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The Heart
By: Shirley A. Singree, M.S.
Washington State Community College
Marietta, Ohio
Introduction
• This presentation will cover heart anatomy, blood
circulation, the heart conduction system,
homeostatic imbalances, an electrocardiogram,
cardiac output in relation to heart rate and stroke
volume, and regulation of the heart rate.
• The presentation is produced for an introductory
human anatomy and physiology course, and
should take 1-1.5 hours to complete.
Objectives
• Name and describe the location, size, and
orientation of the heart.
• Name and locate the coverings of the heart,
the heart chambers, heart valves, and major
vessels associated with the heart.
• Describe the pathway of blood through the
heart, to include the pulmonary and systemic
circulation.
• Understand basic homeostatic imbalances of
the heart
Objectives - continued
• Describe the conduction system of the heart.
• Be able to diagram a basic electrocardiogram,
to include overlapping heart sounds and valve
closures.
• Calculate cardiac output, stroke volume, &
heart rate, given CO=HRxSV.
• Describe regulation of heart rate as it is
influenced by the autonomic nervous system.
Resources
• This presentation was completed using
TurningPoint 2008, version 4.0 software.
• The presentation may be viewed as a powerpoint
lecture, or if TurningPoint software is installed &
clicker hardware available, as an interactive
lecture or lecture with a quiz component.
• Additional pictures/diagrams may be added to
supplement this lecture, or chalkboard drawings
will make the presentation more interactive.
Section 1 – Heart Anatomy
• Lies within the mediastinum of the thoracic
cavity just superior to the diaphragm.
• Approximately the size of a large fist, with the
pointed end (apex) pointing to the lower left
side.
• Surrounded and protected by a connective
tissue sac and the ribcage.
• Along with the blood vessels, forms the
cardiovascular system.
Heart Anatomy
• The heart is surrounded by a double layered
connective tissue sac called the pericardium. It
suspends, anchors, and helps protect the heart. It
is the most superficial layer of connective tissue.
• The inner layer of the pericardium is called the
epicardium. It covers the external surface of the
heart.
• Deep to the epicardium lies the myocardium, the
actual heart muscle.
Heart Anatomy
• Deep to the myocardium is the endocardium,
which lines the internal surface of the heart.
• The heart contains four chambers. The
superior two chambers are called atria. The
inferior two chambers are called ventricles.
• There are four valves found within the heart.
• The right atrioventricular valve (tricuspid
valve) is found between the two chambers on
the right side of the heart.
Heart Anatomy
• The left atrioventricular valve (bicuspid, mitral
valve) is found between the two chambers on
the left side of the heart.
• The pulmonary semilunar valve is found
between the right ventricle and the
pulmonary artery.
• The aortic semilunar valve is found between
the left ventricle and the aorta.
Heart Anatomy
• Valves prevent backflow of blood in the heart.
• The atrioventricular (AV) valves function
differently than the semilunar valves due to
structural differences. The AV valves are attached
to chordae tendineae. The chords are anchored
in the ventricle wall via the papillary muscles.
This prevents the valves from swinging backward
up into the atria when closing. The semilunar
valves do not have chord attachments.
Heart Figure
Locate the chambers & valves of the heart. Where are the endocardium,
myocardium, and epicardium located?
Heart Anatomy
• The major vessels associated with the heart
include the aorta, superior vena cava, inferior
vena cava, pulmonary veins, and pulmonary
artery (trunk).
• The superior vena cava drains oxygen-poor blood
into the right atrium from above the diaphragm.
• The inferior vena cava drains oxygen-poor blood
into the right atrium from below the diaphragm.
• The coronary sinus drains oxygen-poor blood into
the right atrium from the myocardium.
Heart Anatomy
• The pulmonary artery (trunk) sends oxygenpoor blood to the lungs via the right and left
pulmonary arteries from the right ventricle.
• The aorta sends oxygen-rich blood to the
systemic circulation from the left ventricle.
