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BIOS225 Thurlby JCCC Final Exam: Questions/Answers
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BIOS225 Thurlby JCCC Final Exam: Questions/Answers
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BIOS225 Thurlby JCCC Final Exam: Questions/Answers7. What prevents electrical signals from passing through the connective tissue
in the heart? Right Ans - Connective tissue is not excitable and is therefore
unable to conduct action potentials.
8. Trace a drop of blood from the superior vena cava to the aorta naming all
structures the drop encounters along its route Right Ans - Superior vena
cava→ right atrium→ tricuspid (right AV) valve→ right ventricle→ pulmonary
(right semilunar) valve→ pulmonary trunk→ pulmonary vein→ left atrium→
mitral (bicuspid, left AV) valve→ left ventricle→ aortic (left semilunar) valve→
aorta
9. What is the function of the AV valves? What happens to blood flow if one of
these valves fails? Right Ans - The AV valves prevent backward flow of
blood. If one fails, blood leaks back into the atrium.
11. If a myocardial contractile cell is placed in interstitial fluid and depolarized
the cell contracts. If Ca2+ is removed from the fluid surrounding the
myocardial cell and the cell is depolarized, it does not contract. If the
experiment is repeated with a skeletal muscle fiber, the skeletal muscle
contracts when depolarized, whether or not Ca2+ is present in the
surrounding fluid. What conclusion can you draw from the results of this
experiment? Right Ans - It is possible to conclude that myocardial cells
require extracellular Ca2+ for contraction but skeletal muscle cells do not.
12. A drug that blocks all Ca2+ channels in the myocardial contractile cell
membrane is placed in the solution around the cell. What happens to the force
of contraction in that cell? Right Ans - If all Ca2+ channels in the muscle cell
membrane are blocked, there will be no contraction. If only some are blocked,
the force of contraction will be smaller than the force created with all
channels open.
13. Which ions moving in what directions cause the depolarization and
repolarization phases of a neuronal action potential? Right Ans - Na+ influx
causes neuronal depolarization, and K+ efflux causes neuronal repolarization.
14. At the molecular level what is happening during the refractory period in
neurons and muscle fibers? Right Ans - what is happening during the
,refractory period in neurons and muscle fibers?, The refractory period
represents the time required for the Na+ channel gates to reset (activation
gate closes, inactivation gate opens).
15. Lidocaine is a molecule that blocks the action of voltage-gated cardiac Na+
channels. What happens to the action potential of a myocardial contractile cell
if lidocaine is applied to the cell? Right Ans - If cardiac Na+ channels are
completely blocked with lidocaine, the cell will not depolarize and therefore
will not contract. Partial blockade will decrease electrical conduction.
16. What does increasing K+ permeability do to the membrane potential of the
cell? Right Ans - Increasing K+ permeability hyperpolarizes the membrane
potential.
17. A new cardiac drug called ivabradine selectively blocks If channels in the
heart. What effect would it have on heart rate and for what medical condition
might it be used? Right Ans - Ivabradine slows heart rate and is used to
lower abnormally high heart rates.
18. Do you think that the Ca2+ channels in autorhythmic cells are the same as
the Ca2+ channels in contractile cells? Defend your answer. Right Ans - The
Ca2+ channels in autorhythmic cells are not the same as those in contractile
cells. Autorhythmic Ca2+ channels open rapidly when the membrane potential
reaches about −50 mV and close when it reaches about +20 mV. The Ca2+
channels in contractile cells are slower and do not open until the membrane
has depolarized fully.
19. What happens to the action potential of a myocardial autorhythmic cell if
tetrodotoxin which blocks voltage-gated Na+ channels, is applied to the cell?
Right Ans - If tetrodotoxin is applied, nothing will happen because there are
no voltage-gated Na+ channels in the cell.
20. In an experiment the vagus nerve, which carries parasympathetic signals
to the heart, was cut. The investigators noticed that heart rate increased. What
can you conclude about the vagal neurons that innervate the heart? Right
Ans - Cutting the vagus nerve increased heart rate, so parasympathetic fibers
in the nerve must slow heart rate.
