The Eye Nervous System Flashcards
Function of cornea.
The transparent lens that refracts light as it enters the eye.
Function of iris.
Controls how much light enters the pupil.
Function of lens.
The transparent disc that can change shape to focus light onto the retina.
Function of the pupil.
The hole that allows light to enter the eye.
Function of the retina.
Contains light receptor cells (rods which detect light intensity and cones which detect colour)
Function of the optic nerve.
A sensory neurone that carries impulses between the eye and the brain.
What happens to the radial muscles when there is dark light/ bright light?
Dark light= contracted
Bright light= relaxed
What happens to the circular muscles when in dark light/ bright light?
Dark light= relaxed
Bright light= contracted
What happens to the pupil size in dark light/ bright light?
Dark light= wide
Bright light= narrow
Definition of accommodation
The process of changing the shape of the lens to focus on near or distant objects
What happens to -ciliary muscles - suspensory ligaments -lens When an object is close by?
- ciliary muscles: contracted
- suspensory ligaments: slack
- lens: fatter
What happens to - ciliary muscles - suspensory ligaments - lens When an object is far away?
- ciliary muscles: relaxed
- suspensory ligaments: pulled tight
- lens: thinner
How does refraction of light change when an object is close by/ far away?
Close by: refraction of light increases.
Far away: refraction of light is less.
How do the light rays change when an object is close by/ far away?
Close by: light rays are diverging
Far away: light rays are parallel.
Definition of myopia (short sightedness)
You can see objects at a short distance away, but struggle to see objects at a distance.
Why does myopia occur?
The eyeball is too long for the strength of the lens
The cornea is too sharply curved.
When the eye attempts to produce and image, it falls short of the retina.
How can you correct myopia?
Myopia can be corrected by a concave lens which diverges the light rays before they reach/enter the eye.
Definition of hyperopia (long sightedness)
You can see objects at long distances away, but struggle to see near objects.
When does hyperopia happen?
It happens when the lens is too weak because it is not thick enough.
When the eyeball is too short.
The cornea is not curved enough.
When the eye attempts to produce an image, it falls behind the retina.
How can hyperopia be corrected?
It can be corrected by a x lens which converges the light rays before they reach/ enter the eye.
