Biology 5.1.5 Flashcards
The Eye is a ___ Organ.
Sense.
What are ‘Receptors’?
Receptors are Groups of Specialised Cells that can Generate an Electrical Impulse in a Sensory Neurone.
The Eye contains 2 types of Receptor Cells. What are these, and what do they do? (2)
-Rod Cells: Sensitive to Light Intensity.
-Cone Cells: Sensitive to different Wavelengths of Visible Light (Colour).
Where are the Rod & Cone Cells in the Eye Located?
Retina.
What is the Function of the Cornea?
Transparent Lens that Refracts Light as it Enters the Eye.
What is the Function of the Iris?
Controls how much Light Enters the Pupil.
What is the Function of the Lens?
Transparent Disc that can Change Shape to Focus Light onto the Retina.
What is the Function of the Retina?
Contains Light Receptor Cells- Rods, & Colour Detecting Cells- Cones.
What is the Function of the Optic Nerve?
Sensory Neurone that Carries Impulses between the Eye & the Brain.
What is the Function of the Pupil?
Hole that allows Light to Enter the Eye.
Why does the ‘Pupil Reflex Action’ Occur?
To Protect the Retina from Damage in Bright Light, & Protect us from not Seeing Objects in Dim Light.
The Pupil Reflex Action is Controlled by 2 Groups of Muscle. These are: (2)
-The Radial Muscle.
-The Circular Muscle.
In Dim Light, the Pupils ___, in order to allow as much Light into the Eyes as possible.
Dilate.
In Bright Light, the Pupils ___, in order to Prevent too much Light Entering the Eye & Damaging the Retina.
Constricts.
What is ‘Accommodation’?
Accommodation is the Process of Changing the Shape of the Lens to Focus on Near or Distant Objects.
To Focus on a Near Object: (3)
-The Ciliary Muscles Contract.
-The Suspensory Ligaments Loosen.
-The Lens is then Thicker, & Refracts Light Rays more Strongly.
To Focus on a Distant Object: (3)
-The Ciliary Muscles Relax.
-The Suspensory Ligaments are Pulled Tight.
-The Lens is then Pulled Thin, & only Slightly Refracts Light Rays.
What are 2 Common Defects of the Eyes? (2)
-Myopia: Short-Sightedness.
-Hyperopia: Long-Sightedness.
How can we easily Treat Common Eye Defects?
With Glasses / Contact Lenses.
What Happens if you have ‘Myopia’? (3)
-Lens is too Thick & Curved.
-Eyeball is too Elongated.
-Image is in Focus in Front of the Retina.
What type of Lens can Correct Myopia?
Concave Lens.
What Happens if you have ‘Hyperopia’? (3)
-Lens is too Thin & Not Curved enough.
-Eyeball is too Short.
-Image is in Focus Behind of the Retina.
What Type of Lens can Correct Hyperopia?
Convex Lens.
Explain how the Eye Detects Light: (5)
-Light Rays Pass Through the Transparent Front of the Eye. This is Called the ‘Cornea’. The job of the Cornea is to Start the Focussing of the Light Rays.
-The Light Rays then Pass Through the ‘Pupil’, in the Centre of the ‘Iris’. The Iris is the Coloured Part of the Eye.
-The Light Rays now Pass Through the ‘Lens’. The job of the Lens is to Focus the Light Rays Onto the Back of the Eye (the ‘Retina’). One Key Feature of the Lens is that it can Change its Shape, Allowing us to Focus on Distant or Near Objects (Accommodation).
-The Light Rays are now Focussed Onto the Back of the Eye, Called the ‘Retina’. The Retina Contains Receptor Cells for Light (‘Rod Cells’), & Receptor Cells for Colour (‘Cone Cells’).
-The Receptor Cells in the Retina now Send Electrical Impulses Down the Optic Nerve, to the Brain.
