Download Human Physiology - Problem Drill 14: Cardiovascular Physiology

Human Physiology - Problem Drill 14: Cardiovascular Physiology
Question No. 1 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. Which statement does not accurately describe what occurs during an action
potential in cardiac cells?
Question #01
(A) Depolarization is due to influx of sodium ions.
(B) Plateau is due to a decrease in calcium permeability and an increase in
potassium permeability.
(C) Action potential is reached at +20mV.
(D) Repolarization is due to a massive efflux of potassium ions.
(E) Resting potential is -90mV.
A. Incorrect!
Depolarization is due to influx of sodium ions. Resting potential is -90mV and influx
of positively charged ions make the membrane less negative causing
depolarization.
B. Correct!
Plateau is due to a change an increase in calcium permeability and a decrease in
potassium permeability. This leads to less potassium ion leaving while calcium
influxes into the cell.
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Choice
C. Incorrect!
Action potential is reached at +20mV. The massive influx of sodium ions causing
the action potential to peak at +20mV.
D. Incorrect!
Repolarization is due to a massive efflux of potassium ions. The efflux of potassium
ions returns the membrane potential back towards the negative.
E. Incorrect!
Resting potential is -90mV. This is due to sodium channels being closed and not
allowing sodium to enter the cell.
Solution
Myocardial cells have a stable resting potential of -90mV. When depolarization
moves through the cells by gap junctions, the potential becomes more positive.
This is due to the influx of Na+ coming through voltage-gated channels. The
membrane reaches +20mV at the peak of action potential. When the Na+ channels
close, the cells begins to repolarize as K+ leaves the cell through open K+ channels.
The action potential flattens into a plateau due to a decrease in K+ permeability and
an increase in Ca2+ permeability. The Ca2+ channels were activated during
depolarization and they opened slowly. When they finally open, Ca2+ comes rushing
into the cell. At the same time some of the K+ channels closed. This allows the
action potential to sustain for a longer period to time. The Plateau ends when the
Ca2+ channels close and K+ permeability increases. The K+ channels are slow to
open at first but one open there is massive efflux and rapid repolarization. The cell
returns back to resting potential at -90mV.
The correct answer is (B).
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Question No. 2 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Which of the following depict the correct sequence of blood flowing through the
pulmonary circuit?
Question #02
(A) Tissue capillaries → Right atrium → Veins→ Vena cava→ Tricuspid Valve →
Right ventricle→ Pulmonary valve→ Pulmonary trunk.
(B) Tissue capillaries → Venules → Veins→ Vena cava→ Right atrium →Tricuspid
Valve → Right ventricle→ Pulmonary trunk→ Pulmonary Arteries
→Pulmonary valve.
(C) Tissue capillaries → Veins → Vena cava→ Venules→ Right atrium →Tricuspid
Valve → Right ventricle→ Pulmonary valve→ Pulmonary trunk→ Pulmonary
Arteries →Lung capillaries.
(D) Tissue capillaries → Venules → Veins→ Vena cava→ Right atrium →Tricuspid
Valve → Right ventricle→ Pulmonary valve→ Lung capillaries→ Pulmonary
trunk→ Pulmonary Arteries.
(E) Vena cava→ Right atrium →Tricuspid Valve → Right ventricle→ Pulmonary
valve→ Pulmonary trunk→ Pulmonary Arteries →Lung capillaries.
A. Incorrect!
The blood does not flow directly from the tissue capillaries into the right atrium.
Blood leaving from the capillaries always goes into venous system.
B. Incorrect!
The blood flow through the pulmonary valve as it leaves the ventricle.
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Choice
C. Incorrect!
The venules are the smallest veins and they feed from the capillaries.
D. Incorrect!
The pulmonary arteries lead to the lung capillaries.
E. Correct!
This is the right sequence of the blood flowing in the pulmonary circuit.
Solution
This diagram represents the blood flow through the pulmonary circuit. This
transports deoxygenated blood from body tissues through the right side of the
heart and into the lungs. Deoxygenated blood starts in the tissue capillaries and
moves through the venules, the veins and through the vena cava (superior for
blood returning from above the heart and inferior if coming from below the heart)
into the right atrium of the heart. The blood then goes through the tricuspid valve
and into the right ventricle. The blood is then pumped out through the pulmonary
valve into the pulmonary trunk and into the pulmonary arteries. These arteries take
the blood into the lungs. Within the lungs oxygen and carbon dioxide are
exchanged.
The correct answer is (E).
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Question No. 3 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Normal heart sounds are directly caused by which of the following events?
Question #03
(A) Excitation of the SA node.
(B) Friction of the blood against the chamber walls.
(C) Contraction of the ventricle muscles.
