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Eye.SAHB
| Question | Answer |
|---|---|
| Cornea definition: | Transparent layer, does most of the refraction of light rays from an object. Forms an inverted and smaller image on the retina |
| Aqueous humour: | Keeps the cornea bent through turgor pressure |
| Pupil: | Circular opening which allows light into the eye Black because choroid is visible through it. |
| Iris definition: | "Coloured" part of eye. This part expands or contracts to control light going into the eye by reflex action |
| What happens to the radial muscles under low light intensity and why? (Pupil reflex 1) | Radial muscles of Iris contract and pupil is opened wider so more light may enter |
| What happens to the radial muscles under high light intensity and why? | Circular muscles of iris contract to reduce pupil size so that less light may enter. This is done to protect the Retina from bleaching |
| What type of muscles are the radial and circular muscles? | Antagonistic - They have opposing actions (Radial muscle is RADICAL, wants to allow more light in, lives life dangerously) (Circular muscle is too fat, I mean circular, to do fun stuff like the radical radial muscle) |
| Retina: | Contains light sensitive cells (The RODS and COANS) light at this layer will produce an inverted, smaller image. |
| Fovea (yellow spot) definition: | Greatest density of cones and offers maximum sharpness but only works efficiently in bright light. |
| Optic nerve: | Sensory neurones that carry nervous (electrical) impulses to the visual centre at the rear of the brain |
| Blind spot definition: | In front of the exit point of the optic nerve. No light-sensitive nerves here so no light is detected here |
| Accommodation definition: | The production of a finely focused image on the Retina. Carried out by the CILIARY MUSCLES. |
| What happens to the ciliary muscles, suspensory ligament and lens when a close object is looked at? | Ciliary muscles contract, pulling eye inwards, suspensory ligaments slacken, lens becomes short and fat. (Lens must be round to greatly refract) |
| What happens to the ciliary muscles, suspensory ligament and lens when a distant object is looked at? | Ciliary muscles relax, eye-ball is spherical once more, ligaments tighten and the lens becomes long and thin (Lens must not be round as it needn't refract greatly) |
| Rods: | Provide black and white images, provide great sensitivity at low light as many rods may be wired to a single sensory neurone. (Images lack detail because of this as well) |
| Cones: | Provide detailed images, but only under high light intensity (their single connections to the optic nerve make them insensitive) |
| What are the three types of cone? | Cones that detect red light, cones that detect green light and cones that detect blue light |
| Layer of pigment: | Prevents total internal reflection (prevents multiple or blurred images) |
Created by:
sibbles101
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