• The pulmonary veins bring oxygen-rich blood
to the left atrium from the lungs.
Heart Diagram
Where would the major vessels enter and exit from this heart
diagram?
The most deep connective tissue
covering of the heart is called the
myocardium.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
Is it correct to say that there are six
names for the four valves of the heart?
50%
No
50%
Ye
s
1. Yes
2. No
The pulmonary artery carries oxygenpoor blood to the lungs.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
Is the mitral valve found between the
chambers on the right side of the
heart?
50%
No
50%
Ye
s
1. Yes
2. No
The apex of the heart lies to the upper
left side.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
Section 2 – Blood Flow & Circulation
• The heart tissue (myocardium) gets its oxygen-rich
blood supply from the coronary arteries, which then
drains back to the heart via the coronary veins.
• The right side of the heart carries oxygen-poor blood
that go to the lungs, and the left side of the heart
carries oxygen-rich blood which goes out to the
systemic circulation.
• Gas exchange of oxygen and carbon dioxide occurs in
the lungs. Therefore, the cardiovascular system is
dependent on the respiratory system for its oxygen
supply and removal of carbon dioxide as a waste
product.
Blood Flow & Circulation
Right atrium
Right AV valve
Right
ventricle
Pulmonary semilunar valve
Pulmonary trunk
Right & left pulmonary
arteries
Lungs
Pulmonary veins
Left atrium
Left AV valve
Left ventricle
Aortic semilunar valve
Aorta
Systemic circulation
Blood Flow & Circulation
• Pulmonary circulation of blood accomplishes
two things: 1. addition of oxygen to the
blood 2. removal of carbon dioxide from the
blood
• Systemic circulation of blood accomplishes
two things: 1. removal of oxygen from the
blood 2. addition of carbon dioxide to the
blood
The respiratory system provides
oxygen for the blood via the
pulmonary circulation.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
The right atrium contains oxygen-rich
blood.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
The systemic circulation adds carbon
dioxide to the blood.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
The myocardium gets its blood supply
from the coronary veins.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
Section 3 – Heart Conduction System
• Establishes the fundamental heart rhythm.
• Comprised of five parts.
• 1. Sinoatrial node (SA): sets the basic rhythm (sinus
rhythm) for the heart. Called the pacemaker of the
heart. Contains specialized cells that create their own
action potentials. Located in the right atrium inferior
to the superior vena cava.
• 2. Atrioventricular node (AV): receives action
potentials from the SA node, passes the action
potentials to the Bundle of His. Cells conduct slower to
allow for a delay between the atrial and ventricular
contractions. Located in the interatrial septum.
Heart Conduction System - continued
• 3. Bundle of His (Atrioventricular bundle): Receives action
potentials from the AV node, sends the action potentials to
the left and right bundle branches. Located in the superior
area of the interventricular septum.
• 4. Right & Left Bundle Branches: receives action potentials
from the Bundle of His. Sends action potentials to the
Purkinje fibers.Located medially down the ventricles and
extends around the apex to all Purkinje fibers.
• 5. Purkinje fibers: rapid conduction allows for all
ventricular cells to contract simultaneously. Located
throughout the ventricular walls.
Heart Figure
Cardiac Intrinsic Conduction
System
The __________ is the pacemaker.
33%
no
de
no
de
33%
AS
AV
no
de
33%
SA
1. AV node
2. AS node
3. SA node
The AV node is located in the right
ventricle.
33%
33%
Ye
s
Us
ua
lly
33%
No
1. Usually
2. No
3. Yes
Purkinje fibers are found in the:
Ri
s
33%
tri
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33%
Ve
n
gh
t
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33%
At
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1. Right atrium
2. Atria
3. Ventricles
Action potentials travel through the
Bundle of His located in the:
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3.
I
1. Ventricles
2. Interatrial septum
3. Interventricular
septum
Section 4 – Homeostatic imbalances
• Coronary artery disease – narrowing of the
coronary arteries, can lead to decreased
blood flow (ischemia).
