the eye - perception Flashcards
(109 cards)
What are the major anatomical components of the eye?
The eye is composed of the cornea, anterior chamber, iris, pupil, lens, vitreous humour, retina, and optic nerve.
What is the function of the cornea?
The cornea is the transparent, curved outer layer that refracts (bends) incoming light to help focus it onto the retina.
What role does the iris play in vision?
The iris, the colored part of the eye, controls the size of the pupil to regulate the amount of light entering the eye.
What is the function of the pupil?
The pupil is the opening in the centre of the iris that allows light to pass into the interior of the eye.
How does the lens contribute to vision?
The lens focuses light onto the retina by changing its shape through a process called accommodation (mediated by the ciliary muscles).
What is accommodation?
Accommodation is the adjustment of the lens’s shape to focus on objects at various distances, achieved by the action of the ciliary muscles.
Diagram – Light Path Through the Eye
[Light] → [Cornea] → [Aqueous Humor] → [Iris/Pupil] → [Lens (Accommodates)] → [Vitreous Humor] → [Retina]
What is the function of the retina?
The retina converts light into neural signals using photoreceptors (rods and cones) and sends this visual information to the brain via the optic nerve.
What are the two main types of photoreceptors in the retina, and what are their roles?
Rods: Detect low light and provide peripheral vision; they do not mediate color vision.
Cones: Function in bright light, enable colour vision, and provide high visual acuity, especially in the fovea.
What is the fovea?
The fovea is the small central region of the retina with a high density of cones, responsible for sharp, detailed central vision
Describe the process of phototransduction in the retina.
In phototransduction, light is absorbed by photopigments (e.g., rhodopsin in rods) in the photoreceptors, triggering a biochemical cascade that leads to hyper-polarisation of the cell and a reduction in neurotransmitter release.
What is the optic nerve, and what is its function?
The optic nerve is a bundle of nerve fibres that carries visual information from the retina to the brain.
What is the blind spot, and why does it occur?
The blind spot is the area on the retina where the optic nerve exits; it lacks photoreceptors, so no image detection occurs there.
What role does the lateral geniculate nucleus (LGN) play in vision?
The LGN, located in the thalamus, acts as a relay station that processes and forwards visual signals from the retina to the primary visual cortex.
How are visual signals processed in the brain after the LGN?
After the LGN, visual signals are transmitted to the primary visual cortex (V1), where further processing such as edge detection, movement, and colour analysis occurs.
How is color vision achieved in the eye?
Colour vision is mediated by three types of cones, each sensitive to different wavelengths (short for blue, medium for green, and long for red), which work together to enable perception of a full spectrum of colours.
What is the difference between scotopic and photopic vision?
Scotopic vision: Low-light vision primarily mediated by rods, which are more sensitive to light but do not detect color.
Photopic vision: Vision under bright conditions primarily mediated by cones, enabling detailed and color-rich perception.
What happens during the process of phototransduction in photoreceptors?
Light absorption by photopigments initiates a biochemical cascade that changes the cell’s membrane potential, leading to reduced neurotransmitter release, thereby encoding the light signal.
Why is the eye considered a complex optical system?
Because it involves multiple refractive surfaces (cornea and lens), dynamic focusing mechanisms (accommodation), and specialized sensory cells (rods and cones) that convert light into neural signals.
What are the three main functions of the lateral geniculate nucleus (LGN)?
Relays visual information from the retina to the primary visual cortex.
Segregates input from each eye into the contralateral hemisphere.
Modulates visual signals via feedback from visual cortex and other areas, refining perception based on attention and context.
What are the three principal classes of LGN cells and their roles?
Magnocellular cells: Fast, myelinated; motion processing (dorsal stream); colour‑insensitive.
Parvocellular cells: Slower, less myelination; form and red–green colour processing (ventral stream).
Koniocellular cells: Small population; blue–yellow colour processing; less well studied.
What occurs at the optic chiasm?
Nasal‑retinal fibres cross to the opposite side so that each hemisphere processes the contralateral visual field (e.g. right visual field → left hemisphere).
Which retinal cells project to the LGN?
Retinal ganglion cells (the final retinal output layer) send axons to the LGN; midget ganglion cells contribute to parvocellular pathways (e.g. yellow–blue discrimination).
What is the primary role of the visual cortex?
To process visual information received from the retina via the lateral geniculate nucleus (LGN), enabling perception of shape, motion, depth, and colour.
