explain
pain
section
2
page
36
W
hen themessage reaches the end of the
neurone in the spinal cord (inside your back or
neck) it causes chemicals to be poured out into
the gap (synapse) between the end of the
neurone and neighbouring neurones.
Check out the drawing and note the following:
• The synapse (gap between the neurones).
• Many neurones carryingmessages from the
tissues converge on one neurone to the brain
(this is one way inwhich pain can spread –
one neurone carryingmessages from tissues
could come from the foot, another could come
from the knee).
• There is a neurone that comes down from the
brain. This stops action at the synapse and
dangermessagesmay go no further –more on
this important one later.
• How each tissuemessage neurone releases amix of
chemicals into the synapse – symbolised here by
circles, squares, hearts and stars.
• How at the other side of the synapse, the neurone to
the brain has heart, square and round sensors. This
allows it to respond to some chemicals but not others.
• Basically, round chemicals fit in round sensors,
square chemicals in square sensors, etc etc. If they fit,
they open the sensor. This is called the ‘lock and key’
principle. You have just completed second year
university biology.
The alarmmessagemeets the spinal cord
excitatory chemicals
messages from the tissues
sensors
up to the brain
down from
the brain
inhibiting chemicals
(happy hormones)
synapse
