BPK 105 - Review
EXAM QUESTIONS AND
VERIFIED CORRECT
ANSWERS GRADED A+
LATEST 100% GUARANTEED
PASS
Depolarization in cardiac muscle differs from skeletal because in a skeletal muscle
depolarization, the only ions involved are Na+ and K+. In cardiac muscled depolarization, the
initial diffusing on Na+ in stimulates volatage-gated Ca2+ channels to open, and Ca2+ diffuses
into the membrane, contributing to the overall depolarization
PLATEAU PHASE:
Skeletal muscle does not even have a plateau phase. In cardaic muscle it happens when the
sodium channels close and some K+ channels open, starting a slow repolarization. However,
because the Ca2+ channels remain open, they function to slow the repolarization even further.
This is what makes the cardiac action potential so much longer than the skeletal muscle action
potential (500ms vs 2ms)
REPOLARIZATION
In skeletal muscle repolarization the Na+ channels close while K+ channels remain open until
repolarization is complete and membrane potential has returned to rest. In cardiac
repolarization is similar, however since the Na+ channels have already closed, instead the Ca2+
channels close and many more K+ channels open allowing the potassium to diffuse out (similar
to skeletal) until resting membrane potential is restored.
,What is the role of the Sinoatrial (SA) node in the heart? Describe the conduction system of the
heart. How does this conduction system facilitate the smooth coordinated contraction of the
heart that is important for it to function as a pump? (4 marks) - CORRECT ANSWER-The
sinoatrial node in the upper wall of the right atrium functions as the heart's pacemaker,
controlling the timing of the muscle contractions using action potentials. It does this by sending
action potentials across the atrial walls causing atrial contraction, and to another area called the
atrioventricular (AV) node. The AV node then transfers the action potentials down the
atrioventricular bundle; specialized cardiac muscle that extends through the fibrous skeleton of
the atrium and down through the interventricular septum of the heart. When the AV bundle
reaches the bottom of the septum it is divided into two left and right bundle branches the carry
the action potentials to the apex of the left and right ventricles. Finally, at the ends of the AV
bundle branches, small bundles form by the conducting tissue called Purkinje fibers, which carry
the action potentials to the muscle of the ventricular walls causing ventricular contraction. The
ventricles rely heavily on the conduction system to be able to produce coordinated contractions.
The conduction system facilitates coordinated contractions in many ways. One way it allows the
heart to function as a pump is that the SA node will not send a new action potential until the
ventricles have completely relaxed from the last one. This coordinated succession of action
potentials ensures that the muscles does not get overworked, and that nothing interferes with
the pumping of blood inside the muscle or outside in the body. A second way the heart
maintains a reliable pumping mechanism is that in the event that the SA node for some reason
becomes unable to function then another area of the heart, like the atrioventricular node, will
become the new pacemaker.
Draw a typical Electrocardiogram (ECG) trace. Label each of the phases and describe the
electrical and contractile events in the heart during each phase. (6 marks) - CORRECT ANSWER-
Consists of a P wave, QRS complex, and T wave.
P wave = depolarization of atrial myocardium, the beginning precedes the onset of atrial
contraction
QRS complex = 3 waves (Q,R,& S), depolarization of the ventricals and beginning precedes
ventricular contraction
T wave = ventricle repolarization and the beginning precedes ventricular relaxation.
In the PQ (or PR interval b/c Q wave is very small) : the atria contract and begin to relax. At the
end of PQ the ventricles depolarize.
, The QT interval extends from beginning of QRS to end of T : represents ventricular
depolarization and repolarization
ECG can't determine contraction force or blood pressure but is good fro diagnosing cardiac
abnormalities
There are waves for atrial repolarization but they are overpowered by the QRS complex.
A trained athlete has a lower resting heart rate than a sedentary person, yet the resting cardiac
output of both is essentially the same. What do you think accounts for this? Define cardiac
output and its components in your answer. (4 marks) - CORRECT ANSWER-The cardiac output is
the volume of blood pumped by either ventricle in the heart each minute and can be calculated
by multiplying the stroke volume (SV= the volume of blood pumped per ventricle each time the
heart contracts) times the heart rate (HR= the number of times the heart contracts each
minute). Exercise increases the size of the heart, enabling an athlete to have a higher stroke
volume and lower heart rate when at rest. Non-athletes on the other hand, are likely to have a
higher heart rate and lower stroke volume. The difference in value between the athlete's low
heart rate, and the non-athlete's high heart rate is made up for in the difference in value
between the athlete's high stroke volume, and the non-athletes low stroke volume. This
essentially means that an athlete's resting cardiac output can be the same as a non-athlete's
resting cardiac output.
Describe the baroreceptor reflex initiated by a sudden drop in blood pressure. Include the
location of receptors and integration centers and how the nervous system responds to this
change. (5 marks) - CORRECT ANSWER-When a sudden drop in blood pressure occurs, it is
detected by the stretch receptors called baroreceptors located in the aorta and carotid arteries.
