1
.
Blood
enters
the
right
____________________
carried
by
the
vena
____________________
and
the
left
atrium
carried
by
the
pulmonary
____________________
.
2
.
The
____________________
node
sends
an
electric
signal
that
makes
the
atria
contract
,
but
the
signal
is
held
back
at
the
____________________
node
so
the
ventricles'
contraction
gets
delayed
.
This
allows
blood
to
enter
the
ventricles
.
3
.
After
a
delay
of
approximately
0
.
1
____________________
,
the
signal
is
passed
on
to
the
____________________
of
____________________
,
which
branches
out
to
the
____________________
fibres
and
makes
the
ventricles
contract
.
4
.
The
____________________
valve
prevents
blood
from
flowing
back
to
the
right
atrium
,
and
the
____________________
valve
prevents
blood
from
flowing
back
to
the
left
atrium
.
Blood
is
pumped
from
the
right
ventricle
,
through
the
____________________
valve
onto
the
____________________
and
from
there
to
the
body
;
and
through
the
____________________
valve
onto
the
____________________
artery
and
from
there
to
the
____________________
.
