1) Cardiac Impulses
initiate from the SA
(Sinoatrial) node in
the right atrium
2) Impulses pass
through right and left
atrium walls to the
AV node, causing
both atria to contract,
this is known as
'atrial systole'
3+4) The AV node
conducts impulse
down through bundle
of HIS...
5) ... down through
the left and right
bundle branches to
the apex of the heart
6) Impulses travel up
around ventricle walls
via purkinje fibres,
causing both
ventricles to
contracts; this in know
as 'ventricular systole'
The heart is myogenic -
it generates its own
electrical impulses called
the cardiac cycle
Links between
Conduction System
and The Cardiac Cycle
The heart has a dual pump action with 2
separate pumps that work
simultaneously to pump blood to two
different destinations
The right side of the
heart pumps
de-oxygenated blood
towards the lungs
The left side of the
heart oxygenated
blood towards the
rest of the body
The Cardiac Cycle
Represents the mechanical
events of one hartbeat. One
complete cycle last approx.
0.8 seconds and consists of
2 phases that represent the
contraction and relaxation of
the heart muscle
3) Rising blood pressure forces AV valves
open and blood passively passes into both
ventricles. Semilunar valves close
Systole (0.3s)
4) Both atria and actively forcing
the remaining blood into ventricles
5) Semilunar valves remain closed
6) Both ventricles contract
increasing ventricular pressure
7) Aortic and pulmonary forces
open. AV valve closed
8) Blood forced out into: aorta to
blood tissue/muscles = stroke
volume; pulmonary arteries to lungs.
N.B. only 40% is ejected at rest
during ventricular systole
9) Diastole of the next cardiac
cycles begins. Semilunar valves
close preventing backflow of blood
from aorta and pulmonary arteries
Cardiac Output ,
Stroke Volume
and Heart Rate
Heart Rate (HR)
The number of times the heart
ventricles beat in one minute.
Average resting heart
rate is 70-72 bpm
Max heart rate
is calculate
using 220 - age
Cardiac Output (Q)
The volume of
blood ejected
by heart
ventricles in
one minute
Average =
5litres (Q) =
70ml (SV) x 72
(HR
Stroke
Volume
(SV)
The volume of
blood ejected by
heart ventricles
per beat
Average
Resting Stroke
Volume is 70ml
Changes in
heart rate
Resting
heart rate
1) Average is 72, but a young,
fit aerobic athlete may have
have a resting HR of 60
Anticipatory
Rise
2) Heart rate
increases even
before exercise
due to release
of adrenalin
Rapid increase in HR at start
of exercise due to receptors
3) -Continues use of adrenalin (hormonal,
-Propioreceptors (muscle/joint) relating
to inc. motor activity (neural control),
-Chemoreceptors relating to inc.
CO2/lactic acid (decreased ph) and
decreased O2 levels (neural control)
Continued
but slower
inc. in HR
4) -Continued effect of
Chemoreceptors and
Propiorecptors (neural
control) -Increase in blood
temperature (intrinsic
control) -Increase in Venous
Return (intrinsic control)