PDC Test - The Heart

You can earn 0.25 PDC by passing the exam following this article, which has been approved for publication by NCRA's Council of the Academy of Professional Reporters.

The questions are based on the material in the article but some may require additional research. Send your answer sheet to NCRA's Continuing Education Office, 8224 Old Courthouse Road, Vienna, VA 22182, and enclose a check for $40 (member) or $50 (non-member) to cover the processing fee. 

The Heart

Your heart is a bundle of muscles about the size of your fist. If you clench your fist, open it, then clench it again, you can get a rough idea of the action of the heart. But if you open and close your fist, again and again, your muscles will feel tired after a couple of minutes. Your heart, meanwhile, is contracting and dilating at an average rate of 72 times a minute, and the only rest the heart muscles get is the fraction of a second pause between beats.

The heart consists of several layers of muscles arranged in circles and spirals. When the muscles contract, the spirals and circles tighten and the blood is literally squeezed out of the chambers. The contraction that squeezes the blood from the heart is called systole, and the relaxation of the heart muscles is called diastole.

A number of large arteries and veins run into the top of the heart, carrying blood to and from other parts of the body. The walls on one side of the heart are thicker than on the other, and the surface is covered with a number of small arteries and veins. The arteries on the surface of the heart are called the coronary arteries. They carry the blood which, in turn, carries the oxygen, food, and other necessary materials to the muscle fibers of the heart. Of the more than 4,000 gallons of blood pumped through the heart each day, none is absorbed through the chamber walls.

If we could see the inside of the heart we would find four chambers -- two at the top called atria and two at the bottom called ventricles. Each atrium is separated from the ventricle below by a valve. The atrium and ventricle on the right are separated from their counterparts on the left by a wall of muscle called a septum.

By tracing the paths of the blood through the heart, we see that this organ actually is a double pump. Blood flows from the right atrium into the right ventricle (the first pump), which squirts the blood into the lungs. The left ventricle, or second pump, squeezes the blood into the arteries that extend to all parts of the body. The septum prevents blood on the right side from mixing with blood on the left, and vice versa.

The thick ventricle walls do most of the blood pumping. The atria serve mainly as reservoirs, although they do give the blood a boost into the ventricles. A closer look at the pattern of flow shows that ``used'' blood from all parts of the body reaches the heart through big veins called the superior and interior vena cava. The smaller veins from the head and arms drain into the superior vena cava. The inferior vena cava drains the blood from the lower parts of the body. The venae cavae open directly into the right atrium. The blood which has been used by the heart itself drains into the right atrium through a vessel known as the coronary sinus.

The valve that separates the right atrium from the right ventricle prevents the dark or ``used'' from being pushed back into the atrium when the ventricle contracts. This valve is the tricuspid, so called because it has three cusps, or flaps, of tissue. The cusps are controlled tiny papillary muscles. When the papillary muscles contract, they pull on cords attached to the cusps and thus pull open the valves.

With the tricuspid valve closed to prevent backflow, the right ventricle squeezes the dark blood upward and into the pulmonary artery. The pulmonary artery has left and right branches extending into the lungs on either side of the body. As the dark blood flows into the lungs it circulates through capillary beds -- webs of tiny vessels that line the millions of microscopic air sacs. In the air sacs, called alveoli, the blood's red cells exchange carbon dioxide for oxygen. The carbon dioxide is a waste product from the body's tissues. The oxygen helps the tissues perform their various tasks.

The fresh supply of oxygen changes the color of the blood from a dark red to a bright red, and it is ready to be returned to the heart. When the blood returns through the pulmonary veins, it will enter the left atrium. From the left atrium it will be boosted through the mitral, or bicuspid, valve into the left ventricle.

During the next contraction, the fresh blood will be squeezed into the aorta, the great artery from which branches run to all parts of the body. Again, by closing of the valve cusps, the blood is prevented from flowing back into the left atrium.

