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Human Physiology/The cardiovascular system

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Human Physiology/The cardiovascular system
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Introduction
The heart is the life-giving, ever-beating
muscle in your chest
...

The heart for the average human will
contract about 3 billion times; never
resting, never stopping to take a break
except for a fraction of a second between
beats
...
Many believe that
the heart is the first organ to become
functional
...
The primary function of the
heart is to pump blood through the
arteries, capillaries, and veins
...
Blood
transports oxygen, nutrients, disease
Model of a human heart
causing viruses, bacteria, hormones and
has other important functions as well
...
Americans today have many options to take care of their
heart and circulatory system
...
This chapter is
dedicated to the heart and its many parts
...
It is responsible for pumping blood through the blood
vessels by repeated, rhythmic contractions
...
The term "cardiac" (as in cardiology) means "related to the heart” and comes
from the Greek word kardia, for "heart
...
The cardiac muscle is self-exciting, meaning it has its own conduction system
...
The heart's rhythmic contractions
occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influence such as
exercise or the perception of danger
...
The myocardium is composed of specialized cardiac muscle
cells with an ability not possessed by muscle tissue elsewhere in the body
...
The blood to the myocardium is supplied by the coronary
arteries
...
Failure of the heart to contract properly (for various reasons)
is termed heart failure, generally leading to fluid retention, edema, pulmonary edema, renal insufficiency,
hepatomegaly, a shortened life expectancy and decreased quality of life

Pericardium
The pericardium is the thick, membranous sac that surrounds the heart
...
There are
two layers to the pericardium: the fibrous pericardium and the serous pericardium
...


Epicardium
The layer next to the heart is the visceral layer, also known as the Epicardium
...


Heart Chambers
The heart has four chambers, two atria and two ventricles
...

Atrium
There are two atria on either side of the heart
...
The left atrium contains blood which has been oxygenated and is ready to be sent to the body
...
The left atrium receives
oxygenated blood from the left and right pulmonary veins
...
There are two
ventricles: the right ventricle pumps blood into the pulmonary circulation for the lungs, and the left ventricle pumps
blood into the systemic circulation for the rest of the body
...
Comparing the left and right ventricle, the left ventricle has thicker walls because it
needs to pump blood to the whole body
...


Septum
The interventricular septum (ventricular septum, or during development septum inferius) is the thick wall separating
the lower chambers (the ventricles) of the heart from one another
...
The greater portion of it is thick and muscular and constitutes
the muscular ventricular septum
...


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Human Physiology/The cardiovascular system

Valves
The two atrioventricular (AV) valves are one-way valves that ensure that blood flows from the atria to the ventricles,
and not the other way
...
The sound heard in a heart beat is the heart valves shutting
...
It is located between the right atrium and the right
ventricle
...
When the heart begins to contract, the heart enters a phase called systole, and the atrium
pushes blood into the ventricle
...
When
the ventricular pressure exceeds the pressure in the atrium, the tricuspid valve snaps shut
...
It is also known as the mitral valve due to the resemblance to a
bishop's mitre (liturgical headdress)
...

As it is on the left side of the heart, it must withstand a great deal of strain and pressure; this is why it is made of
only two cusps, as a simpler mechanism entails a reduced risk of malfunction
...
They have flaps that resemble half moons
...
The aortic semilunar valve is located between the ventricle and the aorta
...
Together, the
papillary muscles and the chordae tendinae are known as the subvalvular apparatus
...
The subvalvular apparatus have no
effect on the opening and closing of the valves
...


Complications with the Heart
The most common congenital abnormality of the heart is the bicuspid aortic valve
...
This condition is often undiagnosed until the person develops calcific aortic
stenosis
...
Another common complication of rheumatic fever is thickening and
stenosis (partial blocking) of the mitral valve
...

The aortic valve is a semilunar valve, but it´s called bicuspid because of it´s regular three "cusps" or "semilunar"
valves, and is not to be confused with the left atrioventricular valve, which is more commonly called the mitral
valve, and is one of the two cuspidal valves
...
The heart works
as two pumps, one on the right and one on
the left that works simultaneously
...
Venous
blood
from
systemic
circulation
(deoxygenated) enters the right atrium
through the superior and inferior vena cava
...
The right ventricles contract and
Diagram of the human heart
force the blood through the pulmonary
semilunar valve into the pulmonary trunk
and out the pulmonary artery
...
The new blood is carried in the pulmonary veins that take it to the left atrium
...
The left ventricle contracts forcing blood through the aortic semilunar valve into the ascending aorta
...


