B3.1 The Nervous System - Eye Flashcards
Describe and state the function of the cornea.
- Transparent coating on the front of the eye
- Protects the eye, refects light entering the eye
Describe and state the function of the conjunctiva.
- Protective membrane contiunuous with the eyelids across the front of the visible sclera
- Protects from infection by stopping pathogens entering the eye
Describe and state the function of the pupil.
- Central hole in the iris
- Allows light to enter the eye
Describe and state the function of the iris.
- Coloured ring of muscle
- Alters pupil size by contracting or relaxing
Describe and state the function of the lens.
- Transparent biconvex lens
- Focuses light clearly onto the retina
Describe and state the function of the suspensory ligaments.
- Work together with the cilary body to control the shape of the lens by becoming taught or slack
- Connect the ciliary body to the lens
- When ciliary muscles contract the suspensory ligaments relax allowing the lens to go fat
- When ciliary muscles relax the suspensory ligaments are pulled taught stretching the lens thinner
Describe and state the function of the retina.
- Contains two types of photoreceptor cells rods and cones
- Photoreceptor cells produce a nervous impulse when exposed to light
Describe and state the function of the optic nerve.
- Nervous tissue
- Carries nerve impulse from the retina to the brain
Label the parts of the eye
- Sclera – Tough outer wall, ‘white’
- Conjunctiva – membrane over eye
- Cornea – transparent outer layer
- Lens – focuses light
- Pupil – allows light into eye
- Aqueous humor - nutrients & pressure
- Iris – controls diameter of pupil via circular and radial muscles
- Vitreous humor – pressure and shape.
- Choroid – nutrients & waste
- Fovea – blind spot
- Optic nerve head – nerves exit
- Optic nerve – impulses to eye
- Retina – contains rods & cones
What is the aqueous humor
A fluid which is between the cornea and lens that provides nutrients for the the lens and cornea that have no blood supply and helps maintain pressure
What is the vitreous humor?
A transparent, colourless, gel-like substance that fills the space between the lens and the retina within the eye and helps maintain pressure and shape.
Name the two types of photo receptor cell in the eye.
- Rods - respond to light and allow you to see in low light levels
- Cones - respond to red, blue and green light to allow you to see in different colours
Name the cells and their structures.
Cell A: Rod cell
Cell B: Cone cell
- Outer segment
- Inner segment
- Synaptic region
- Disc
- Connecting cillium
- Mitochondria
- Nucleus
- Synapse
How do the circular and radial muscles control the size of the pupil?
- In dim light the radial muscles contract and the circular muscles relax to make the pupil become larger to allow more light to reach the retina.
- In bright light the radial muscles relax and the circular muscles contract to make the pupil become smaller and protect the retina.
How do the suspensory ligaments and cilliary muscles control the shape of the lens?
- When an object is nearby the cilliary muscle contracts down towards the lens allowing the suspensory muscles to become slack. This causes the lens to fatten and become more convex, increasing the refraction of the light passing through.
- When an object is far the cilliary muscle relaxes away from the lens allowing the pulling the suspensory muscles taut. This causes the lens to be pulled thiner and become less convex, decreasing the refraction of the light passing through.
What is meant by the term myopia?
- Shortsightedness
- Someone who is short-sighted can see near objects clearly, but they cannot focus properly on distant objects.
What is meant by the term hyperopia?
- Longsightedness
- Someone who is long-sighted can see distant objects clearly, but they cannot focus properly on near objects.
