The circulatory system consists of three main parts: blood vessels, heart, and blood. The heart pumps blood through arteries and veins using electrical signals from pacemaker cells. Blood carries oxygen, nutrients, waste, and other materials throughout the body via this one-way circulatory route. Key components of the circulatory system include the heart chambers, valves, blood vessels (arteries, veins, capillaries), and the blood flow cycle from lungs to body and back to lungs. The heartbeat and pulse are regulated by the heart's natural pacemaker and electrical conduction system.

1. Blood &
circulation
Colston’s School

2. Circulation
 Your body
resembles a large
roadmap, There
are routes or
“arteries” that take
you downtown to
the “heart” of the
city.

3. 3 Major Parts of the Circulatory
system
• Blood Vessels - routes blood travels
• Heart – pumps or pushes blood through body
• Blood – carries important “ *stuff ” through
body
* Stuff – includes oxygen, food, & waste

4. Blood Vessels : One Way Streets
• Blood Vessels
resemble very
long and skinny
tunnels that are
all through your
body.

5. 3 Types of Blood Vessels
Arteries
Capillaries
Tissue fluid forms here
Arteries get smaller and become arterioles
Veins emerging from capillaries are venules
Veins

6. • The Heart
– 4 chambers ( or compartments )
• 2 upper chambers : Left Atrium
Right
Atrium
• 2 lower chambers : Left Ventricle
Right Ventricle

8. Lub
If you listen to
your heartbeat, it
makes a lub dub
sound.
The lub is when blood
is pushed out of the
heart into the body and
the dub is the reloading
of the heart with more
blood ready to push it
out to the body
Dub

9. Blood Flow through the Human Body
Blood with little oxygen is pumped from the Right Atrium through a valve to
the Right Ventricle and through another valve into the Pulmonary Artery. The
Pulmonary Artery sends it to the Lungs to pick up Oxygen. It’s sent from the
Lungs through Pulmonary Veins to the Left Atrium through a valve to the Left
Ventricle. The Left Ventricle sends it through a valve to the Aorta. The Aorta
is a series of branches that sends oxygenated blood throughout the body.

10. Heart Beat
•
•
•
•
•
•
Effectively the heart is a double pump
It beats from top to bottom
Atria beat first, then the ventricles
This beat is carefully coordinated
A pacemaker sets the beat
Cardiac muscle is special – myogenic and
once kick started beats by itself.

11. Coordinating the Pump: Electrical
Signal Flow

12. Electrical conduction in the Heart
• The Sinoatrial node (SA node), is a group
of autorhythmic cells (main pacemaker of the
heart) in the right atrium near the entry of the
superior vena cava.
• An internodal pathway connects the SA
node to the atrioventricular node (AV
node), a group of autorhythmic cells found
near the floor of the right atrium.
• From the AV node action potentials move into
fiber known as the bundles of his or
atrioventricular bundle. The bundle passes
from the AV node into the wall of the septum
between the ventricles.

13. Electrical conduction in the Heart
• A short way down the septum the bundle
divides into left and right bundle branches.
• These fibers continue downward to the
apex where they divide into many small
purkinje fibers that spread outward
among the contractile cells.

14. The pacemaker - SAN

15. • If the electrical signals from the atria were
conducted directly into the ventricles, the
ventricles would start to contraction at the top.
Then the blood would be squeezed downward
and trapped at the bottom of the ventricle.
• The apex to base contraction squeezes blood
toward the arterial opening at the base of the
heart.
• The AV node also delays the transmission of
action potentials slightly, allowing the atria to
complete their contraction before the ventricles
begin their contraction. This AV node delay is
accomplished by slowing conduction through the
AV node cells.

22. Ventricular Pressure
Note pressure changes in Aorta as
blood enters. The value is always
under ventricles as energy and
pressure is lost via blood friction.
Pressure in Aorta varies as ventricle
pressure increases. As blood leaves
heart and enters Aorta pressure
increases .

23. Electrocardiogram (ECG)
• Composite of all action potentials of nodal
and myocardial cells detected, amplified and
recorded by electrodes on arms, legs and
chest

24. Electrical Activity of the Heart
Einthoven's
triangle
P-Wave – atria
QRS- wave –
ventricles
T-wave –
repolarization

26. • Heart Rate
can be
determined
using a
Stethoscope
400
300
200
200
50 30
100 28
0
376
9
70 40
cam
el
cat
cow
ele
p
gre hant
yw
hal
e
hum
an
lion
mo
use
Heartbeats per
minute
Average Heart Rate of some
Mammals
Mammals

27. Heart Facts
• Hold out your hand and make a fist. If you're a kid, your
heart is about the same size as your fist, and if you're an
adult, it's about the same size as two fists.
• Your heart beats about 100,000 times in one day and
about 35 million times in a year. During an average
lifetime, the human heart will beat more than 2.5 billion
times.
• Give a tennis ball a good, hard squeeze. You're using
about the same amount of force your heart uses to
pump blood out to the body. Even at rest, the muscles of
the heart work hard--twice as hard as the leg muscles of
a person sprinting.