Blood Flow After the Heart
Aorta-Arteries-Arterioles-Capillaries-Venules-Veins-Vena Cava

Blood Flow Through Capillaries
From the arterioles, the blood then enters one or more capillaries
...
Inside the capillaries, exchange of oxygen and carbon dioxide takes place
...
The tissue then releases waste, such as carbon dioxide, which then passes through the wall and into the red
blood cells
...
It’s proper functioning is responsible for the delivery
of oxygen and nutrients to all cells, as well as the removal of carbon dioxide, waste products, maintenance of
optimum pH, and the mobility of the elements, proteins and cells, of the immune system
...


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Human Physiology/The cardiovascular system

Arteries
Arteries are muscular blood vessels that carry blood away from the heart, oxygenated and deoxygenated blood
...
Arteries have a thick wall that consists of three layers
...
The artery walls
are thick so that when blood enters under pressure the walls can expand
...
Arterioles have thick smooth muscular walls
...
This
contracting and relaxing affects blood pressure; the higher number of vessels dilated, the lower blood pressure will
be
...


Capillaries
Capillaries are the smallest of a body’s vessels; they connect arteries
and veins, and most closely interact with tissues
...

Because of this, no cell is very far from a capillary, no more than 50
micrometers away
...
This layer is so thin that molecules such as oxygen, water and
lipids can pass through them by diffusion and enter the tissues
...

The "capillary bed" is the network of capillaries present throughout the body
...
This process is called autoregulation and capillary beds usually carry
no more than 25% of the amount of blood it could hold at any time
...


Veins
Veins carry blood to the heart
...
Most of the blood volume is found in the venous system; about 70% at
any given time
...
Veins have low blood pressure
compared to arteries and need the help of skeletal muscles to bring blood back to the heart
...
They also have a thick collagen outer layer,
which helps maintain blood pressure and stop blood pooling
...
The hollow internal cavity in which the
blood flows is called the lumen
...

Veins are used medically as points of access to the blood stream, permitting the withdrawal of blood specimens
(venipuncture) for testing purposes, and enabling the infusion of fluid, electrolytes, nutrition, and medications
(intravenous delivery)
...
Venules have three layers; they have the same makeup
as arteries with less smooth muscle, making them thinner
...
) In contrast, fishes
have a single circulation system
...
Blood in one
circuit has to go through the heart to enter the other circuit
...
In one
day, the blood travels a total of 19,000 km (12,000 miles), or four
times the distance across the U
...
from coast to coast
...
It is carried to the lungs via pulmonary arteries
...
As a result, blood is oxygenated which is then carried to the
Human circulatory system
...
Oxygen rich
red, veins blue
...
This is
important because mitochondria inside the cells should use oxygen to produce energy from the organic compounds
...
Oxygenated blood from the lungs is returned to
the left atrium, then the ventricle contracts and pumps blood into the aorta
...
Cells consume the oxygen and nutrients and add carbon dioxide, wastes, enzymes
and hormones
...


Aorta
The aorta is the largest of the arteries in the systemic circuit
...
The aorta is an elastic artery, and as such is able to distend
...
This stretching gives the potential
energy that will help maintain blood pressure during diastole, as during this time the aorta contracts passively
...
It is formed by the left and right brachiocephalic veins (also referred to as the
innominate veins) which receive blood from the upper limbs and the head and neck
...


Inferior Venae Cavae
The inferior vena cava (or IVC) is a large vein that carries de-oxygenated blood from the lower half of the body into
the heart
...
It
is posterior to the abdominal cavity, and runs along side of the vertebral column on its right side
...
Although blood fills the chambers of the heart, the
muscle tissue of the heart, or myocardium, is so thick that it requires
coronary blood vessels to deliver blood deep into the myocardium
...
The vessels that remove the deoxygenated blood
from the heart muscle are known as cardiac veins
...
These arteries, when healthy, are capable of auto
Heart showing the Coronary Arteries
regulation to maintain coronary blood flow at levels appropriate to the
needs of the heart muscle
...
The coronary
arteries are classified as "end circulation", since they represent the only source of blood supply to the myocardium:
there is very little redundant blood supply, which is why blockage of these vessels can be so critical
...
• Right coronary artery • Left coronary artery Both of these arteries
originate from the beginning (root) of the aorta, immediately above the aortic valve
...
Four percent of people have a third, the posterior coronary artery
...


