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THE NERVOUS SYSTEM (NEURONS (axon (long tail-like structure (extending…
THE NERVOUS SYSTEM
NEURONS
cells
are specialised
transmit messages
called nerve impulses
around the body
have a cell membrane
cytoplasm with a nucleus
and other organelles
have a very unique appearance
cell body
where the nucleus is located
contains most of the neuron's cytoplasm and organelles
form part
grey matter
found in
spinal cord
brain
dentrites
branched projections
of the cell body
connect
to other neurons
and receive information
from them
axon
long tail-like structure
extending
from cell body
information
passes from here
to the next neuron or cell
groups of axons
called nerves
covered
myelin sheath
increases speed
nerve impulses
form white matter
in the
brain
spinal cord
WHAT IS A NERVE IMPULSE
nerve impulse
electrical signal
travels rapidly
through a neuron
from the dentrites
to the axon
it is
body's way of communicating information
in a chain
from the receptors
to the effectors
when a message
needs to be communicated
sodium ions on the outside
of the cell membrane
and the potassium ions
on the inside change places
for a few milliseconds
electrical charge
on the outside of neuron's cell membrane
reversed from positive to negative
this change
in electrical charge
opens channels
allow the messages
to travel along the chain
SYNAPTIC TRANSMISSION
when the nerve impulse
comes to the end of a axon
it reaches a junction called a synapse
the signal passes across
the synapse to the dendrite
in the next cell
through chemical messengers
called neurotransmitters
this process
is known as
synaptic transmission
steps
nerve impulse
impulse travels
from dentrite
to the end of the axon
at the end of the axon
there are many vesicles
containing neurotransmitters
this is
a presynaptic neuron
the impulse releases
neurotransmitters
into the space
between 2 cells
this junction
is called
synapse
neurotransmitters
interact with receptors
on the other side of the synapse
this is
post-synaptic neuron
or cell
the receptors in the post-synaptic
cell react
this is a dentrite
of the next neuron
or a cell
THREE TYPES OF NEURONS
sensory neurons
carry messages
from the receptors
to the central nervous system
motor neurons
carry messages
from the central nervous system
to the effectors
interneurons
make up
central nervous system
connect
sensory and motor neurons