Since the left ventricle must squeeze the blood throughout the body, its muscle is thicker than that of the right ventricle, which must only squeeze the blood into the air sacs of the lungs. That is why the left ventricle wall is thicker. The space in the ventricles is the same, however. This is because both ventricles contract at the same time, and the volume of blood squeezed into the lungs must be the same as the amount returned.

We should note that arteries always carry blood away from the heart, and veins return blood to the heart. The blood squeezed from the right ventricle to the lungs is dark ``used'' blood from the veins, but the path it follows is still an artery.

Similarly, the bright red blood from the lungs flows through veins to the heart. So it is not always correct to think of an artery as a vessel carrying bright red blood or of a vein as a vessel carrying ``used'' blood. And although some veins appear bluish in color, there's no ``blue'' blood.

When a doctor listens to your heart with a stethoscope, he hears a series of noises through the chest wall. They sound like lubb-DUP. The second, or DUP, sound is shorter and higherpitched than the lubb sound. The lubb is caused by the ``slamming'' shut of the valves between the atria and the ventricles and, at almost the same instant, the contraction of the ventricles. The DUP sound is made by the closing of the semilunar valves in the aorta and pulmonary arteries.

There is a pause between the DUP sound and the next lubb sound. During this fraction of a second, the heart rests. It occurs between the time the ventricles have become partly filled with blood and the start of the next wave of contraction of the atria.

The approximately 72 beats per minute rhythm of the heart begins in a knot of tissue in the atria known as the sinoatrial, or S-A, node. The node contains nerve cells and fibers and muscle cells. It is called the ``pacemaker'' because it generates the ``spark'' or impulse that starts the wave of muscle contraction in the heart. The wave spreads over the muscles of the atria and apparently triggers an impulse in a similar node near the junction of the atria and ventricles. The second, atrioventricular, or A-V, node has branches that run to each of the ventricles and into the papillary muscles of the valves.

Sometimes the rhythm of the heart muscle breaks down, and the fibers contract at random. The lack of coordination of muscle contractions is called fibrillation.

Although the vagus and accelerator nerves send fibers into the heart muscle, they control only the rate of the heartbeat. The heartbeat itself is generated within the S-A and A-V nodes.

The pulse is caused by the blood pressure impact on the arteries as the heart beats and can be felt by placing a finger on the radial artery, at the wrist. Doctors can tell much about the strength and regularity of the blood flow by feeling the pulse of a patient.

After vigorous exercise, your pulse may speed up from around 72 beats per minute to more than 120. But it should return to the original 72 within three minutes.

Blood pressure also permits doctors to study the health of the heart and circulatory system without actually viewing the organs. Each contraction of the ventricles (systole) causes the blood to spurt through the arteries and increases the pressure of blood flow. During the relaxation part of the rhythm (diastole), the pressure decreases.

To measure the systolic and diastolic pressures, an airtight rubber cuff is wrapped around the arm over the brachial artery. The cuff is connected to a glass tube filled with mercury.

Air is pumped into the cuff until it becomes just tight enough to stop the flow of blood in the artery. As the doctor gradually lets the air out of the cuff, just enough blood will squirt through the artery to make a sound that can be heard by placing a stethoscope on the arm. The reading on the tube of mercury at which the first squirt sound is heard will be recorded as the systolic pressure. It will follow the peak of contraction of the heart.

As the doctor continues to reduce the air in the rubber cuff, the sounds heard through the stethoscope will become louder and louder, as more blood squirts through. Finally, the pressure of the rubber cuff will be nearly deflated, the artery will no longer be squeezed, and blood flow will be normal. The sounds will cease. The point where the sounds are loudest, just before they stop, is read as the diastolic pressure.

If the systolic pressure is 120 and the diastolic 80, it will be written as 120/80.