Hepatic Veins
In human anatomy, the hepatic veins are the blood vessels that drain de-oxygenated blood from the liver and blood
cleaned by the liver (from the stomach, pancreas, small intestine and colon) into the inferior vena cava
...
They can be differentiated into
two groups, the upper group and lower group
...
The lower group rise from the right lobe and caudate lobe, are
variable in number, and are typically smaller than those in the upper group
...


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Human Physiology/The cardiovascular system

Cardiac Cycle
Cardiac cycle is the term used to describe the relaxation and contraction that occur, as a heart works to pump blood
through the body
...
It is considered one of the
four vital signs
...
When resting, the adult human heart beats at about 70 bpm (males) and 75
bpm (females), but this rate varies between people
...
Resting heart rates can be significantly lower
in athletes, and significantly higher in the obese
...
Exercise,
environmental stressors or psychological stress can cause the heart rate to increase above the resting rate
...
In these cases (as happens in some arrhythmias), the heart rate may be considerably higher than
the pulse
...
Throughout the cardiac cycle, the blood pressure increases and decreases
...


Systole
The heart in the systole phase
...
These cells are activated
spontaneously by depolarization of their membranes beyond a
certain threshold for excitation
...
Some calcium ions bind to receptors on the sarcoplasmic
reticulum causing an influx of calcium ions into the sarcoplasm
...
This
allows the myosin heads to bind to the myosin binding sites on the
actin protein filament and contraction results as the myosin heads
draw the actin filaments along, are bound by ATP, causing them to
release the actin, and return to their original position, breaking
The heart in the systole phase
...
The action
potential spreads via the passage of sodium ions through the gap
junctions that connect the sarcoplasm of adjacent myocardial cells
...
Norepinephrine
diffuses across the synaptic cleft binds to the β1-adrenoreceptors – G-protein linked receptors, consisting of seven
transmembrane domains – shifting their equilibrium towards the active state
...
The G-protein is involved in the production of adenosine
3',5'-cyclic monophosphate (cAMP) from adenosine triphosphate (ATP) and this in turn activates the protein kinase
(β-adrenoreceptor kinase)
...
This will of
course, cause more of the calcium receptors in the sarcoplasmic reticulum to be activated, creating a larger flow of

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Human Physiology/The cardiovascular system

9

calcium ions into the sarcoplasm
...
[Phosphodiesterase catalyses the decomposition of cAMP to AMP so that it is no longer able to
activate the protein kinase
...
]
Noradrenaline also affects the atrioventricular node, reducing the delay before continuing conduction of the action
potential via the bundle of HIS
...
Cardiac Diastole is the period of
time when the heart relaxes after contraction in preparation for
refilling with circulating blood
...
Together they are known as complete cardiac diastole
...
When the
pressure in the left ventricle drops to below the pressure in the left
atrium, the mitral valve opens, and the left ventricle fills with
blood that was accumulating in the left atrium
...
When the pressure in the
ventricles rises above the pressure in the atria, these valves close to prevent regurgitation of blood from the ventricles
into the atria
...
As the left ventricle empties, its pressure falls below the pressure in
the aorta, and the aortic valve closes
...
During inspiration, negative intrathoracic pressure causes increased
blood return into the right side of the heart
...
This causes an increased delay in the P2 component of S2
...
The
reduced volume in the right ventricle allows the pulmonic valve to close earlier at the end of ventricular systole,
causing P2 to occur earlier, and "closer" to A2
...
During expiration normally the interval between the two components
shortens and the tone becomes merged
...


Human Physiology/The cardiovascular system

The Heart's Electrical Conduction System
The heart is primarily made up of muscle tissue
...
These can be controlled by the
autonomic nervous system and circulating adrenaline
...
Sometimes when the heart undergoes great damage to one part of the cardiac muscle or the person
incurs an electric shock, the cardiac cycle can become uncoordinated and chaotic
...
This is called fibrillation and can be fatal if not treated within 60 seconds
...

Although all of the heart's cells possess the
ability to generate the electrical impulses (or
action potentials) that trigger cardiac
contraction, the sinoatrial node is what
normally initiates it, simply because it
generates impulses slightly faster than the
other areas with pacemaker potential
...
The SA node emits a new
impulse before either the AV or purkinje
fibers reach threshold
...
These
Schematic representation of the sinoatrial node and the atrioventricular bundle of
His
...
The bundle, represented in red,
cells are modified cardiac myocytes
...
The AV node tapers down into the bundle of HIS, which passes
they do not contract
...
The ultimate distribution cannot be completely shown in this diagram
...

Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the
primary pacemaker
...
These cells form the atrioventricular node (AV node), which is an area between the right atrium and
ventricle, within the atrial septum
...
When there is a pathology in the AV node or purkinje fibers, an ectopic pacemaker can occur in
different parts of the heart
...
The SA node is richly innervated by vagal and sympathetic fibers
...
Stimulation of the vagus nerve causes decrease in the SA node rate
(thereby causing decrease in the heart rate)
...
The sympathetic nerves are distributed to all parts of the heart, especially in
ventricular muscles
...
Parasympathetic stimulation from the vagal nerves decreases the rate of the AV node by causing
the release of acetylcholine at vagal endings which in turn increases the K+ permeability of the cardiac muscle fiber
...
" When this happens, the purkinje fibers in the AV bundle develops a rhythm of their own
...
If not, death of the affected cells will stop the SA node from triggering the heartbeat
AV Node
The atrioventricular node (abbreviated AV node) is the tissue between the atria and the ventricles of the heart, which
conducts the normal electrical impulse from the atria to the ventricles
...
[1] An important property that is
unique to the AV node is decremental conduction
...
The
atrioventricular node delays impulses for 0
...
The reason it is so
important to delay the cardiac impulse is to ensure that the atria are empty completely before the ventricles contract
(Campbell et al, 2002)
...
In certain types of
supraventricular tachycardia, a person could have two AV Nodes; this will cause a loop in electrical current and
uncontrollably-rapid heart beat
...

AV Bundle
The bundle of HIS is a collection of heart muscle cells specialized for electrical conduction that transmits the
electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the
fascicular branches
...
These specialized muscle fibers in the heart were
named after the Swiss cardiologist Wilhelm His, Jr
...
Cardiac muscle is very
specialized, as it is the only type of muscle that has an internal rhythm; i
...
, it is myogenic which means that it can
naturally contract and relax without receiving electrical impulses from nerves
...
The fibers of the Bundle of HIS allow electrical conduction to occur
more easily and quickly than typical cardiac muscle
...
The
bundle of HIS branches into the three bundle branches: the right left anterior and left posterior bundle branches that
run along the intraventricular septum
...
These fibers
distribute the impulse to the ventricular muscle
...
It takes about 0
...
04s for the impulse to travel from the bundle of HIS to the
ventricular muscle
...

Purkinje Fibers
Purkinje fibers (or Purkyne tissue) are located in the inner ventricular walls of the heart, just beneath the
endocardium
...
Purkinje fibers work with the sinoatrial node (SA node) and
the atrioventricular node (AV node) to control the heart rate
...
This causes the muscle tissue of the ventricles to contract and force blood out of the heart — either to
the pulmonary circulation (from the right ventricle) or to the systemic circulation (from the left ventricle)
...

Pacemaker
The contractions of the heart are controlled by electrical impulses, these fire at a rate which controls the beat of the
heart
...
Artificial devices also called pacemakers can be used after damage to the body's intrinsic conduction system to
produce these impulses synthetically
...
This can be detected by an electrocardiogram which measures the
waves of excitation passing through the heart and plotting a graph of potential difference (voltage) against time
...

However if there is fibrillation there will be no apparent pattern
...
This causes the cardiac muscle to stop completely for 5 seconds and when it begins to beat again the
cardiac cycle would have resumed to normal and the heart will be beating in a controlled manner again
...

Circus movement occurs when an impulse begins in one part of the heart muscle and spreads in a circuitous pathway
through the heart then returns to the originally excited muscle and "re-enters" it to stimulate it once more
...
A cause of circus movement is long length pathway in which the muscle is no longer in a refractatory
state when the stimulus returns to it
...
If the Bundle of HIS is blocked, it will result in dissociation between the activity of the atria and that
of the ventricles, otherwise called a third degree heart block
...
A third degree block is very serious medical
condition that will most likely require an artificial pacemaker
...
C
...
Cardiac electrophysiology is
the science of the mechanisms, functions, and performance of the electrical activities of specific regions of the heart
...
The graph can show the heart's rate and rhythm,
it can detect enlargement of the heart, decreased blood flow, or the presence of current or past heart attacks
...
Depending on the results, the patient’s medical history, and a
physical exam; further tests or a combination of medications and lifestyle changes may be ordered
...

QRS
QRS complex- indicates that the ventricles are electrically stimulated (depolarized) to
pump blood out
...