(D) Closure of the heart valves.
(E) Contraction of the atria muscle.
A. Incorrect!
Excitation of the SA node helps to set the natural pace of the heart.
B. Incorrect!
It is not possible to hear the blood moving against the actual chamber walls. Blood
is heard only when there is resistance to the flow.
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Choice
C. Incorrect!
The contraction of the ventricles pushes the blood out of the heart but does not
directly contribute to the heart sounds.
D. Correct!
The closure of the AV and semilunar valves are directly responsible for the heart
sounds.
E. Incorrect!
The contraction of the atria pushes the blood into the ventricles but does not
directly contribute to the heart sounds.
As atria contract, depolarization is moving to AV node then it moves to the bundle
of His. Ventricular systole begins as muscle contracts. AV valves close due to
upward force of blood. The vibration following the closure of AV valves create the
first heart sounds, “lub”. After contraction, the ventricles relax and the ventricular
pressure decreases. As pressure decreases, this causes blood to flow backwards
and this flow closes the semilunar valves. That vibration created by the valves
closing produces the second heart sound, “dup”.
Solution
The correct answer is (D).
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Question No. 4 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. What is the cardiac output if the heart rate is 86 beats/min and the stroke
volume is 70ml/beat?
Question #04
(A) 5L/min
(B) 156L/min
(C) 6L/min
(D) 60L/min
(E) Impossible to determine
A. Incorrect!
The heart rate changed to 86 beats/min, instead of 72 beats/min.
B. Incorrect!
The two parameters needed to be multiplied and not added.
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C. Correct!
CO = 86 beats/min x 70mL/beat
CO = 6020mL/min
CO = 6L/min
D. Incorrect!
The answer is 6020mL which is the same as 6L.
E. Incorrect!
It is easy to determine with the formula given.
Cardiac output (CO) = Heart Rate x Stroke Volume
CO = 86 beats/min x 70mL/beat
CO = 6020mL/min
CO = 6L/min
Solution
The correct answer is (C).
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Question No. 5 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. Which of the following is not part of the conduction system of the heart?
Question #05
(A) AV node
(B) Bundle of His
(C) AV valve
(D) SA node
(E) Purkinje fibers
A. Incorrect!
The conduction system is made up of autorhythmic cells and fibers that help to
propagate the signal. The AV node is an autorhythmic cell.
B. Incorrect!
The conduction system is made up of autorhythmic cells and fibers that help to
propagate the signal. The bundle of His is special fibers that help to propagate the
electrical signal.
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Choice
C. Correct!
The AV valve function is to prevent backflow of blood from the ventricles into the
atria.
D. Incorrect!
The conduction system is made up of autorhythmic cells and fibers that help to
propagate the signal. The SA node is an autorhythmic cell.
E. Incorrect!
The conduction system is made up of autorhythmic cells and fibers that help to
propagate the signal. The purkinje fibers are special fibers that help to propagate
the electrical signal.
The electrical signals starts with an action potential being generated in an
autorhythmic cells. These cells are called the SA node and they are found in the
right atrium near the entry of the superior vena cava. This signal is spread rapidly
through intercalated disk to another group of autorhythmic cells at the base of the
right atrium called the atrioventriuclar node (AV node). From the AV node the
signal is passes to the bundle of His or the atrioventricular bundles. These bundles
are found in the septum between the two ventricles and they pass the signal to
Purkinje fibers. These fibers come in direct contact with the contractile cells and
active them to cause contraction.
Solution
The correct answer is (C).
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Question No. 6 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
6. Compared to skeletal muscle, cardiac muscle ___________.
Question #06
(A) Lack striations.
(B) Have gap junctions inside of the intercalated disks.
(C) Is not arranged in sarcomeres.
(D) Cells are larger.
(E) Fibers are multinucleated.
A. Incorrect!
Cardiac is striated just like skeletal muscle due to the banding of actin and myosin.
B. Correct!
Cardiac muscle does have gap junctions inside of the intercalated disks that allow
for direct movement of ions.
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Choice
C. Incorrect!
Fibers are arranged in contractile units called sacromeres.
D. Incorrect!
Cardiac muscle fibers are smaller than skeletal muscles.
E. Incorrect!
Cardiac muscle is uninucleated.
Solution
Cardiac muscle is very similar to skeletal muscles because it is striated and
arranged in sarcomeres. It does differ from skeletal muscles in three major ways:
Muscle fibers are smaller, contain one nucleus and are often branched: the t
tubules are larger and branched inside of the cells; and the SR is much smaller and
cardiac muscle does not rely on as much intracellular Ca2+. This is due to the fact
that cardiac muscle needs more extracellular Ca2+ for contraction. One special
feature of myocardium is that it has intercalated disks that play an important role in
functionality of heart muscle. Intercalated disks are interlocking membranes linked
by cell junctions called desmosomes that connect adjacent cells. These disks allow
the electrical signals to flow rapidly from cell to cell. These disks also have gap
junctions that allow direct movement of ions to help with propagation of the signal.
