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The Heart
CARDIAC CIRCULATION
Objectives
1. Identify the structures of the heart.
2. Describe the path of blood through the heart.
3. Describe the pulmonary and systemic circuits
THREE CIRCULATORY SYSTEMS
- There are 3 circulatory systems in your body
1) Systemic
- delivers blood between the heart and body cells (we
have covered this… Describe..)
2) Cardiac
- circulation of blood in the heart
3) Pulmonary
- blood goes to the lungs to be oxygenated
- delivers blood between the heart and the lungs
Systemic circulation:
heart
oxygenated blood
artery
arterioles
capillaries (half blue)
gas exchange
venuoles
deoxygenated blood
veins
heart
• The mammalian heart is a double pump,
separated by a wall of muscles called a
septum
This section of the
system including the
right side of the heart,
deals with the
deoxygenated blood.
Lungs
Body cells
This section of the
system including the
left side of the
heart, deals with the
oxygenated blood.
Each side of the heart is divided into two
chambers: an upper atrium and a lower
ventricle (four chambers in total)
The interior of the heart has:
•4 chambers
– two atria (top chambers)
- two ventricles (bottom chambers)
•4 valves – two atrio-ventricular valves
- two semi–lunar valves
•Septum – a wall
• It is used to push blood
through the body and provides
a connection between our
pulmonary and systemic
circulatory systems
• The heart is supplied by blood via the
coronary arteries (come off main aorta)
Refer to your heart diagram as we move
through the lesson….
You should be able to label it by the end!
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The two top chambers are called the right atrium
and the left atrium. Atria are thin-walled and
flexible allowing for easy filling or collecting of
blood
The two bottom chambers are called the right
ventricle and the left ventricle. Ventricles are
thick-walled and strong enough to pump blood out
of the heart. The left ventricle is the most
muscular chamber of the heart.

The two atrio-ventricular valves lie between the
atria and the ventricles. R
◦ Right it is called the tricuspid valve
◦ Left it is called the bicuspid valve.

The two semi-lunar valves lie between the ventricles
and their attached vessels. They are called the right
and left semi-lunar valves.
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A wall that separates the heart into a right side and a
left side. This ensures that blood in each side of the
heart stays in that side of the heart.
Two Pumps
The right pump on the right side of the heart, collects or
fills with deoxygenated blood coming back from the body
by way of veins and then pumps it to the lungs
The left pump on the left side of the heart, collects or
fills with oxygenated blood coming from the lungs and
pumps it into the body by way of arteries
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There are 4 main vessels that are responsible for
bringing blood into the heart and out of the heart
Right Side – the superior and inferior vena cava bring
deoxygenated blood from the body into the right atrium;
two pulmonary arteries carry this deoxygenated blood
away from the heart and into the right and left lung.
Left Side – the pulmonary veins carry oxygenated blood
from the right and left lung towards the left atrium of
the heart; the aorta carries this oxygenated blood away
from the left ventricle of the heart to the body
• http://www.fed.cuhk.edu.hk/~johnson/teac
hing/transport/animations/HyperHeart.swf
• http://www.mayoclinic.com/health/circulato
ry-system/MM00636
• http://www.nhlbi.nih.gov/health/dci/Diseas
es/hhw/hhw_pumping.html
Your Task
1. Label your diagram of the heart. This could
appear on the test.
2. On your second heart, trace the path of blood
as it enters the heart on its way to the lungs
and then back from the lungs to the body.
1. Use colour to represent oxygenated and
deoxygenated blood.
3. Answer questions 1-4 on page 258 of your
text.