T
T wave- indicates the recovery period (repolarization) of the ventricles
...
Similar to skeletal muscle, the release of Ca+ ions from the
sarcoplasmic reticulum binds to troponin which allows actin to bind with myosin
...
The increase in cytosolic calcium causes calcium ions to bind to receptors on the surface of the
sarcoplasmic reticulum
...
Calcium ions then rush out of the SR and bind to troponin and allow the myosin and
actin to bind together which causes contraction
...

Contraction ends when the level of cytosolic calcium returns to normal resting levels
...
Unless indicated otherwise,
blood pressure refers to systemic arterial blood pressure, i
...
, the pressure in the large arteries delivering blood to
body parts other than the lungs, such as the brachial artery (in the arm)
...
Blood pressure values are universally stated in millimeters of mercury (mmHg)
...
The mean arterial pressure and pulse pressure are other
important quantities
...
These measures of blood pressure are not static, but
undergo natural variations from one heartbeat to another, and throughout the day (in a circadian rhythm); they also
change in response to stress, nutritional factors, drugs, or disease
...
The average high during systole is 120 mmHg
...


Cardiovascular Disease
Cardiovascular disease refers to the class of diseases that involve the heart and/or blood vessels (arteries and veins)
...
These conditions have similar causes, mechanisms, and treatments
...
It is the number 1 cause of death and disability in the United States and
most European countries
...
There is therefore increased emphasis on preventing
atherosclerosis by modifying risk factors, such as healthy eating, exercise and avoidance of smoking
...

Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurysm, and is
a leading cause of chronic renal failure
Atherosclerosis

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Human Physiology/The cardiovascular system

15

Atherosclerosis is a disease affecting the arterial blood
vessel
...
It is caused by the formation of
multiple plaques within the arteries
...
This increases the stiffness, decreases the
elasticity of the artery wall
...
It most commonly becomes
seriously symptomatic when interfering with the coronary
circulation supplying the heart or cerebral circulation
supplying the brain, and is considered the most important
underlying cause of strokes, heart attacks, various heart
diseases including congestive heart failure and most
cardiovascular diseases in general
...

Severe atherosclerosis of the aorta
...


Circulatory Shock
Circulatory Shock is a severe condition that results from reduced blood circulation
...
It is achieved via the
aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system (i
...
clotting
factors)
...

Preventing blood clots reduces the risk of stroke, heart attack and pulmonary embolism
...

Embolism
An embolism occurs when an object (the embolus) migrates from one part of the body (through circulation) and
causes a blockage (occlusion) of a blood vessel in another part of the body
...

Stroke
A stroke, also known as cerebrovascular accident (CVA), is an acute neurological injury whereby the blood supply
to a part of the brain is interrupted
...

~80% of strokes are due to ischemia
...
Ischemic stroke is commonly

Human Physiology/The cardiovascular system
divided into thrombotic stroke, embolic stroke, systemic hypoperfusion (Watershed or Border Zone stroke), or
venous thrombosis
• Hemorrhagic Stroke: A hemorrhagic stroke, or cerebral hemorrhage, is a form of stroke that occurs when a
blood vessel in the brain ruptures or bleeds
...
In addition, blood irritates
brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, it can cause increased
intracranial pressure which physically impinges on brain tissue and restricts blood flow into the brain
...
There
are two types of hemorrhagic stroke: intracerebral hemorrhage, and subarachnoid hemorrhage
...
Many hospitals
have "brain attack" teams within their neurology departments specifically for swift treatment of stroke
...
These clot busters will
dissolve clots before they can cause tissue death and restore normal circulation
...
There are newer, third generation thrombolytics that are safer
...
Often, this blockage
leads to arrhythmias (irregular heartbeat or rhythm) that cause a severe decrease in the pumping function of the heart
and may bring about sudden death
...
It is the leading cause of death for both men and women all over the world
Angina Pectoris
Angina Pectoris is chest pain due to ischemia (a lack of blood and hence oxygen supply) of the heart muscle,
generally due to obstruction or spasm of the coronary arteries (the heart's blood vessels)
...
Veins or arteries from elsewhere in the patient's body are grafted from the aorta to the coronary arteries,
bypassing coronary artery narrowing caused by atherosclerosis and improves the blood supply to the myocardium
(heart muscle)
...
It is not to be confused with "cessation of heartbeat", which is
known as asystole, or with cardiac arrest, which is the cessation of normal cardiac function in the face of heart
disease
...
Congestive heart failure is often undiagnosed due
to a lack of a universally agreed definition and difficulties in diagnosis, particularly when the condition is considered
"mild"
...
Aneurysms most commonly occur in arteries at the base of the
brain (the circle of Willis) and in the aorta (the main artery coming out of the heart) - this is an aortic aneurysm
...
The larger an
aneurysm becomes, the more likely it is to burst
...
A saccular aneurysm resembles a small sack; a fusiform aneurysm is shaped like a spindle
...

