Interesting Facts

At rest, the heart pumps 30xs its own weight
each minute.

There are 60,000 miles of blood vessels.

In one day, the heart can pump 7000 L.

In one year, the heart pumps about 5 million L.

The average body contains about 5 L of blood
volume.
Functions of the Heart

Generating blood pressure

Routing blood
– Heart separates pulmonary (lungs to left side)
and systemic (O2 & nutrients) circulations

Ensuring one-way blood flow
– Heart valves ensure one-way flow

Regulating blood supply
– Changes in contraction rate and force match
blood delivery to changing metabolic needs
Size, Shape, Location
of the Heart

Size of a closed fist

Shape
– Apex: Blunt rounded
point of cone (pointed
bottom)
– Base: Flat part at
opposite of end of
cone (rounded top)

Located in thoracic
cavity in mediastinum
(b/w the lungs; 2/3
to left of center)
Pericardium

Encloses the heart and holds it in place

Two layers:
– Outer, fibrous pericardium prevents the
heart from overstretching
– The inner, serous pericardium contains
pericardial fluid to prevent friction
Heart Wall

Three layers:
– Epicardium—thin, transparent outer layer
– Myocardium—cardiac muscle tissue; bulk of
the heart
– Endocardium—lines the inside of the
myocardium and covers the valves
Heart Chambers

Two upper chambers:
Atria
– Receiving chambers
– Separated by
interatrial septum

Two lower chambers:
Ventricles
– Pumping chambers
– Separated by
interventricular septum
Thickness of Heart Chambers

Vary according to each chambers functions.

Atria—thin walls because they only pump
blood to ventricles

Right ventricle—pumps blood to lungs;
slightly bigger than atria

Left ventricle—pump blood to entire body
and keep up with the other chambers;
thickest of the four chambers
Concept Check

What are the functions of the heart?
– Blood pressure, routing blood, one-way blood
flow, regulating blood supply

Name and describe the 3 layers of the
heart.
– Epicardium (thin/transparent outer layer),
myocardium (cardiac muscle tisssue; bulk),
endocardium (lines inside of myocardium &
covers valves)

What is the difference between atria and
ventricles?
– Atria receives blood; ventricles pumps blood
Blood Vessel Structure

Arteries
– Elastic, muscular, arterioles

Capillaries
– Blood flows from arterioles to capillaries
– Most of exchange between blood and interstitial
spaces occurs across the walls
– Blood flows from capillaries to venous system

Veins
– Venules, small veins, medium or
large veins
Valves of the Heart

Four valves one for
each chamber
– They keep blood from
flowing back to where
it came from
– They open and close in
response to the
pressure of blood
against them
Valves of the Heart

Atrioventricular
(cuspid) valves
– Tricuspid valve —
between right atrium and
right ventricle; 3 flaps or
cusps
– Chordae tendinae —
tendon-like cords that
prevent the cusps from
being pushed back
– Bicuspid valve —between
left atrium and left
ventricle; two cusps
Path of Blood

Right atrium receives deoxygenated blood
from 3 veins:
– Superior Vena Cava—blood from above the heart
– Inferior Vena Cava—blood from below the heart
– Coronary Sinus—blood from the heart wall
Vessels of the Heart
Right Ventricle

Blood goes from to
the pulmonary trunk

Pulmonary trunk
divides into left and
right pulmonary
arteries

Pulmonary arteries
lead to the lungs
From the Lungs

Oxygenated blood
enters the left atrium
via four pulmonary
veins
From the Left Ventricle

Blood enters the ascending aorta

To the coronary arteries

To the arch of the aorta

To the thoracic aorta

To the abdominal aorta
Valves of the Heart

Semilunar Valves
– Pulmonary semilunar
valve— between right
ventricle and pulmonary
artery
– Aortic semilunar valve—
between left ventricle
and the aorta
Blood Supply of the Heart

Coronary Circulation—blood flow through
the myocardium
– Left and right coronary arteries bring blood
to the tissue
– Coronary sinus take deoxygenated blood
from the tissue
Blood Flow Through Heart
Concept Check

What are the 3 types of blood vessels?
– Arteries, veins, capillaries

Describe the flow of blood through the
heart starting w/ the body.
– Body, (SVC, IVC, CS), R Atrium, Tricuspid
Valve, Chordae Tendinae, R Ventricle, Pulmonary
SLV, Pulmonary Trunck, Pulmonary Arteries,
Lungs, Pulmonary Veins, L Atrium, Bicuspid
Valve, Chordae Tendinae, L Ventricle, Aortic
SLV, Aorta, Body
Disorders 

Ischemia —faulty circulation weakens cells
due to lack of oxygen, but the cells don’t
die

Angina Pectoris —chest pain resulting
from ischemia; also from stress, over
exertion, high blood pressure, or narrow
arteries
Disorders 

Myocardial Infarction (MI) —heart attack
– Infarction is the death of an area due to
interrupted blood supply; usually from a clot
– Tissue beyond the clot will die and become
scar tissue
– Location of the infarction area is key to how
serious it is
Conduction System of the Heart