• Arrhythmia – irregular heart rhythm.
• Extrasystole – premature contraction.
• Fibrillation – rapid, irregular rhythm.
• Murmur – abnormal heart sound.
Homeostatic imbalances - continued
• Congestive heart failure – weakened
myocardium, inadequate blood flow due to
decreased pumping ability.
• Tachycardia – fast heart rate, greater than
100 beats/minute.
• Bradycardia – slow heart rate, less than 60
beats/minute.
Murmur: abnormal heart
sound::Fibrillation: __________
1. Rapid, regular
rhythm
2. Irregular rhythm
3. Premature
contraction
4. Rapid, irregular
rhythm
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Section 5 – The Electrocardiogram &
Heart Sounds
• The cardiac cycle, one complete heart beat,
can have the electrical changes recorded with
an EKG (ECG). The basic parts include:
• P wave: Atrial depolarization
• QRS complex: Ventricular depolarization
• T wave: Ventricular repolarization
Heart Sounds
• Heart sounds are created as the heart valves
close.
• The first heart sound is the result of the AV
valves closing. This represents the beginning
of ventricular contraction (systole).
• The second heart sound is the result of the
semilunar valves closing. This represents the
beginning of ventricular relaxation (diastole).
The first heart sound is the result of
the atria contracting.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
The P wave represents atrial systole.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
The T wave represents ventricular
diastole.
se
50%
Fa
l
50%
Tr
ue
1. True
2. False
Section 6 – Cardiac output, Heart rate,
& Stroke Volume
• CO = HR x SV
• Cardiac output represents the amount of blood
pumped out by each ventricle in one minute.
• Stroke volume represents the amount of blood
pumped out by each ventricle per beat.
• Intrinsic heart rate = approximately 100
beats/minute, autonomic nervous system
regulation adjusts this to approximately 70
beats/minute.
Given a heart rate of 65 beats/minute
and a stroke volume of 76 ml/beat,
what is the cardiac output?
25%
m
L/
m
l/ m
in
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in
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25%
1.
16
.8
55
m
l/ m
ut
e
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m
in
25%
in
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4.
94
4940 L/minute
.855 ml/minute
4.94 L/minute
1.16 ml/minute
49
40
1.
2.
3.
4.
Section 7 – Regulation of Heart Rate
• Although the heart has the ability to beat on
its own and set its own pace, it is tied into the
autonomic nervous system. This involuntary
system contains the sympathetic (fight or
flight) and parasympathetic (rest and digest)
systems. Both systems act by releasing their
products on the SA nodal cells to influence the
intrinsic heart rate.
Regulation of Heart Rate - continued
• The sympathetic cardiac nerves release
norepinephrine to increase heart rate during
stressful situations.
• The parasympathetic cardiac nerves release
acetylcholine to decrease heart rate after a
stressful situation.
• Other factors such as hormones, ions, and body
temperature can alter heart rate to a lesser
degree. All act by altering the amount of time
required to reach threshold (-55mV) potential.
The branches of the autonomic
nervous system include:
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1. Somatic and
sympathetic
2. Sympathetic and
parasympathetic
3. Somatic and
parasympathetic
This hormone is released by the
sympathetic nervous system to
increase heart rate.
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pa
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in
1. acetylcholine
2. dopamine
3. norepinephrine
Sympathetic: increase::
parasympathetic:
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cr
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33%
in
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33%
eq
ua
1. equal
2. increase
3. decrease
References
• Marieb, E., Hoehn, K. Anatomy & Physiology. San
Francisco, CA: Pearson Education, Inc. 2008.
• Mohrman, D., Heller, L. Cardiovascular
Physiology. United States of America: The
McGraw-Hill Companies, 2006.
• Heart Figure – Used by permission of Pearson
Education, Inc. (copyrighted material) from
Marieb, E., Hoehn, K. Anatomy & Physiology.
2008.