Clearing Clogged Arteries
One way to unblock a coronary artery (or other blood vessel) is percutaneous transluminal coronary angioplasty
(PTCA), which was first performed in 1977
...
Over
this wire, a balloon catheter is passed into the segment that is to be opened up
...
When the balloon is hydraulically inflated, it compresses the atheromatous plaque and stretches
the artery wall to expand
...


Dilated and Inflamed Veins
Varicose Veins
Varicose veins are veins on the leg which are large, twisted, and ropelike, and can cause pain, swelling, or itching
...
Varicose veins result due to insufficiency of the valves
in the communicating veins
...
Normally,
blood flows from the superficial to the deep veins, facilitating return of blood to the heart
...
People who have varicose veins are more at risk of
getting a Deep Vein Thrombosis (DVT) and pulmonary embolisms
...
This is usually the most serious if found in a deep vein
...
The disease may also have a genetic
component, as it is known to run in families
...

Slightly less than 1% of all newborn infants have congenital heart
disease
...

Acyanotic Defects
Acyanotic heart defects are those in which there is a normal amount of
oxygen in the bloodstream
...
In VSD blood from the left ventricle is
shunted to the right ventricle, resulting in oxygenated blood returning
into pulmonic circulation
...


Illustration of VSD

Cyanotic Defects
Cyanotic heart defects refer to defects that result in decreased amounts of oxygen in the blood
...
Cyanotic defects include
tetrogy of fallot and transposition of the great arteries
...
This means that the
system needs to deliver oxygen and nutrients to the tissue fluid that surrounds the cells and also take away the
metabolic waste
...
Blood is pumped by the heart into two circuits: the pulmonary and systemic circuits
...
The cardiovascular system works together with all other
systems to maintain homeostasis
...
There are three main ways that they work
together to maintain homeostasis: the lymphatic system receives the excess tissue fluid and returns it to the
bloodstream, lacteals take fat molecules from the intestinal villi and transport them to the bloodstream and both
systems work together to defend the body against disease
...

• 16
...

• Stress, eating high fat foods, obesity, tobacco and alcohol use are just some risk factors of developing heart disease
...

• The length of all your blood vessels lined up is about 60,000 miles long! To put this in perspective, the Earth's
circumference is 40,075
...

• Fitness and Exercise
...

• Lowering LDL cholesterol and high blood pressure
...

• The total length of capillaries in an average adult human is approximately 25,000 mi (42,000 km)
...
The health of the myocardium depends on its blood supply,
and with age there is greater likelihood that arthrosclerosis will narrow the coronary arteries
...
It may enlarge and outgrow its blood supply, thus becoming weaker
...
This process may be slow or rapid
...
Arrhythmias are also more
common with age, as the cells of the conduction pathway become less efficient
...
And the second phase is
about 36 to 48 hours after injury is called the flow phase
...
In the flow phase there is increased levels of catecholamine,
glucocorticoids, and glucagons, normal or elevated insulin levels, catabolic (breakdown), hyperglycemic (high blood
sugar), increased oxygen consumption/respiratory rate, hyperthermia (high body temperature) fever sets in,

19

Human Physiology/The cardiovascular system

20

hypermetabolism, increased insulin resistance, increased cardiac output
...
This in turn
will cause conduction disorder
...
Right is most common and may go untreated
...


Intrinsic Control of heartbeat
• SA node (located in the right atrium near the entrance of the superior vena cava)
• AV node (located at the base of right atrium)
• AV bundle (located in the intraventricular septum between the two ventricles that go in two directions right and left
bundle branches that leave the septum to enter the walls of both ventricle)
• Bundle Branches (the branching off the septum to the walls of the ventricles that run into the purkinje fibers that
then make contact with ventricular myocardial cells to spread the impulse to the rest of the ventricles)

Electrocardiogram
• The P is the atrial depolarization
• QRS is the ventricular depolarization, as well as atrial repolarization
...


