Zusammenfassung der Ressource
The Cardiovascular System
- The Conduction System
- 6 Steps of system
- 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
- Diastole (0.5s)
- 1) Both avia fill with blood.
AV valves closed
- 2) Atria blood pressure rises
above ventricular pressure
- 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)