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AQA Unit 5 Biology
Frihah Parvaiz

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Nerve cells electrical impulses along their length. They stimulate target cells by secreting
chemical neurotransmitters directly on to them. This results in rapid, short-lived and localised

Mammalian are that stimulate their target cells via
blood This results in slow, long-lasting and

The hormonal system consists of glands (group of cells…

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Histamine and are local chemical
some mammalian cells and affect only cells in their immediate vicinity.

...are released from cells and only affect cells in immediate
Usually released by injured cells.
Ssecretion causes blood vessels around the area to dilate

Produced by mast cells in…

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In flowering plants, specific growth factors diffuse from growing regions other They regulate growth
in to directional stimuli. role of indoleacetic acid in controlling tropisms in flowering

The auxin causes The auxin causes increased
decreased growth in growth in the lower side
the lower side of the of the shoot…

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The structure of a myelinated motor

Myelinated motor neurone


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The of a resting potential in terms of differential permeability,
electrochemical gradients and the of sodium

Distribution of ions at resting potential

When there is no nerve impulse the membrane potential of an axon
is called `resting potential'. The inside of the axon is -70Mv. Due to
this difference in…

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in permeability lead to and the
generation of an action potential. The all-or-nothing

The action potential

The term `action' potential and
`resting' potential can be misleading
because the movement of sodium ions
inwards during the action potential is
due to diffusion and resting potential is
maintained by active transport.


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The nature and of the refractory period in producing impulses.

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Factors affecting the of myelination axon diameter;
The of an action potential along and axons, resulting in nerve


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The detailed structure of a and of a neuromuscular

Candidates should be able to explain
· unidirectionality
· temporal and spatial summation inhibition.

Structure of a synapse





This set of notes covers the transmission of nervous implulses and sums up information in useful flow diagrams, images showing the sequence of events, and concise text. One page unfortunately  seems to have suffered in the uploading process but nevertheless this is a very good resource to use as a basis for revision.




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