The Eye Flashcards
What is the sclera
Tough outer coat. Visible white part of the eye.
What is the choroid layer
Middle layer of eyeball. Deeply pigmented to absorb light and prevent internal reflection. Contains lots of blood vessels.
What is the retina
Innermost layer in eye. Contains many rods and cones + fibre nerves.
What is the optic nerve
Carries nerve impulses from the retina directly.
What is the fovea (yellow spot)
Part of the retina where cones are concentrated these enables us to see colours in bright light
What is the conjunctiva
Transparent layer the protects cornea
What is the cornea
Transparent window at front of eye. Allows light to pass through
What is the iris
Coloured ring of tissue behind cornea. Controls amount of light entering the eye by changing size of pupil.
What is the pupil
Hole in centre of iris - size is controlled by radial and circular muscles of iris
What is the ciliary body/ciliary muscle
Contains muscles which can contact or relax to change thickness of lens
What is the suspensory ligament
Hold lens in position
What is the lens
Clear part behind the iris that helps to focus light onto the retina. Helps to focus on far and close objects
The retina consists of _________ and _________
Rods and cones
________ see in dim light
Rods see in dim light
________ see in bright light
Cones
________ see black and white vision while _________ see colour
Rods Cones
_________ are found throughout the retina
Rods
___________ are concentrated in the yellow spot
Cones
What are the 2 types of muscle around the iris
Circular and Radial
When the circular muscle contracts, the pupil gets _____________
Smaller
When the radial muscle contracts, the pupil gets ____________
Bigger
Name the stimulus that enters the eye and is detected by receptors
Light
Which part of the eye contains receptors
Retina
How do messages travel from receptors in the eye to the brain
By nerve impulses. Receptor —> Along a sensory neuron (optic nerve)
Name 3 sense organs
Tongue, Nose, Ears
The _________ consists of circular and radial muscles
Iris
The __________ consists of millions of light sensitive cells
Retina
The ____________ consists of many blood vessels
Choroid
The _________ contains only cones
Yellow spot / Fovea
The blind spot has no _________-sensitive cells
Light-sensitive cells
The ligaments hold the _______
Lens
The __________ allows light to enter the eye
Pupil
The __________ bends the light rays
Cornea
The lens can change __________
Shape
The optic nerve sends messages to the __________
Brain
The rods respond to _______ light
Dim light
The cones respond to __________ light
Bright light
In bright light the pupil becomes ___________
Smaller
In bright light the __________ muscles relax and the ____________ muscles contract - thus the pupil becomes ___________
Radial
Relax
Circular
Contracts
Smaller
If it is bright, then the pupil becoming smaller allows ________ light to fall on the ___________ at the back of the eye
Less Retina
What is the job of the iris
Controls the amount of light that falls in the retina
Flow diagram to summarise the stages in a spinal reflex
Stimulus —> receptor —> sensory neurone —> relay neuron —> motor neuron —> effector
1
Suspensory Ligament
2
Conjunctiva
3
Iris
4
Pupil
5
Cornea
6
Ciliary muscle
7
Lens
8
Retina
9
Fovea
10
Optic nerve
A person moves from a dim room into bright sunshine. Describe the change in the appearence of their pupils.
Their pupils contract to allow less light into the eye
In the dark you cannot see colours… Why?
Because in the dark our eyes only use rods which don’t see colours. Cones don’t respond to dim light therefore they aren’t used.
