Eyes Flashcards
(22 cards)
What are sense organs?
Groups of receptor cells which respond to specific stimuli such as light, sound, touch, temperature, and chemicals.
What happens when a receptor cell in a sense organ is stimulated?
It generates an electrical impulse.
What is the role of sensory neurones?
They carry the impulse to the central nervous system.
What is the pathway of an impulse from the sensory neurone to the effector?
Sensory neurone → central nervous system → relay neurone → motor neurone → effector.
What are the main parts of the eye?
- Cornea
- Iris
- Pupil
- Lens
- Ciliary muscles
- Suspensory ligaments
- Retina
- Fovea/yellow spot
- Optic nerve
- Blind spot
What is the function of the cornea?
It is transparent and refracts light rays into the pupil.
What is the iris and its function?
The coloured part of the eye that controls how much light enters the pupil.
What does the pupil do?
It allows light to enter the eye and its size changes to control light entry.
What is the function of the lens in the eye?
It focuses light onto the retina.
What do ciliary muscles and suspensory ligaments do?
They control the shape and thickness of the lens.
What are photoreceptors and their types?
- Rods: Vision in dim light
- Cones: Bright light and colour vision
What is the fovea/yellow spot?
The most sensitive area of the retina with the greatest density of light receptors.
What is the function of the optic nerve?
Transmits impulses from the eye to the brain.
What is the blind spot?
A region of the retina without photoreceptors, not sensitive to light.
What is the pupil reflex?
A reflex action to protect the retina from damage in bright light and improve vision in dim light.
What happens to the pupil in dim light?
The pupil dilates to allow more light to enter.
What happens to the pupil in bright light?
The pupil constricts to allow less light to enter.
What is accommodation in the eye?
The adjustment of the lens to focus on objects at different distances.
What occurs when focusing on a near object?
- Ciliary muscles contract
- Suspensory ligaments slacken
- Lens becomes thicker and more convex
What occurs when focusing on a distant object?
- Ciliary muscles relax
- Suspensory ligaments tighten
- Lens becomes thinner and less convex
Fill in the blank: The retina contains light-sensitive cells called _______.
photoreceptors
True or False: The iris contains only one set of muscles.
False
