BPK 105 Final UPDATED Actual Exam
Questions and CORRECT Answers
Describe the functions of the heart including heart structure responsible for each function. -
CORRECT ANSWER✔✔- 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 node and
atrioventricular node - CORRECT ANSWER✔✔- 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. - CORRECT ANSWER✔✔- 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 theses differences? Why is it important for how the heart
functions? - CORRECT ANSWER✔✔- 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 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? - 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
elctrical and contractile events in the heart during each phase. - 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 athelete 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. - 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
