BPK 105 - FINAL REVIEW QUESTIONS WITH VERIFIED
ACCURATE ANSWERS
Describe the functions of the heart, including the heart structure responsible for each
function. (4 marks) - Answers - 4 Heart Functions:
- Generating Blood pressure
> Contractions of the heart generate blood pressure
- Routing Blood (pulmonary vs. systemic)
>ensures tissues get adequate oxygenated blood and get rid of CO2
- Ensuring one-way blood flow
> heart valves open and close ensuring no blood back flow
> valves in less powerful veins prevent back flow
- Regulating blood supply
> changes in rate and force of heart contraction match blood flow to the changing
metabolic needs of the tissues during rest, exercise, and changes in body position
Trace the flow of blood through the heart. Specify the various chambers, valves, and
vessels and the function of each. Draw the approximate location of the sinoatrial (SA)
node and Atrioventricular (AV) node. (8 marks)
*Note: The information for this question is contained in several figures throughout
chapter 12. - Answers - 1. Deoxygenated Blood enters R. Atrium from systemic route
via the superior and inferior vena cavas and fo=rom heart via the coronary sinus. Most
blood flows into the R ventricle whiel it relaxes from the previous contraction.
2. R Atrium contracts, and deoxygenated Blood passes through tricuspid valve into R.
Ventricle
3. R. Ventricle contracts and pushes blood against the tricuspid valve forcing it closed.
The papillary muscles attached to the cusps of the AV valve by chordae tendonae
contract to prevent the valve from opening into the atrium. High pressure in the ventricle
forces the pulmonary semilunar valve open, and blood flows into the pulmonary trunk.
4. R. Ventricle relaxes and the pressure decreases, the pressure in the pulmonary trunk
becomes higher causing blood to flow back into the pockets of the pulmonary semilunar
valve, forcing it closed
5. Pulmonary trunk branches to form L and R pulmonary arteries carrying blood to the
lungs.
6. Returning oxygenated blood enters the L atrium 4 pulmonary veins. Blood flows into
the left ventricle as it relaxes from previous contraction.
7. L atrium contracts, forcing blood the flow through the mitral valve to fill L ventricle.
8. As the L ventricle begins to contract, blood is pushed against the bicuspid valve
forcing it closed (papillary muscles again)
9. Presure increases from contraction of L ventricle, forces the aortic semilunar valve
open, and blood flows into aorta & to rest of the body
,1. As the L ventricle relaxes, pressure in aorta becomes greater causing the blood to
flow back against the aortic semilunar valve forcing it closed.
- Sinoatrial node located in the superior wall of the right atrium & initiates the heart
contraction
-Atrioventricular node located in the lower R atrium
Draw the action potential that occurs in cardiac muscle. Label the axis and different
phases. Describe which channels are open and closed during each phase, and how
they contribute to the shape of the action potential. (8 marks) - Answers - The
depolarization phase occurs after the opening of voltage-gated sodium channels. The
opening of these channels increases the permeability of the cell membrane to Na+.
Sodium diffuses into the cell resulting in depolarization. The depolarization stimulates
the voltage-gated calcium channels to open causing calcium to diffuse into the cell. The
peak of the depolarization phase stimulates the opening of a few potassium channels
and the closing of the sodium channels. The calcium channels remain open to
counteract the exit of potassium from the cell.
The opening of these voltage-regulated calcium channels is what causes the plateau
phase. The slow diffusion of calcium into the cell acts to slow the repolarization that the
slow diffusion of K+ begins. This is what distinguishes the plateau phase and results in
cardiac muscle fiber action potentials lasting longer than skeletal ones.
When the plateau phase ends, repolarization begins as calcium channels finally close
and many potassium channels open, releasing more potassium from the cell.
Action potentials also exhibit a refractory period that lasts about as long as the plateau
period. The plateau phase and refractory period allow the muscle to contract and relax
almost completely before another begins.
