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20 Cards in this Set
- Front
- Back
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What is the cornea?
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Front part of the tough outer coat, the sclera. It is convex and transparent. It refracts light-bends it as it enters the eye
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What is the iris?
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Pigmented, decides colour of eyes so light cannot pass through it, its muscles contract and relax to alter the size of its central hole or pupil.
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What is the lens?
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Transparent, bi-convex, flexible disc behind the iris attached at the suspensory ligaments to the ciliary muscles. Focuses light onto the retina
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What is the retina?
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The lining of the back of the eye containing two types of photoreceptor cells - rods - sensitive to dim light and black and white, cones - sensitive to colour. A small area called the fovea in the middle of the retina has many more cones than rods.
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What is the optic nerve?
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Bundle of sensory neurones at back of eye. Carries impulses from the eye to the brain.
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What is binocular vision?
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Because our eyes sit side by side, each eye captures a slightly different view
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Why is it good for birds and lizards to have monocular vision?
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Their eyes are on each side of their head, giving them a greater field of view, which is useful for spotting predators.
However they have poor depth perception |
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Why do some people have short-sight?
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Their lens focuses the sharpest image in front of the retina instead of on it
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What is long-sight?
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Their lens focuses the sharpest image behind it, instead of on it.
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What causes colour blindness?
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It is inherited, people with colour blindness have a lack of receptors, or defects in them.
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How do nerve cells carry information?
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By tiny electrical signals
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What is the job of sensory neurones?
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They carry signals from receptors to the spinal cord and brain.
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What is the job of relay neurones?
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They carry messages from one part of the central nervous system to another
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What is the job of motor neurones?
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They carry signals from the CNS to effectors
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What happens in synapses?
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Where two neurones meet, there is a tiny gap called synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the neurone transmit an electrical signal.
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What happens when a receptor is stimulated?
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The receptor sends a signal to the central nervous system, where the brain co-ordinates the response.
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What is an example of an effector?
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A muscle contracting
A gland releasing a hormone or another chemical |
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What happens with reflex actions?
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Receptor detects a change in the environment➡️sensory neurone sends signal to relay neurone➡️motor neurone sends signal to effector➡️effector produces a response
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What do stimulant drugs do?
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•Cause more neurotransmitter molecules to diffuse across the synapse
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What do depressants do?
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Slows down brain activity, stop the next neurone sending nerve impulses - they bind to the receptor molecules it needs to respond to the neurotransmitter molecules.
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