Human Physiology/The cardiovascular system

Extrinsic Control of
Heartbeat
Autonomic system with two subdivisions:
the
sympathetic
division
and
the
parasympathetic division
...
By the time I was
15 in 1965, I had two cardiac catherizations at Rhode Island Hospital
...
It wasn't until 1975 that I was told by my family physician
that I should have my heart checked again
...
David Kitzes of Mariam Hospital performed another catherization
...
Kitzes found that I had aortic
stenosis, which is a narrowing of the valve passage by build-up of plaque due to the valve being malformed at birth
...
Kitzes informed me that I could lead a normal life until I was in my fifties or sixties before I would need
corrective surgery
...
My family
physician said that I should see a cardiologist
...
This time I entered the office of Jon Lambrecht, I had never met him before
...
After asking me about my symptoms, which were fatigue, weakness, asthmatic
symptoms, as well as ashen skin color and dizziness, he informed me of how serious my condition was and the only
salvation was immediate open-heart surgery to replace the aortic valve
...

Dr
...
I didn't have a lot of time to think about it
...
The operation was performed by Dr
...
I
...
It has been almost 3 years since the surgery and I am doing better than I could have
expected
...
I am thankful that I lived at a time when medical technology paved the
way for a second chance because of my new aortic heart valve
...


21

Human Physiology/The cardiovascular system
Stroke
Cerebrovascular disease are those that affect blood vessels in the brain and happen to be the third cause of death in
the United States only behind heart disease and cancer
...
Decreased
blood flow also known as ischemia is dangerous to any tissue but brain tissue is even more vulnerable, mainly due to
the high rate of its metabolic reactions
...
For this reason a stroke can kill people within minutes or leave
them with severe brain damage
...
In a occlusive stroke blood flow through a vessel is blocked
...


Summary
As with all of the body systems, the cardiovascular system plays a part in maintaining homeostasis
...
The pumping of the heart
maintains normal blood pressure and proper oxygenation of tissues
...
The vessels are not passive tubes, but rather active contributors
to homeostasis
...


Review Questions
Answers for these questions can be found here [2]
1
...
This carries the most blood at any given time in the body
A) Veins
B) Capillary Beds
C) Veins
D) Aorta
E) Vena Cava
3
...
This is the pacemaker of the heart
A) AV node

22

Human Physiology/The cardiovascular system
B) Purkinje fibers
C) AV Bundle
D) SA node
E) None of these, a pacemaker is surgically inserted
5
...
The T wave in an EKG shows
A) Resting potential
B) Atrial depolarization
C) SA node excitation
D) Ventricle repolarization
E) Purkinje Excitation
7
...
Systolic Pressure is
A) An average of 120 mm Hg
B) Lowers steadily during ventricle systole
C) The highest when blood is being pumped out of the left ventricle into the aorta
D) An average of 80 mm Hg
E) Both A and C
F) Both B and D
9
...
The resulting ischemia or oxygen shortage causes damage and
potential death of heart tissue
...

Arteriole: a small diameter blood vessel that extends and branches out from an artery and leads to capillaries
Atrial natriuretic peptide: Produced in the atria of the heart, it increases urinary excretion of sodium which causes
water loss which in turn the viscosity of the blood is lowered and in turn lowers the blood pressure
...
That is, a stroke involves
the sudden loss of neuronal function due to a disturbance in cerebral perfusion
...
Because of this, a stroke can be
quite heterogeneous
...
Similarly, patients
with the same clinical handicap can in fact have different causes of their stroke
...
It commonly affects the
leg veins, such as the femoral vein or the popliteal vein or the deep veins of the pelvis
...

Fenestrated Capillaries: have openings that allow larger molecules to diffuse
Fibrous Pericardium: a dense connective tissue that protects the heart, anchoring it to the surrounding walls, and
preventing it from overfilling with blood
Heart Rate: term used to describe the frequency of the cardiac cycle
Hepatic Veins: blood vessels that drain de-oxygenated blood from the liver and blood cleaned by the liver (from the
stomach, pancreas, small intestine and colon) into the inferior vena cava
Hypertension or High Blood Pressure: medical condition wherein the blood pressure is chronically elevated

24

Human Physiology/The cardiovascular system
Inferior Vena Cava (or IVC): a large vein that carries de-oxygenated blood from the lower half of the body into the
heart
Intraventricular Septum: the stout wall separating the lower chambers (the ventricles) of the heart from one
another
Left Atrium:receives oxygenated blood from the left and right pulmonary veins
Lub-Dub: first heart tone, or S1; caused by the closure of the atrioventricular valves, mitral and tricuspid, at the
beginning of ventricular contraction, or systole
Lumen: hollow internal cavity in which the blood flows
Lymph: originates as blood plasma that leaks from the capillaries of the circulatory system, becoming interstitial
fluid, filling the space between individual cells of tissue
Mitral valve: also known as the bicuspid valve; prevents blood flowing from the left ventricle into the left atrium
Myocardium: the muscular tissue of the heart
...

