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Slide 1

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KEY WORDS
· AXON: The part of a neurone the carries
impulses away from its cell body.
· DENDRON: The part of a neurone the carries
impulses towards its cell body.
· DENDRITES: Small dendrons that link
neurones to the CNS.…read more

Slide 2

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NERVES
· There are three types of nerves:
· SENSORY NEURONE: Carries impulses from receptor
cells (also called TRANDUCERS) towards the CNS.
Has a small cell body with a long axon and dendron
either side.
· MOTOR NEURONE: Carries impulses from the CNS
to EFFECTOR CELLS (which carry out the desired
action). Has a large cell body with a long axon and
many small dendrons called dendrites.
· RELAY NEURONES: Carries impulses between other
neurones.…read more

Slide 3

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A MOTOR NEURONE…read more

Slide 4

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A SENSORY NEURONE…read more

Slide 5

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RESTING POTENTIAL
· When a neurone is at rest it has a potential
difference across it (-70mV), this is called the
resting potential.
· This is brought about by sodium/potassium ion
pumps in the cell membrane of the axon/dendrons.
· They pump three sodium ions out for every two
potassium ions in, hence there are more positive
charges on the outside, so the inside of the cell is
negatively charged with respect to the outside.…read more

Slide 6

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ACTION POTENTIAL
· An action potential is the `impulse' carried by
neurones.
· It starts in the GENERATOR REGION of RECEPTOR
CELLS (TRANSDUCERS) when they detect a change
in energy (e.g. pressure/light).
· This causes sodium ion channels to open and
sodium ions diffuse into the cell, raising the
potential difference across the membrane.
· If the potential difference rises above the
THRESHOLD POTENTIAL, an action potential will
occur.…read more

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