OVERALL CARDIAC CIRCULATION
deoxygenated blood is collected
from your upper body
through the superior
vena cava
from your lower
body through the
inferior vena cava
right atrium
(through atrioventricular tricuspid valve)
right ventricle
(through semilunar valve)
right pulmonary artery
left pulmonary artery
Pulmonary Circuit
left lung
right lung
capillaries -> CO2 exchanged for O2 through simple diffusion
pulmonary veins
left atrium
(through atrioventricular bicuspid valve)
left ventricle
(through semilunar valve)
arteries
arterioles
aorta
veins
venules
capillaries (O2 is dropped off, CO2 is picked up)
Plenary
1. Trace the path of blood through the heart.
2. What is the function of A-V and Semi
lunar valves
3. What is different about the pulmonary
arteries and veins
Control of the Heartbeat
Objectives:
1. Describe the sequence of events involved in
the heart contracting.
2. Explain what intrinsic and extrinsic control
is
3. Explain what pulse and blood pressure is and
how it is measured.
Heart Beat
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Each heartbeat is called a cardiac cycle
On average the heart beats 72 b/minute
Each heartbeat lasts 0.85 seconds
Systole refers to the contraction of the heart
Diastole refers to the relaxation of the heart
One heartbeat consists of the following:
Two atria contract
Two ventricles contract
Four chambers relax
Heart Sounds
• These are sounds produced by the heart
caused mainly by the vibrations produced
when the heart valves close and the blood
bounces back against the walls of the
ventricles or blood vessels
‘LUB – DUB’
First Heart Sound
◦ is the beginning of systole
◦ the sound is a longer and lower pitched ‘lub’
◦ it is caused by vibrations occurring when the A-V valves
close due to the pressure of the ventricles filling with blood
from atria
Second Heart Sound
◦ this sound occurs at the end of systole and the beginning of
diastole
◦ the sound produced is a shorter and sharper pitched ‘dub’
◦ Atria are relaxed and fill with blood
◦ it is caused by vibrations occurring when the semi-lunar
valves close preventing blood from re-entering the
ventricles
 Stethoscope is a diagnostic tool used to help determine heart
sounds of systole and diastole (TRY LISTENING to your
partners heart!!)
HEART MURMUR
• Slush sound after the ‘lub’ heart sound
that may be caused by faulty valves, in
particular the A-V valves, allowing blood
to back flow into the atria from the
ventricles.
• Rheumatic fever may be a cause of faulty
valves
• faulty valves can be surgically corrected
INTRINSIC Control of the
Heartbeat
Intrinsic Control– internal (inside) control of the heartbeat
 The intrinsic conduction system of the heart is responsible for
the rhythmical contraction of the heart
 There are four structures that form this system. They are:
i)
SA node
ii)
AV node
iii)
AV bundle
iv)
Purkinje fibres
 Nodal tissue is a unique muscle tissue of the heart
 It has properties of both muscle and nervous tissue
 Nodal tissue is located in two areas of the heart:
i) the upper dorsal (back) wall of the right atrium (SA node)
ii) the base of the right atrium near the septum (AV node)
SA NODE
• Sinoatrial node sets the heart’s tempo or beat
rate
• Also called the pacemaker
• Initiates the heartbeat and automatically sends
out an excitation impulse every 0.85 seconds
causing atria to contract
• NOTE: when the SA node malfunctions the
heart still beats due to AV nodal tissue but the
beat is slower. This is corrected by inserting an
artificial pacemaker.
A-V NODE
• Atrio-ventricular node
• Upon completion of contraction of the atria the
A-V node sends an impulse through the A-V
bundle which then passes the impulse onto
Purkinje fibres found throughout the periphery
of the ventricles causing them to contract.
SA and AV nodes
Sequence of Contraction
1. SA node initiates an impulse causing both atria to
contract
2. Both atria contract forcing blood into each
ventricle
3. AV node sends impulse onto A-V bundle to the
Purkinje fibres triggering the contraction of both
ventricles
4. Both ventricles contract and force blood into both
arteries (on the right side of the heart the pulmonary
arteries receive the blood and on the left side of the
heart the aorta receives the blood)
5. Heart relaxes allowing the atria to fill with blood
SA and AV nodes
EXTRINSIC Control of the
Heartbeat
 There are two factors
involved in outside control of
the heart. They are the medulla oblongata in the
brainstem and hormones
 The autonomic nervous system has 2 divisions, the
sympathetic and parasympathetic
 The sympathetic system, when activated, increases the
heart rate as directed by the medulla oblongata
 The parasympathetic system, when activated,
decreases the heart rate as directed by the medulla
oblongata
 The hormones epinephrine and norepinephrine, released
by the adrenal medulla, will also increase heart rate.