Pacemaker Cells: cells that create these rhythmical impulses of the heart
Plaque: an abnormal inflammatory accumulation of macrophage white blood cells within the walls of arteries
Pulmonary Valve: lies between the right ventricle and the pulmonary artery; prevents back-flow of blood into the
ventricle
Pulse: the number of heartbeats per minute
Purkinje Fibers (or Purkinje tissue): located in the inner ventricular walls of the heart, just beneath the
endocardium; specialized myocardial fibers that conduct an electrical stimulus or impulse that enables the heart to
contract in a coordinated fashion
Renin-Angiotension system:
Right Atrium: receives de-oxygenated blood from the superior vena cava and inferior vena cava
Serous Pericardium: functions in lubricating the heart to prevent friction from occurring during heart activity
Semilunar Valves: positioned on the pulmonary artery and the aorta
Sinoatrial Node: (abbreviated SA node or SAN, also called the sinus node): the impulse generating (pacemaker)
tissue located in the right atrium of the heart
Sinusoidal Capillaries: special forms of fenestrated capillaries that have larger opening allowing RBCs and serum
proteins to enter
Systole: contraction of the heart
Systolic Pressure:' the highest point in blood pressure when the blood is being pumped out of the left ventricle into
the aorta during ventricular systole
Superior Vena Cava (SVC): a large but short vein that carries de-oxygenated blood from the upper half of the body
to the heart's right atrium
Thrombus: a blood clot in an intact blood vessel
Tricuspid Valve: on the right side of the heart, between the right atrium and the right ventricle; allows blood to flow
from the right atrium into the right ventricle when the heart is relaxed during diastole
Vasoconstriction: the constriction of blood vessels
Vasodilation: the dilation of blood vessels
Veins:carry de-oxygenated blood from the capillary blood vessels to the right part of the heart
Ventricle: a heart chamber which collects blood from an atrium
Venule: a small blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood
vessels called

25

Human Physiology/The cardiovascular system

References
1
...
Human Anatomy
...
2002
...
www
...
howstuffworks
...
www
...
org
4
...
heartcenteronline
...
Essentials of Anatomy and Physiology, Valerie C
...
howstuffworks
...
htm
[2] http:/ / en
...
org/ wiki/ Human_Physiology/ Appendix_1:_answers_to_review_questions#The_cardiovascular_system

26

Article Sources and Contributors

Article Sources and Contributors
Human Physiology/The cardiovascular system  Source: http://en
...
org/w/index
...
, CommonsDelinker, Danseyffert, Daynaclegg, ElizabethDurham, Fransanfan, Gartoly, Henkeldg, Herbythyme, Hoggle, Islam
...
jpg  Source: http://en
...
org/w/index
...
jpg  License: Public Domain  Contributors: Ekko, 5 anonymous edits
Image:Diagram of the human heart (cropped)
...
wikibooks
...
php?title=File:Diagram_of_the_human_heart_(cropped)
...
jpg  Source: http://en
...
org/w/index
...
jpg  License: Public Domain  Contributors: Arcadian, Fvasconcellos, Origamiemensch, Tooga, 2
anonymous edits
Image:Grafik blutkreislauf
...
wikibooks
...
php?title=File:Grafik_blutkreislauf
...
5  Contributors:
User:Sansculotte
Image:Gray492
...
wikibooks
...
php?title=File:Gray492
...
svg  Source: http://en
...
org/w/index
...
svg  License: GNU Free Documentation License  Contributors: User:Mtcv, User:Reytan
Image:Heart_diasystole
...
wikibooks
...
php?title=File:Heart_diasystole
...
png  Source: http://en
...
org/w/index
...
png  License: Public Domain  Contributors: Foroa, Kauczuk, Moros, 1 anonymous edits
Image:Qrs
...
wikibooks
...
php?title=File:Qrs
...
jpg  Source: http://en
...
org/w/index
...
jpg
 License: Public Domain  Contributors: DO11
...
svg  Source: http://en
...
org/w/index
...
svg  License: Creative Commons Attribution-Sharealike 2
...
gif  Source: http://en
...
org/w/index
...
gif  License: GNU Free Documentation License  Contributors: User:Kalumet
Image:SinusRhythmLabels
...
wikibooks
...
php?title=File:SinusRhythmLabels
...


License
Creative Commons Attribution-Share Alike 3
...
org/ licenses/ by-sa/ 3

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