What are the major differences between the cardiac action potential and the skeletal
muscle action potential? What causes these differences? Why is it important for how the
heart functions? (4 marks) - Answers - DEPOLARIZATION:
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) -
Answers - 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) - Answers
- 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
ACCURATE ANSWERS
Describe the functions of the heart, including the heart structure responsible for each
function. (4 marks) - Answers - 4 Heart Functions:
- Generating Blood pressure
> Contractions of the heart generate blood pressure
- Routing Blood (pulmonary vs. systemic)
>ensures tissues get adequate oxygenated blood and get rid of CO2
- Ensuring one-way blood flow
> heart valves open and close ensuring no blood back flow
> valves in less powerful veins prevent back flow
- Regulating blood supply
> changes in rate and force of heart contraction match blood flow to the changing
metabolic needs of the tissues during rest, exercise, and changes in body position
Trace the flow of blood through the heart. Specify the various chambers, valves, and
vessels and the function of each. Draw the approximate location of the sinoatrial (SA)
node and Atrioventricular (AV) node. (8 marks)
*Note: The information for this question is contained in several figures throughout
chapter 12. - Answers - 1. Deoxygenated Blood enters R. Atrium from systemic route
via the superior and inferior vena cavas and fo=rom heart via the coronary sinus. Most
blood flows into the R ventricle whiel it relaxes from the previous contraction.
2. R Atrium contracts, and deoxygenated Blood passes through tricuspid valve into R.
Ventricle
3. R. Ventricle contracts and pushes blood against the tricuspid valve forcing it closed.
The papillary muscles attached to the cusps of the AV valve by chordae tendonae
contract to prevent the valve from opening into the atrium. High pressure in the ventricle
forces the pulmonary semilunar valve open, and blood flows into the pulmonary trunk.
4. R. Ventricle relaxes and the pressure decreases, the pressure in the pulmonary trunk
becomes higher causing blood to flow back into the pockets of the pulmonary semilunar
valve, forcing it closed
5. Pulmonary trunk branches to form L and R pulmonary arteries carrying blood to the
lungs.
6. Returning oxygenated blood enters the L atrium 4 pulmonary veins. Blood flows into
the left ventricle as it relaxes from previous contraction.
7. L atrium contracts, forcing blood the flow through the mitral valve to fill L ventricle.
8. As the L ventricle begins to contract, blood is pushed against the bicuspid valve
forcing it closed (papillary muscles again)
9. Presure increases from contraction of L ventricle, forces the aortic semilunar valve
open, and blood flows into aorta & to rest of the body
,1. As the L ventricle relaxes, pressure in aorta becomes greater causing the blood to
flow back against the aortic semilunar valve forcing it closed.
- Sinoatrial node located in the superior wall of the right atrium & initiates the heart
contraction
-Atrioventricular node located in the lower R atrium
Draw the action potential that occurs in cardiac muscle. Label the axis and different
phases. Describe which channels are open and closed during each phase, and how
they contribute to the shape of the action potential. (8 marks) - Answers - The
depolarization phase occurs after the opening of voltage-gated sodium channels. The
opening of these channels increases the permeability of the cell membrane to Na+.
Sodium diffuses into the cell resulting in depolarization. The depolarization stimulates
the voltage-gated calcium channels to open causing calcium to diffuse into the cell. The
peak of the depolarization phase stimulates the opening of a few potassium channels
and the closing of the sodium channels. The calcium channels remain open to
counteract the exit of potassium from the cell.
The opening of these voltage-regulated calcium channels is what causes the plateau
phase. The slow diffusion of calcium into the cell acts to slow the repolarization that the
slow diffusion of K+ begins. This is what distinguishes the plateau phase and results in
cardiac muscle fiber action potentials lasting longer than skeletal ones.
When the plateau phase ends, repolarization begins as calcium channels finally close
and many potassium channels open, releasing more potassium from the cell.
Action potentials also exhibit a refractory period that lasts about as long as the plateau
period. The plateau phase and refractory period allow the muscle to contract and relax
almost completely before another begins.
What are the major differences between the cardiac action potential and the skeletal
muscle action potential? What causes these differences? Why is it important for how the
heart functions? (4 marks) - Answers - DEPOLARIZATION:
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) -
Answers - 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) - Answers
- 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
