THE EYE
Sclerotic layer/ Sclera
-outermost layer; tough, white, tissues
-support framework of the eye + protection

Choroid
-2nd/ middle layer; black due to melanin in tissue, richly supplied w/ capillaries
-absorb light (prevent reflection) + provide O₂ + nutrients

Retina
-3rd/ inner-most layer; contains 2 photoreceptor cells: rods-long, thin + cones-wider. lens focuses light onto retina
-light-sensitive cells relay images, through nerve fibres, to brain for interpretation
iodopsine-pigment in cones: viewing in bright light + of colours
rhodopsin-pigment in rods: allows in dim light + of white light, bright light > rhodopsin bleached

Yellow spot/ Fovea centralis
-small depression in retina
-made of cones only, most sensitive part of retina: sharpest vision

Blind spot
-on retina where optic nerve leaves eye; has no light-sensitive cells
-no light-sensitive cells > no info. of image to be sent to brain > part of retina of no vision

Optic nerve
-made of nervous tissues
-picks up nervous impulses from photoreceptors > sends to brain for interpretation

Cornea
-part of sclera; transparent, curved
-allows light to enter eye, refracts light to lens (largest amount of refraction)

Conjuctiva
-thin epithelium; lines insides of eyelids, front of sclera + cornea
-protects the eye from dust + foreign bodies

Iris
-continuation of choroid; contains radial + circular muscles
-muscles control size of pupil (amount of light entering the eye)

Pupil
-aperture in centre of iris
-allows light to enter the eye (black due to choroid: absorbs light)

Ciliary muscles/ body
-extension of choroid; connected to lens by fibres
-fibres allow it to change shape of lens + hold lens in place

Suspensory ligaments
-tough fibres
-fibres allow it to change shape of lens + hold lens in place

Lens
-transparent, elastic, bi-concave, crystalline structure
-refracts and transmits light to retina (separates eye into 2 chambers)

Aqueoues + Vitreous humour
-AH-watery fluid in anterior chamber, VH-jelly-like fluid in posterior chamber
-keep pressure constant > maintain eye’s shape + allow light to be transmitted + provide nutrients to lens & conjuctiva (refraction of light)

Nervous System
Chemical Control of Plant Growth
The Use and Abuse of Drugs
Diversity of Organisms
Nutrient cycles and Ecology
Parasitism
The Human Impact on the Environment
Reproduction in plants
Sexual reproduction in animals
Genetics
Cell Structure and Organisation
Enzymes
Nutrition
Transport in Plants
Support, Movement and Locomotion
Transport system in man-circulatory system
Respiration
Excretion
Homeostasis

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