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Slide 1

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(Action potentials) By Daniella Di-Fonzo…read more

Slide 2

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Motor neurone
neurone Intermediate
Cell body in spinal Cell bodies in Call body and
cord, axon runs to dorsal root cytoplasmic process
anywhere in your ganglia, just located in spinal cord
body, e.g., toe.…read more

Slide 3

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A Reflex Arc
· Pathway in which impulses are
carried from a receptor to an
· Muscles and glands are effectors
· The impulse arrives at the
sensory neurone and passes
through dorsal root ganglion
into the spinal cord
· May be passed straight to a
motor neurone or to an
intermediate neurone then the
motor neurone.
· Arrives at effector in less than
one second of the receptor
picking up the stimulus.
· This is a reflex action (a fast
stereotyped response to a
particular stimulus) and allows
us to respond to potential…read more

Slide 4

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Structure of a nerve
· Axons of neurones are usually found in
· The bundle may be surrounded by a
protective covering called perineum
· Depending on the neurone that makes up
the bundle, these are either called motor
nerves, sensory nerves or mixed nerves.…read more

Slide 5

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Neurone cell membranes are
polarised at rest
When a neurone isn't being stimulated (at
rest) the outside of the cell is more positively
charged than the inside of the cell because
there are more positive ions outside the cell.
The Membrane is polarised as there is a
difference in voltage across it. At rest this is
about -70mV and is known as resting
The resting potential is created and
maintained by Sodium- Potassium pumps and
Potassium ion channels in the neurones
membrane.…read more

Slide 6

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Outside cell
The Sodium 3Na Potassium ion
potassium pump + channels allow
uses active facilitated
transport to move diffusion of
three sodium ions potassium ions
out of the neurone out of the
for every two 2K neurone, down
potassium ions + their
moved in, this Inside cell concentration
requires ATP. gradient.
· The sodium- potassium pumps move sodium ion s out of the
neurone and the cant diffuse back in as the membrane is
impermeable to Na+ ions. This creates a Sodium electrochemical
gradient because there are more positive sodium ions on the
outside of the cell.
· The pumps also move Potassium out but the membrane is
permeable o potassium so it diffuses back out through
potassium channels.
· This makes the outside of the cell positively charged compared…read more

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