The low pressure changes the frequency of action potentials sent by the baroreceptors along
nerve fibres to the medulla oblongata of the brain. The action potentials are received and
integrated by the cardioregulatory center in the medulla oblongata which corrects the dip in
blood pressure by increasing sympathetic stimulation of the heart while decreasing
parasympathetic heart stimulation. If the blood pressure has decreased a large amount, then
the adrenal medulla is also stimulated and the secretion of epinephrine and norepinephrine
EXAM QUESTIONS AND
VERIFIED CORRECT
ANSWERS GRADED A+
LATEST 100% GUARANTEED
PASS
Depolarization in cardiac muscle differs from skeletal because in a skeletal muscle
depolarization, the only ions involved are Na+ and K+. In cardiac muscled depolarization, the
initial diffusing on Na+ in stimulates volatage-gated Ca2+ channels to open, and Ca2+ diffuses
into the membrane, contributing to the overall depolarization
PLATEAU PHASE:
Skeletal muscle does not even have a plateau phase. In cardaic muscle it happens when the
sodium channels close and some K+ channels open, starting a slow repolarization. However,
because the Ca2+ channels remain open, they function to slow the repolarization even further.
This is what makes the cardiac action potential so much longer than the skeletal muscle action
potential (500ms vs 2ms)
REPOLARIZATION
In skeletal muscle repolarization the Na+ channels close while K+ channels remain open until
repolarization is complete and membrane potential has returned to rest. In cardiac
repolarization is similar, however since the Na+ channels have already closed, instead the Ca2+
channels close and many more K+ channels open allowing the potassium to diffuse out (similar
to skeletal) until resting membrane potential is restored.
,What is the role of the Sinoatrial (SA) node in the heart? Describe the conduction system of the
heart. How does this conduction system facilitate the smooth coordinated contraction of the
heart that is important for it to function as a pump? (4 marks) - CORRECT ANSWER-The
sinoatrial node in the upper wall of the right atrium functions as the heart's pacemaker,
controlling the timing of the muscle contractions using action potentials. It does this by sending
action potentials across the atrial walls causing atrial contraction, and to another area called the
atrioventricular (AV) node. The AV node then transfers the action potentials down the
atrioventricular bundle; specialized cardiac muscle that extends through the fibrous skeleton of
the atrium and down through the interventricular septum of the heart. When the AV bundle
reaches the bottom of the septum it is divided into two left and right bundle branches the carry
the action potentials to the apex of the left and right ventricles. Finally, at the ends of the AV
bundle branches, small bundles form by the conducting tissue called Purkinje fibers, which carry
the action potentials to the muscle of the ventricular walls causing ventricular contraction. The
ventricles rely heavily on the conduction system to be able to produce coordinated contractions.
The conduction system facilitates coordinated contractions in many ways. One way it allows the
heart to function as a pump is that the SA node will not send a new action potential until the
ventricles have completely relaxed from the last one. This coordinated succession of action
potentials ensures that the muscles does not get overworked, and that nothing interferes with
the pumping of blood inside the muscle or outside in the body. A second way the heart
maintains a reliable pumping mechanism is that in the event that the SA node for some reason
becomes unable to function then another area of the heart, like the atrioventricular node, will
become the new pacemaker.
Draw a typical Electrocardiogram (ECG) trace. Label each of the phases and describe the
electrical and contractile events in the heart during each phase. (6 marks) - CORRECT ANSWER-
Consists of a P wave, QRS complex, and T wave.
P wave = depolarization of atrial myocardium, the beginning precedes the onset of atrial
contraction
QRS complex = 3 waves (Q,R,& S), depolarization of the ventricals and beginning precedes
ventricular contraction
T wave = ventricle repolarization and the beginning precedes ventricular relaxation.
In the PQ (or PR interval b/c Q wave is very small) : the atria contract and begin to relax. At the
end of PQ the ventricles depolarize.
, The QT interval extends from beginning of QRS to end of T : represents ventricular
depolarization and repolarization
ECG can't determine contraction force or blood pressure but is good fro diagnosing cardiac
abnormalities
There are waves for atrial repolarization but they are overpowered by the QRS complex.
A trained athlete has a lower resting heart rate than a sedentary person, yet the resting cardiac
output of both is essentially the same. What do you think accounts for this? Define cardiac
output and its components in your answer. (4 marks) - CORRECT ANSWER-The cardiac output is
the volume of blood pumped by either ventricle in the heart each minute and can be calculated
by multiplying the stroke volume (SV= the volume of blood pumped per ventricle each time the
heart contracts) times the heart rate (HR= the number of times the heart contracts each
minute). Exercise increases the size of the heart, enabling an athlete to have a higher stroke
volume and lower heart rate when at rest. Non-athletes on the other hand, are likely to have a
higher heart rate and lower stroke volume. The difference in value between the athlete's low
heart rate, and the non-athlete's high heart rate is made up for in the difference in value
between the athlete's high stroke volume, and the non-athletes low stroke volume. This
essentially means that an athlete's resting cardiac output can be the same as a non-athlete's
resting cardiac output.
Describe the baroreceptor reflex initiated by a sudden drop in blood pressure. Include the
location of receptors and integration centers and how the nervous system responds to this
change. (5 marks) - CORRECT ANSWER-When a sudden drop in blood pressure occurs, it is
detected by the stretch receptors called baroreceptors located in the aorta and carotid arteries.
The low pressure changes the frequency of action potentials sent by the baroreceptors along
nerve fibres to the medulla oblongata of the brain. The action potentials are received and
integrated by the cardioregulatory center in the medulla oblongata which corrects the dip in
blood pressure by increasing sympathetic stimulation of the heart while decreasing
parasympathetic heart stimulation. If the blood pressure has decreased a large amount, then
the adrenal medulla is also stimulated and the secretion of epinephrine and norepinephrine
