Chapter 20 Reading Questions Continued
The Heart

Part 3: The Cardiac Cycle

16. Now it is time to put together all of the features of the heartbeat,
better known as the Cardiac Cycle. In describing the events that occur
in the cardiac cycle let's set up the players in this scene.

You are blood drop X and have just entered the right atrium
Your friend is blood drop Y and has just entered the left atrium

In the paragraphs below circle the correct answers from the choices given.

A. Describe atrial systole.

It is the beginning of the cardiac cycle, you drop X have entered the right atrium from the
( superior vena cava,  marginal artery). Drop Y has entered the left atrium from the
(aorta,  left pulmonary vein). The resting heart is in (systole,   diastole). The atria are
(empty,  full), the AV valves are (open,  shut), and the semilunar valves are (open,  closed).
How much blood is in the ventricles at this time? (70%, 30%) capacity! The SA node fires
and depolarizations spread through both atria, this produces the ( T wave, P wave) on the
ECG. Next, both atria contract ( one at a time,  simultaneously ), producing a small increase
in atrial pressure. This is the period of ( rapid ventricular filling, slow ventricular filling ),
and you drop X and drop Y are pushed into the ventricles. Awesome! You have just passed
the ( bicuspid,  tricuspid ) valve and are now inside the (right,   left) ventricle. The atria
contracted for ( .1,  .5) seconds.

B. Describe ventricular systole.

Here you are floating in the right ventricle, but no for long! The action potential has spread
over the heart's conduction system, from the SA node to the ( AV node,  purkinje fibers )
and then down the bundle of His and into the purkinje fibers. Now the ( atria,   ventricles )
begin to depolarize as seen in the ( QRS complex,  T wave ) on the ECG. As the ventricles
begin to contract, the rapid rise in pressure forces the ( semilunar valves,  AV valves )
to snap shut. This produces the first heat sound ( Lubb,  dupp ). You are trapped inside
the right ventricle, drop Y is trapped inside the left ventricle. But wait! The pressure in the
ventricles is still rising, 60 mmHg, 70 mmHg, 80 mmHg! WOW!
The ( semilunar valves,  AV valves ) fly open because the pressure in the ventricles
exceeds the pressure in the ( vena cavas,  pulmonary arteries and aorta ). You drop X,
as well as drop Y had better have your parachutes for you are forcibly ejected from the heart.
It takes ( .25,  .8) seconds for the ventricles to complete their contraction. About
( 30 mls,  70 mls)  of blood is ejected with you, for drop Y it is ( the same,  twice as much). Now, all pressures drop as the ventricles enter ( diastole,  systole ). The AV valves open by moving ( inferiorly,   superiorly ).  The backflow of blood in the pulmonary arteries and aorta
causes the semilunar valves to ( open,  close ).  This produces the ( Lubb,  dupp ) sound.
You are riding smoothly on your way to the ( lungs,  body tissues ) because the heart is
relaxed.  For ( .1,  .4 ) seconds the entire heart is in ( diastole,   systole ). This is indicated
on the ECG as the ( QRS complex,  T wave ). Then a new action potential at the
SA node starts the cardiac cycle all over again.

17. List three reasons why the heart requires a long refractory period.

1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________

How many times does your heart beat over your lifetime?

You live 70 years.
Your heart rate is 70 beats per minute.
There are 60 minutes in an hour.
There are 24 hours in a day.
There are 365 days in a year. _______________________

18. Define the following:

Stoke Volume _______________________________________________
Cardiac Output ______________________________________________
EDV ______________________________________________________
ESV ______________________________________________________
Frank-Starling Law ___________________________________________

Focus Question
Describe the events that occur in the cardiac cycle.

Part 4: Irregular Heart Rhythms

19. Adaptive Arthur has a disturbance in his conduction system called and arrhythmia.
       A. He may have a serious arrhythmia called and AV block due to a
            disturbance in conduction to the AV node.  The causes of this block are:

1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
4. _____________________________________________________
5. _____________________________________________________

Describe the abnormal ECG in an AV block. ______________________
Name the device that can correct an AV block. ___________________

      B. Adaptive Arthur may have another arrhythmia called atrial fibrillation.
           There is no pumping of blood from the atria. The causes may be:

1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________

Describe the abnormal ECG in atrial fibrillation. __________________
Name the drug that is used to slow the heart rate and increase the strength
of contraction. ___________________________________________

     C. A cardiac emergency is called ventricular __________________________
           If the ventricles contract haphazardly and cannot pump blood then the heart must
           be electrically shocked by __________________________
           Note: an apical pulse is done to assess circulatory failure.

     D. If Arthur's heart rate slows to less than 60 BPM, this arrhythmia is
          called ___________________________________________________

The causes are:
1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
4. _____________________________________________________
How would you describe the ECG defection waves? _______________

      E. Arthur's heart rate rise to over 100 BPM without abnormal deflection waves.
          This is called _________________________________________

The causes are:
1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
4. _____________________________________________________
5. _____________________________________________________

Part 5: Regulation of the Heart Rate

20. Describe the control centers in the medulla oblongata. There are two types of
neurons that send impulses to the SA node. They are part of your autonomic nervous system.

A. List four factors that are related to the cardioacceleratory center.

1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________
4. _____________________________________________________

B. List three factors that are related to the cardioinhibitory center.

1. _____________________________________________________
2. _____________________________________________________
3. _____________________________________________________

21. Indicate how each of the following affects the heart rate.

aortic and carotid bodies ____________________________________
thyroid hormones __________________________________________
fever ___________________________________________________
anxiety __________________________________________________
depression _______________________________________________
acidosis/alkalosis __________________________________________
hyperkalemia _____________________________________________
standing up quickly _________________________________________