These gap junctions help to spread depolarization in heart muscle in order to
coordinate simultaneous contractions.
The correct answer is (B).
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Question No. 7 of 10
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needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. Which cells do not maintain a stable resting membrane potential?
Question #07
(A) Pacemaker cells
(B) Contractile myocardial
(C) Skeletal muscle cell
(D) Neurons
(E) All of the above
A. Correct!
Pacemaker cells have a resting potential around -60mV but it is not stable and it is
called the pacemaker potential.
B. Incorrect!
Contractile myocardium has a resting potential that is stable and is at -90mV.
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Choice
C. Incorrect!
Skeletal muscle has a resting potential that is stable and is at -70mV.
D. Incorrect!
Neurons have a resting potential that is stable and is at -70mV.
E. Incorrect!
Autorhythmic cells do not have a stable resting potential. So it cannot be all of the
above.
Action potential differs from contractile cells in pacemaker cells. These cells have
an unstable membrane potential around -60mV. This is called pacemaker potential
because the potential never rests at a set number.
The correct answer is (A).
Solution
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Question No. 8 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. The mitral valve is closed:
Question #08
(A) While the ventricle is in diastole.
(B) When the ventricle is in systole.
(C) While the atrium is contracting.
(D) When the blood is coming into the heart from the veins.
(E) The mitral valve is never closed.
A. Incorrect!
The mitral valve separates the left ventricle from the left atrium. When the
ventricles are relaxed the mitral valve is open to allow for blood to fill into the
ventricles.
B. Correct!
The mitral valve is closed when the blood has completely filled into the ventricles.
The ventricles will then contract and this prevents blood from going back into the
atria.
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Choice
C. Incorrect!
When the atria are contracting, this forces all the blood out of the atria and into the
ventricles. The mitral valve is open to allow for free flowing of the blood.
D. Incorrect!
When the blood is coming into the heart from the veins, the mitral valve aisopen to
allow blood to flow freely into the ventricles.
E. Incorrect!
The mitral valve has to close to prevent blood from flowing back into the left atrium
from the left ventricle.
When the ventricles contract, blood pushes against the valves and forces it to close.
The AV valves are different. AV valve on the right side has three flaps (tricuspid
valve). AV valve on the left side has two flaps (bicuspid valve aka mitral valve).
The correct answer is (B).
Solution
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Question No. 9 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. Norepinephrine acts on heart muscle by:
Question #09
(A) Decreasing heart contractility.
(B) Causing a decrease in heart rate.
(C) Blocking the action of calcium.
(D) Decreasing depolarization.
(E) Increasing depolarization.
A. Incorrect!
Catecholamines leads to an increase in action potential which in turn will increase
the action potentials generated.
B. Incorrect!
Catecholaimine increase the influx of cations into the cells which increase the
depolarization and thus increase the heart rate.
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Choice
C. Incorrect!
The catecholamines activate receptors on autorhythmic cells and lead to increase in
influx of calcium and sodium into the cells.
D. Incorrect!
Catecholamines activate receptors on autorhythmic cells that lead to influx of
cations into the cells thus increasing depolarization.
E. Correct!
Catecholamines will increase the flow of sodium and calcium and this will lead to
increase depolarization and faster heart rate.
Catecholamines increase the flow of Na+ and Ca2+ though both the If and the Ca2+
channels by activating the B1 receptors. The more the influx of ions, the fastest
depolarization and the faster the action potential. This increases the heart rate.
The correct answer is (E).
Solution
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Question No. 10 of 10
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10. Which corresponds to atrial depolarization?
Question #10
(A) P wave
(B) QRS complex
(C) T wave
(D) O wave
(E) All of the above
A. Correct!
The P wave corresponds to the depolarization of the atrium.
B. Incorrect!
The QRS complex corresponds to ventricular depolarization.
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Choice
C. Incorrect!
The T wave corresponds to ventricular repolarization while the cells return back to
resting potential.
D. Incorrect!
There is no O wave as part of the ECG.
E. Incorrect!
Each wave corresponds to a different action within the heart. Therefore, they can’t
all lead to atrial depolarization.
There are three components of an ECG. The first wave is the P wave and it
corresponds to depolarization of the atria. The next set of waves is the QRS
complex and this corresponds to ventricular depolarization. The final wave is the T
wave and it corresponds to ventricular repolarization. Atria repolarization occurs
during the QRS complex.
The correct answer is (A).
Solution
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