From the heart, blood surges through the aorta to the arteries through the body. From the arteries, smaller vessels called arterioles branch out. From the arterioles, the blood flows to the smallest vessels, the capillaries. The capillaries carry the blood to the individual cells of the body where oxygen and other chemicals are delivered and waste products are collected. The capillaries then connect with venules, which run into veins which, in turn, flow into the venae cavae.

This article and accompanying test were prepared by BAPR member Nancy Patterson of Los Angeles, California. The article ``The Heart'' is reprinted by permission of the American Medical Association from The Human Machine, copyright 1979.

Test for "The Heart - CEU Exam"

1. An average pulse rate of 110 would be considered to be

A. tachycardia
B. bradycardia
C. cardiac arrest
D. cardiac modulation

2. The atria of the heart are also called the

A. ischia
B. subclavians
C. auricles
D. pericardium

3. On the way to the left atria from the right ventricle, blood passes through the

A. tricuspid valve
B. coronary artery
C. right atrium
D. pulmonary veins

4. Pulmonary alveoli are NOT also called

A. alveoli pulmonum
B. matrix vesicles
C. Malpighi's vesicles
D. visiculae pulmonales

5. The left atrioventricular orifice is also called the

A. pulmonary valve
B. tricuspid valve
C. bicuspid valve
D. coronary valve

6. Arrhythmia is a

A. fast rhythm
B. fibrillation
C. slow rhythm
D. palpatation

7. The pacemaker is also known as the

A. coronary artery
B. tricuspid valve
C. right ventricle
D. sinoatrial node

8. Ventricles are

A. smaller than atria because all blood in the atria has already been oxygenated
B. larger than atria because the walls are thinner and they dilate more
C. smaller than atria because they don't pump blood as far
D. larger than atria because they must pump blood farther

9. The blood flows from the venules into

A. capillaries
B. veins
C. arteries
D. arterioles

10. The spark that starts the heart's muscular contraction is generated in the

A. aorta
B. ventricles
C. atrium
D. vena cava

11. Blood in the right ventricle

A. needs to be oxygenated
B. contains a preponderance of oxyhemoglobin
C. is absorbed through the chamber wall
D. just passed through the aorta

12. Blood in the right ventricle

A. is on its way to the lungs
B. has just passed through the mitral valve
C. is on the way from the pulmonary arteries
D. goes next to the coronary artery

13. Systolic pressure is

A. lower than diastolic
B. higher than diastolic
C. taken in the veins
D. taken in the capillaries

14. Most of the blood pumping is done by the walls of the

A. ventricles
B. atria
C. aorta
D. coronaries

15. Blood that has been used by the heart itself returns to the

A. right ventricle
B. left atrium
C. right atrium
D. left ventricle

16. All arteries

A. carry ``used'' blood
B. carry ``red'' blood
C. carry blood from the arterioles
D. carry blood away from the heart

17. The vagus nerve is also called the

A. 10th cranial nerve
B. glossopharyngeal
C. cardiac
D. 12th cranial nerve

18. Blood that has been used to nourish the kidneys flows into the

A. aortic arch
B. superior vena cava
C. coronary sinus
D. inferior vena cava

19. The septum separates

A. veins from arteries
B. atria from ventricles
C. right from left side of the heart
D. superior vena cava from inferior

20. Blood on its way from the lungs to the aorta would pass through the

A. inferior vena cava
B. left ventricle
C. right atrium
D. superior vena cava

21. Relaxation of the heart muscles is called

A. fibrillation
B. systole
C. diastole
D. bradycardia

22. The papillary muscles control

A. the valve cusps
B. the size of the vena cavae
C. lumen of the blood vessels
D. the pacemaker's impulse

23. Carbon dioxide is exchanged for oxygen in the

A. ventricles
B. alveoli
C. pulmonary veins
D. pulmonary artery

24. The myocardium is the

A. heart muscle
B. lining of the heart
C. covering of the heart
D. heart sac

25. On the way from the left atrium to the left ventricle, blood passes through the

A. bicuspid valve
B. coronary valve
C. tricuspid valve
D. aortic valve