The eye Flashcards
The cornea
What part of the eye is the cornea?
Structure? How does the cornea interact with light?
Functions of the cornea? (2)
The cornea is the outer layer of the eye
It is a transparent wall that refracts (bends) the light passing through it
It protects the eye from any foreign particles as well as protect the entire interior of the eye.
The iris
Where is it located?
What is the opening in the iris?
What is the structure of the iris?
Function? (what does it control? How?)
What does the iris also determine?
What are the two muscles of the iris
located behind the cornea
In the middle of the iris, there is an opening, which is the pupil
The iris is a muscular structure that controls the amount of light entering the pupil, by enlarging or minimizing in size
Muscles of the iris
- Sphincter muscle: a circular muscle that constricts the pupil in bright light,
- Dilator muscle: expands the opening when it contracts
The iris also determines the color of the eye
The iris
Structure?
Function?
What happens when shining a torch on the eye?
What happens when there are low levels of light?
A muscular structure that controls the amount of light entering the pupil by enlarging or minimizing in size.
For example, shining a torch on the eye causes the iris to minimize leading to the pupil decreasing, as the intensity of light is too strong.
However, in a dark room, the iris enlarges, causing the pupil to expand to allow as much light in as possible for vision
The lens
Location?
What is it known as? Why? (What does it do to the different rays of light?)
Where does it focus the light on?
located behind the iris
Known as the convex lens (thicker in the middle and thinner at the edges)
It is referred to as a converging lens because is focuses all the rays of light on one single point, the retina
The retina
Contains what kind of cells?
Functions?
Located at the back of the eye
Contains specialized nerve cells, rods, and cones, photoreceptors that sense light and convert light signals into electrical signals
- Rods are nerve cells sensitive to dim light
- Cones are nerve cells sensitive to bright light
The optic nerve
Connects to?
Function? (transmits sensory information in the form of?)
Which part of the brain processes sensory information? What does this allow?
nerve which connects to the brain
Transmits sensory information in the form of electrical impulses from the eye to the brain
The brain (visual cortex in the occipital lobe) processes the sensory information which allows for vision
Cone cells
Stimulated by what type of light?
Location? Where is the highest concentration of cone cells?
What are the three types of cone cells? Which cone cell is the most abundant?
What are the two parts of the retina? where are they and what are they responsible for?
What do cones contain? specifically?
What are opsin amino acids sensitive to?
What type of vision do cone cells allow?
Stimulated by light
Located in the macula and concentrated in the fovea (center of the macula) enables people to see the fine details.
Also located in the peripheral retina
The retina is made up of two parts:
Macula (at the center of the retina- direct vision)
Peripheral retina (fills in vision on the edges of sight- peripheral vision)
Three types of cone cells
- red cone cells (most abundant)
- green cone cells
- blue cone cells
Cones contain colour-sensitive photopigments namely opsin amino acids, that are sensitive to different wavelengths of visible light (allowing colour vision)
What are the two types of photoreceptor cells in the retina?
What are they responsible for? How?
Rods and cones
Responsible for the sense of sight by converting light signals into electrical signals for the visual cortex of the brain to decode (produce sight)
What is the macula?
What vision does it process?
The macula is the centre of the retina that processes, sharp, clear, and direct vision
Cone cells
What do cone cells contain?
What are they sensitive to?
What are the three types of cones?
Do cones only respond to their specific wavelength?
What do wavelengths stimulate? produce?
Cone cells contain colour-sensitive photo-pigments, specifically, ospin amino acids. which are sensitive to different wavelengths of visible light
Red, green, and blue cones
Although cones mainly respond to light in their own colour zone (region of colour spectrum) cones can overlap. Therefore cones not only respond to their own specific wavelength but also a variety of wavelengths.
- Wavelengths can stimulate more than one cone cell to produce colour vision
Cone cells
What initiates the activation of a cone cell?
Activation for red and green cone cells? units?
What colour does the brain perceive when cone cells are equally activated?
Therefore, what do cone cells enable? wny?
Activation of each cone cell depends on their relative levels of activation
For instance, the activation level for red and green cones is around 580 nm (Nanometer)
When cone cells are stimulated equally, the brain perceives the colour as white
However, if cone cells are being activated in accordance with their activation levels, the colour perceived by the brain is specific to the wavelength. Therefore activation levels of cone cells enable the distinction of clours
Rods and cones
Which is more sensitive to light?
Where do they function most efficiently?
What type of cells are rods and cones?
Rods are more sensitive to light than cones
Rods function better in lower/dim light levels
Cones function better in bright light
Rods and cones are specialized light-sensitive photoreceptor nerve cells
What are bipolar cells?
Bipolar cells are interconnector neurons which connect rods and cones