The medulla contains cardiac and
respiratory centers that play a role in
involuntary functions, such as
breathing, heart rate and blood
pressure.
The hormones epinephrine and
norepinephrine, released by the adrenal
medulla, will also increase heart rate.
Epinephrine and norepinephrine also
produce fight or flight responses such as
increasing heart rate and increasing
blood flow to skeleton muscles … to run
away.

ECG is a recording of electrical changes that occur
in myocardium during a cardiac cycle (one
heartbeat)
P wave – occurs just prior to atrial contraction
QRS wave – occurs just prior to ventricular contraction
T wave – occurs when the ventricles are recovering from contraction
 The purpose of an ECG is to detect various types of abnormalities in the beating of
the heart
Your Task
1. Read the handouts on the Circulatory System
and Blood Vessels and answer the questions.
Plenary
1. What does systole and diastole mean?
2. What causes the ‘Lub’ ‘Dub’ sounds your
heart makes?
3. What is the ‘pacemaker’ of your heart and why
is it called this?
4. Describe the sequence of events involved in
the heart contracting.
5. Explain what intrinsic and extrinsic control is
6. What is a heart murmur.
7. What happens during systole and diastole?
Measuring Pulse and Blood
Pressure
Objectives
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is caused by the rhythmical expansion and
recoil of the arterial walls as blood passes
through the artery
it can be felt (palpated) in any artery close to the
body’s surface
the two most common sites to check for a pulse
are the radial artery and the carotid artery
the pulse is used in place of a direct
measurement of heart rate. It is an estimation
of heart rate
Pulse Points
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Is the pressure or force that blood exerts against
the wall of a vessel
The aorta is under the highest pressure of all the
vessels and BP is lowest in the vena cava
Blood pressure is the greatest in arteries, less in
capillaries and negligible in veins
The further away form the heart the vessel is, the
less pressure the vessel is under
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Systolic pressure is the highest arterial pressure
reached during ejection of blood from the heart
(ventricular contraction)
Diastolic pressure is the lowest arterial pressure
measured while the heart ventricles are relaxing
Normal resting BP is 120/80 mmHg at the site of
the brachial artery
BP in venules and veins is negligible
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Venous return of blood is dependent upon
the following three factors:
 Skeletal muscle contraction
 Valves in the veins
 Respiratory movements
Skeletal muscle contraction moving blood in veins
SPHYGMOMANOMETER
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is a blood pressure cuff
is a diagnostic tool for measuring BP
usually used to measure BP at the brachial
artery
HYPERTENSION
 Is a condition that occurs when arterial BP is
significantly above average most of the time
(at least 140/90 mmHg)
 If not treated it can cause cerebral
hemorrhage (stroke) or heart failure
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Blood pressure accounts for the flow of blood in
the arteries and the arterioles
Skeletal muscle contraction, valves in veins and
respiratory movements account for the flow of
blood in the venules and the veins
Blood velocity gradually decreases further away
from the heart as blood pressure decreases
Blood velocity is greatest in arteries, less in
arterioles, very slow in capillaries, increases slightly
in venules and veins
1. Answer Questions
2. P.263 #1,2,3, 5, 6,7
3. H/W Read about Disorders of the Circulatory
System.
4. Make study notes to help you remember at
least …
• 1 disorder that is associated with the heart
• 1 disorder that is associated with the blood
• 1 disorder that is associated with the blood
vessels.
1.
2.
3.
4.
5.
Explain what pulse and blood pressure is and
how it is measured.
What factors affect heart rate and blood pressure?
How can we determine if these factors are having
an effect on heart rate and blood pressure?
When designing an experiment, why is it
important to only change one variable?
How can you ensure that your investigation is a
fair test?