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The Heart
Cardiac Action Potential
Name ___________________________________
1. How do the waves of depolarization, generated by the autorhythmic cells spread to the
muscle cells? _____________________
2. Depolarizing current from the autorhythmic cells causes the ventricular muscle cells to
______________.
3. Name the three channels essential for generating an action potential and indicate which
way the ions move (circle the correct one):
a. ______________ channels
into or
out of
b. ______________ channels
into or
out of
c. ______________ channels
into or
out of
4. If the sodium channel or the fast calcium channels are open, the inside of the cell would
be relatively more ______________.
5. The pacemaker potential is due to a/an (decreased or increased) efflux of ____ ions
compared to a normal influx of ____ ions.
6. Threshold for the action potential in the SA node is at ____ mV. What channels open,
causing depolarization? ______________
7. The reversal of membrane potential causes the _____ channels to open, causing the
______________ of the membrane.
8. The ______________ pumps sodium out and potassium into the cell, restoring ion
concentrations to their resting levels.
9. Where is calcium stored in the contractile cells? ______________
10. Gap junctions allow what cations to pass into the cardiac contractile cells?
_________________________
11. State the voltage-gated channels responsible for the following stages of the action
potential in cardiac contractile cells:
a. Depolarization ______________________
b. Plateau ___________________________
c. Repolarization ______________________
12. What channels in the autorhythmic cells allow ions to leak in, producing a pacemaker
potential? ______________
13. What channels in the autorhythmic cells bring about depolarization? _____________
1
Conduction System
For questions 1-7 use the following key to match the statements given. Some of the
statements may have more than one answer. Mark all answers that are correct. Key choices
may be used once, more than once, or not at all.
Key:
A.
B.
C.
D.
E.
Sinoatrial (SA) node
Atrioventricular (AV) node
AV bundle (bundle of His)
Bundle branches (right and left)
Purkinje fibers
1. _________ These are made up of specialized cardiac cells that do not contract and are
called nodal cells.
2 _________ These are made up of specialized cardiac cells that do not contract and are
called conducting cells.
3. _________ You would find these in the interventricular septum
4. _________ These are in direct contact with contractile cells of the ventricular myocardium
and are the last fibers of the intrinsic conducting system of the heart.
5. _________ This is the primary pacemaker of a healthy heart.
6. _________ Cells of this structure fire action potentials at a rate of between 70-80 per
minute in the absence of other neuronal or hormonal stimulation.
7. _________ Cells of this structure fire action potentials at a rate of between 40-60 per
minute in the absence of other neuronal or hormonal stimulation.
8. Label the EKG tracing with the
P wave, QRS complex and the
T wave.
9. _____________ What part(s) of the
conducting system of the heart is
active during the P wave?
10. _____________ What part(s) of the
conducting system of the heart is
active during the T wave?
2
Cardiac Cycle
1. Valves open in response to __________________________ on their two sides.
2. List the chambers/vessels that the four valves connect:
Chamber
Valve
Chamber/Vessel
Pulmonary semilunar
Aortic semilunar
Mitral
Tricuspid
3. a. Ventricular filling occurs during ______________ ventricular ____________.
b. Blood flows through the __________, or __________, valves into the ventricles.
4. During ventricular systole, what closes the AV valves?
5. During ventricular systole, what opens the semilunar valves?
6. During isovolumetric relaxation, what closes the semilunar valves?
7. During isovolumetric relaxation, what opens the AV valves?
8. During the four phases listed below, state whether the AV and semilunar valves are open
or closed:
3
Phase
AV Valves
Semilunar Valves
Ventricular filling
Isovolumetric
contraction
Ventricular ejection
Isovolumetric relaxation
Heart Valves Worksheet – Label the valves and vessels of this transverse section of the heart
A. __________________________
A
F
B. __________________________
C. __________________________
D. __________________________
E
E. __________________________
F. __________________________
B
C
D
Applications:
For questions 1 – 3 use the letters in the diagram above as a key for your answers.
1. ______________________________When the ventricles are relaxed (diastole) which of
the valves in the diagram will be open?
2. _____________________________When the ventricles are contracting (systole) which of
the valves in the diagram will be open?
3. _____________________________What valves are closed when the vessels in the
diagram are being filled with blood.
4
4. _____________________________Are the vessels C and E filled with blood during
A) ventricular diastole, B) ventricular systole, or C) in both ventricular diastole and systole?
5. _______________________________________What two structures prevent prolapse of
valves A and F in the diagram.
6. _____________________________a higher pressure in what vessel (as compared to the
heart chamber) causes the closure of Valve B?
7. _____________________________a higher pressure in what vessel (as compared to the
heart chamber) causes the closure of Valve D?
5
Cardiac Output
1. Define cardiac output (CO).
2. Write the equation for CO.
3. Define stroke volume (SV).
4. Write the equation for SV.
5.
Define EDV
6.
Define ESV
7. Write the normal values (include correct units) for the following:
a. HR (heart rate) = ___________________________
b. SV (stroke volume) = ___________________________
c. EDV (end diastolic volume) = ___________________________
d. ESV (end systolic volume) = ___________________________
8.
Given the values for HR and SV, calculate cardiac output:
CO =
If stroke volume is 75 ml/beat and heart rate is 80 beats/min what is the stroke volume?
9. Explain how the following factors affect HR, SV, and CO by placing arrows ( , , or  for
no change) under them.
HR
SV
CO
a.  SNS
____ ____ ____
b.  Venous return
____ ____ ____
c. Exercise
____ ____ ____
d.  Calcium
____ ____ ____
e.  HR
____ ____ ____
10. Why would stroke volume increase with an increase in the sympathetic nervous system
or an increase in calcium?
