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Biology November exam revision, Transporting substances, Neurotransmission…
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Transporting substances
Smells spread by diffusion. Particles in liquids and gases are constantly moving in random directions.
Diffusion occurs down a concentration gradient. which is the difference in concentration in two areas.
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Active transport is the movement of ions or molecules into higher concentration assisted by enzymes.
The equation to find out percentage change in mass is (Final mass - Initial mass)/Initial mass x 100
Neurotransmission speeds
Motor neurons carry impulses to effectors, effectors include muscles and glands.
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When an impulse reaches an axon terminal a neurotransmitter substance in released into the gap. This is detected by the next neurone and generates an impulse
If you touch something hot and put your finger away straight away this is called reflex. Reflex actions are a response which are automatic and also very quick.
There are neurone pathways called reflex arcs which bypasses the brain that processes information so are quicker.
Parts of the eye
Cones are receptors and are sensitive to the colour of light some cones detect red light were as others detect green and blue light. Cones also generate impulses in scenery neurones which lead the brain through the optic nerve the information from the cones is then transferred into full colour vision at the back of the brain
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The pupil is the dark area in the middle of the eye were light enters. The amount of light coming in is controlled by the muscle the iris which can constrict its diameter or dilate it. Constrict means making it smaller and dilate means making the pupil bigger. Bright light can damage the receptor cells in the retina.
The cornea is the part of the eye which focuses your eye on light. To do this it bends the light rays to bring them together.
The lens is the part of they eye which fine tunes the focusing. The ciliary muscle makes the lens fatter when looking at closer objects and it gets thinner when looking at objects that are further away.