This is an intrinsic regulating system

It does not need a stimulus from the
nervous system

All cardiac muscle is capable of selfexcitation

Cardiac muscle generates its own action
potential
Sinoatrial (SA) Node

Located in the right atrial wall just below the
superior vena cava

Known as the pacemaker of the heart
– Rate of self-excitation is faster than all other heart
fibers
– Its impulses are spread to all the other areas thus
setting the rhythm of the heart
– Both atria will contract at the same time
– This will then depolarize the AV node (ventricles
contract)
Atrioventricular (AV) Node

Located in the interatrial
septum

Last part of atria to
depolarize

This impulse will
depolarize fibers in the
interventricular septum—
bundle of His

This is the only electrical
connection between the
atria and ventricles
Atrioventricular (AV) Node

The impulse passes toward the apex
through left and right bundle branches
to the ventricles

The actual contraction of the ventricles
is done by the Purkinje fibers
Conducting System of Heart
Electrocardiogram (ECG)

A record of the
electrical changes
that accompany the
heartbeat.
Electrocardiogram
Action potentials
through myocardium
during cardiac cycle
produces electric
currents than can be
measured
 Pattern

– P wave
 Atria depolarization
– QRS complex
 Ventricle depolarization
 Atria repolarization
– T wave:
 Ventricle repolarization
Cardiac Arrhythmias
Tachycardia: Heart rate in excess of
100bpm
 Bradycardia: Heart rate less than 60 bpm
 Sinus arrhythmia: Heart rate varies 5%
during respiratory cycle and up to 30%
during deep respiration
 Premature atrial contractions: Occasional
shortened intervals between one
contraction and succeeding, frequently
occurs in healthy people

Alterations in
Electrocardiogram
Cardiac Cycle
Cardiac Cycle

Heart is two pumps that work together,
right and left half

Repetitive contraction (systole) and
relaxation (diastole) of heart chambers

Blood moves through circulatory system
from areas of higher to lower pressure.
– Contraction of heart produces the pressure
Concept Check

Why does the SA node act as the pacemaker?

How does the heart contract without an impulse
from the brain?
– Impulses are spread to other areas setting the rhythm
of the heart
– Intrinsic regulation / Self-excitation / Cardiac muscle
generates own action potentials

What actually contracts the myocardium of the
ventricles?
– Purkinje fibers

What is an infarct?
– Death of an area due to interrupted blood supply;
usually a clot
Concept Check

What does an EKG measure?
– Electrical changes in the heart that accompany heart
beat

Why is QRS bigger than P?
– QRS = contraction of ventricles
– P = contraction of atria

What is a fibrillation or arrhythmia?
– Fibrillation = heart’s electrical activity has become
disordered; contraction rapid, unsynchronized; flutter
rather than beat; heart pumps little or no blood
Heart Rate

Cardiac Output —amount of blood ejected
from the left ventricle into the aorta per
minute

Stroke volume —amount of blood ejected
from the left ventricle per contraction
Factors Affecting Heart Rate

Autonomic control —baroreceptors—neurons
sensitive to blood pressure changes

Chemicals —too much or too little K+, Na+, or Ca+
either increases or decreases heart rate; oxygen
demands

Temperature —increase temperature, increase
heart rate; lower temperature, decrease heart
rate

Emotions —fear, anxiety, anger all increase heart
rate while depression and grief lower heart rate

Sex and age —faster in females; fastest at birth
but slows as one gets older
More Disorders 

Arteriosclerosis - thickening of the walls of the
arteries and loss of elasticity

Atherosclerosis - Deposition of plaque on walls

Congenital defects—a defect that exists at birth
– Interventricular septal defect—hole in septum
– Valvular stenosis—narrowing of a valve
– Arrthymia—any irregularity in heart rhythm
Effects of Aging on the Heart
Gradual changes in heart function, minor
under resting condition, more significant
during exercise
 Hypertrophy of left ventricle
 Maximum heart rate decreases
 Increased tendency for valves to function
abnormally and arrhythmias to occur
 Increased oxygen consumption required to
pump same amount of blood

Heart Sounds

First heart sound or “lubb”
– Atrioventricular valves and surrounding fluid
vibrations as valves close at beginning of ventricular
systole

Second heart sound or “dupp”
– Results from closure of aortic and pulmonary
semilunar valves at beginning of ventricular diastole,
lasts longer

Third heart sound (occasional)
– Caused by turbulent blood flow into ventricles and
detected near end of first one-third of diastole
Blood Pressure
Measure of force exerted by blood against
the wall
 Blood moves through vessels because of
blood pressure
 Measured by listening for Korotkoff
sounds produced by turbulent flow in
arteries as pressure released from blood
pressure cuff

Pulse Pressure



Difference between
systolic (contraction of
ventricles) and diastolic
(relaxation of
ventricles) pressures
Increases when stroke
volume increases or
vascular compliance
decreases
Pulse pressure can be
used to take a pulse to
determine heart rate
and rhythmicity
Concept Check
What types of things would increase your
heart rate? Decrease?
 What is a congenital disorder? Describe
the problems with interventricular septal
defect.
 What is the difference between systole
and diastole if they both measure on the
arteries?
 What causes the heart sounds?