,21. Name two functions of the AV node. What is the purpose of AV node delay?
Right Ans - The AV node conducts action potentials from atria to ventricles. It
also slows down the speed at which those action potentials are conducted,
allowing atrial contraction to end before ventricular contraction begins.
22. Where is the SA node located? Right Ans - The SA node is in the upper
right atrium.
23. Occasionally an ectopic pacemaker {ektopos Right Ans - out of place}
develops in part of the heart's conducting system. What happens to heart rate
if an ectopic atrial pacemaker depolarizes at a rate of 120 times per minute?,
The fastest pacemaker sets the heart rate, so the heart rate increases to 120
beats/min.
24. During atrial filling Right Ans - is pressure in the atrium higher or lower
than pressure in the venae cavae?, Pressure in the inferior vena cava is higher
than the pressure in the atrium because blood is flowing into the atrium from
the vena cavae.
25. Which chamber—atrium or ventricle—has higher pressure during the
following phases of the cardiac cycle? Right Ans -
32. Using the myocardial cell in Figure 14.10 as a model Right Ans - draw a
contractile cell and diagram how catecholamines increase myocardial
contractility., Your drawing should show a β1- receptor on the cell membrane
activating intracellular cAMP, which should have an arrow drawn to Ca2+
channels on the sarcoplasmic reticulum. Open channels should be shown
increasing cytoplasmic Ca2+. A second arrow should go from cAMP to Ca2+-
ATPase on the SR and the cell membrane, showing increased uptake in the SR
and increased removal of Ca2+ from the cell.
33. A person's aortic valve opening has become constricted Right Ans -
creating a condition known as aortic stenosis. Which ventricle is affected by
this change? What happens to the afterload on this ventricle?, The aortic valve
is found between the left ventricle and the aorta. A stenotic aortic valve would
increase afterload on the ventricle.
3. Put the following structures in the order in which blood passes through
them starting and ending with the left ventricle: Right Ans - a—e—d—b—f
, —c—a left ventricle, aorta, systemic arteries, systemic veins, right ventricle,
pulmonary circulation, left ventricle
4. The primary factor causing blood to flow through the body is a(n) gradient.
In humans Right Ans - the value of this gradient is highest at the and in the .
It is lowest in the . In a system in which fluid is flowing, pressure decreases
over distance because of ., pressure, left ventricle, aorta, right atrium, friction
5. If vasodilation occurs in a blood vessel Right Ans - pressure
(increases/decreases)., decreases
6. The specialized cell junctions between myocardial cells are called . These
areas contain that allow rapid conduction of electrical signals. Right Ans -
intercalated disks, gap junctions
7. Trace an action potential from the SA node through the conducting system
of the heart Right Ans - SA node to internodal pathways to AV node to
bundle of His (left and right branches) to Purkinje fibers to ventricular
myocardium
8. Distinguish between the two members of each of the following pairs: a. end-
systolic volume and end-diastolic volume, b. sympathetic and
parasympathetic control of heart rate, c. diastole and systole, d. systemic and
pulmonary circulation, e. AV node and SA node Right Ans - ESV—volume of
blood in ventricle at end of contraction; EDV—volume of blood in the ventricle
at beginning of contraction, (b) Sympathetic increases heart rate;
parasympathetic decreases heart rate. (c) Diastole = relaxation; systole =
contraction (d) Pulmonary goes to the lungs; systemic goes to rest of body. (e)
SA node is the (atrial) pacemaker; AV node transmits signals from atria to
ventricles.
10. What events cause the two principal heart sounds? Right Ans -
Vibrations from AV closure cause the "lub" sound and from semilunar valve
closure cause the "dup" sound.
12. List the events of the cardiac cycle in sequence Right Ans - beginning
with atrial and ventricular diastole. Note when valves open and close.
Describe what happens to pressure and blood flow in each chamber at each
step of the cycle.
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