a narrow aperture
What is the lens like in a vesicular eye? What does this mean? What can the lens often do?
The lens is inserted into the pinhole aperture.
It collects light from multiple sources and refracts it, thereby focusing it into the retina.
. Often the lens is able to change shape, thereby allowing to focus objects
In convex eyes where can the photoreceptors radiate outwards?what does this form?
Radiate outwards from the base, forming a convex rather than a concave, light-gathering surface
What is a single unit of a compound eye called?
Ommatidium
Describe how apposition compound eyes work
The ommatidia are surrounded by a pigment cell. Each ommatidia operates independently as detects a small part of the environment directly in front of the ommatidium
Describe how superposition compound eyes work and what thy are found in
May ommatidia work together to produce a bright, superimposed image. Those eyes are found in nocturnal insects
What does light entering the light pass before striking the retina?
Passes through the cores, the aqueous humour, the pupil, the lens m, and the vitreous humour before striking the retina
What is the fovea? What does it provide?
Is a pit in the retina which provides the clearest vision
What is the choroid?
The vascular layer of the eye (supporting the retina with blood- supply oxygen, energy etc.)
Where are the focal receptor cells located?
In the retina
Need to see pages 34/35 about eyes- couldn’t make flashcards about them
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Where are the photoreceptors (Ross and cones) locates?
In the deepest layer of the retina (far away from the light)
What does the retina consist of in cephalopods? How does light strike the photoreceptors?
Retina consists of a layer of photoreceptor cells and supporting cells. Light strikes the photoreceptors directly, without passing through multiple layers
Why is there little to no signal processing in the retina of cephalopods?
Because there are no interneurons
How did the eye of the cephalopod evolve?
Independently of the vertebrate eye
Describe rod photoreceptor cells
Contain many photopigments and are therefore very sensitive. They are active under dim light (not during the day). Ross cannot discriminate colours.
Describe come photoreceptors
Contain less photopigments than Ross and operate during the day. They are able to detect different colours (wavelength of light)
Where is rhodopsin located?
Within the membrane disks of the photoreceptors (rods)
When are vertebrate photoreceptor cells (not invertebrates) depolarised?
When they are unstimulated
What does stimulation of the vertebrate photoreceptor do?
Causes hyperpolarisation
What do photoreceptor cells release when in the dark?
Transmitters (glutamate)
What do touch receptors in Caenorhabditis elegant contain?
Mechanosensott neurons with ENaC (epithelial sodium channel) type channels in their membrane