11. Why would stroke volume increase when heart rate slows down?
Chart 1: Cardiac reflexes. Fill in the chart.
Change in blood
Location
flow that acts
in heart where
upon the heart
reflex
occurs
Cause
Specific trigger
within the heart
Effect
What is the
response of the
heart?
Bainbridge reflex
Frank-Starling law
of the heart
Chart 2: The autonomic nervous system and heart function. Fill in the Chart
Nerve that
directly
stimulates
heart
Neurotransmitter
released at heart
Effect on
heart rate
Effect on
stroke
volume
Effect on
Cardiac
output
Sympathetic
Stimulation
Parasympathetic
Stimulation
Chart 3: Temperature and heart function. Fill in the Chart
Effect on heart rate
Effect on stroke volume
Increase in
Temperature
Decrease in
Temperature
Effect on Cardiac
output
Chart 4: Ion imbalances and heart function. Fill in the chart concerning the effects of homeostatic
ion imbalances.
Condition
Name of Condition
Effect on heart
Excess Ca2+ in ECF
Low Ca2+ in ECF
Excess K+ in ECF
Low K+ in ECF
1. Produce a simplified diagram of heart innervation. In your diagram include how the
medulla oblongata (cardioacceleratory center and cardioinibitory center), higher centers of
the brain, parasympathetic nervous system (via the Vagus and Hypoglossal nerves) and
sympathetic nervous system (via the cardiac nerve and cardiac plexus) interact to influence
the heart rate. Also include what information the nerves carry or what information they
monitor for the medulla. Use your text as reference as a reference.
Heart Practice Problems
1. ____________________________If the pulse is 60 bpm and the stroke volume is 75 ml,
what is the cardiac output?
2. ______________________________An athlete's resting CO is 6,000 ml per minute and
her stroke volume is 100 ml per beat. What is her pulse?
3. _____________________________During exercise, pulse is 120 bpm and stroke volume
is 100 ml. What is the CO?
4. The outermost layer of the pericardial sac is called the fibrous pericardium. It is made
up of _____________________ tissue composed mainly of ________________fibers.
5. _____________________________The serous membrane that lines the pericardial sac is
called?
6. _________________________________________________ The serous membrane that
is on the surface of the heart is called?
7. What is the function of the serous fluid produced by the pericardial membranes?
8. The most important physical characteristic of the endocardium is that it is very
____________ which prevents abnormal _______________ in the chambers of the heart.
9. If the cells of the SA node failed to function, what effect would this failure have on the heart
rate? Why?
10. If the cardioinhibitory center of the medulla oblongata were damaged, which part of the
ANS would be affected and what effect would this damage have on the heart rate?
11. Is the heart always pumping blood when pressure in the left ventricle is rising? Explain.
12. Why is it a potential problem if the heart beats too rapidly?
13. a. What effect would an increased venous return have on the stroke volume?
b._________________________________________Is there a reflex that is associated
with increased venous return and stroke volume? Name it.
14. How would a drug that increases the length of time required for depolarization of
pacemaker cells affect a person's heart rate? Why?
15. What would happen to blood pressure in the pulmonary trunk if the chordae tendineae of
the right ventricle were damaged and became too loose? Why?
16. Given the following pressures: right ventricle 20 mmHg, right atrium 15 mmHg, Aorta 76
mmHg, pulmonary trunk 18 mmHg, left atrium 17 mmHg, and left ventricle 83 mmHg.
Predict which valves of the heart will be open and which will be closed. You might want
to draw a diagram to help you answer this question.
17. _________________________________________________________How would an
increase in ECF concentration of calcium ions affect the strength of a cardiac contraction?
18. What effect would drinking large amounts of a caffeinated beverage like coffee have on
the heart?
19. A heart in tetany could not pump blood. Why?
20. What would happen if the atria and ventricles contracted at the same time?
21. Does blood enter the ventricles during atrial diastole? If yes, what percent of ventricle
filling occurs?
22. Patient A has severely damaged atria that no longer function. Why can Patient A still
survive?
23. How does the structure of the AV valves insure one-way flow of blood in the heart?
24. How does the structure of the SL (semilunar) valves insure a one-way flow of blood in the
heart?
Heart
Identify and Label the items
indicated on
the diagram in
the chart below
17
16
18
(Region)
1
10
2
11
3
12
4
13
5
14
6
15
7
16
8
17
9
18
Heart Section
Label the following structures using the letters indicated below. In addition answer the
question posed for some of the structures.
A. Right Atrium
H. Papillary muscles
B. Left Atrium
I. Interventricular septum
C. Right Ventricle
J. Semilunar valve (Is it aortic or pulmonary?)
D. Left Ventricle
K. Vena Cava (Is it superior or inferior?)
E. Tricuspid Valve
L. Pulmonary vessels (are they pulmonary veins or arteries?)
F. Bicuspid valve
G. Chordae tendineae
Blood Flow Through The Heart
Label the chambers, valves, and vessels on the diagram below.
Color in the blood in the chambers and vessels using red to indicate oxygen rich blood and
blue to represent oxygen poor blood.
Heart: Great Vessels Diagrams – Label the vessels and chambers
Heart Self Test
Label the chambers, vessels, and valves in the diagram below. Using arrows indicate the
blood flow through the heart and vessels. Color in the interventricular septum.
Conduction System of the Heart
1. On the diagram of the heart draw in and label the following structures:
a. Sinoatrial (SA) node
b. Atrioventricular (AV) node
c. AV bundle (bundle of His)
d. Bundle branches (right and left)
e. Purkinje fibers