Mastering A&P 2 CH 18 HW
Drag and drop the labels into the appropriate blanks in the sentences. Each term will be used once.
-The semilunar valves open during the ventricular ejection phase of the cardiac cycle, allowing blood to exit the ventricles. -End diastolic volume and the first heart sound are observed during the isovolumetric contraction phase of the cardiac cycle. -The P wave and subsequent atrial contraction are evident during the ventricular filling phase of the cardiac cycle. -The dicrotic notch occurs during the isovolumetric relaxation phase of the cardiac cycle. Correct The cardiac cycle reflects a series of electrical and mechanical events; these changes can be observed on a series of graphs. The electrocardiogram (ECG) tracing reflects atrial and ventricular depolarization and repolarization. The P wave corresponds to atrial depolarization, the QRS complex to ventricular depolarization (and also atrial repolarization), and the T wave reflects ventricular repolarization. Pressure changes in the left ventricle, aorta, and left atria are correlated to changes in volume as blood moves through the four chambers of the heart; there is passive blood flow and the myocardial layer of the heart is responsible for contraction, or systole, and relaxation, or diastole. Two sets of valves—atrioventricular and semilunar—regulate blood flow and keep blood moving in a one-way direction. As these valves open and close, observe the changes in the pressure and volume graphs as well as the heart sounds that are produced.
Match the term in the left column to the blanks near their definition on the right.
1. Stroke volume (SV): the volume of blood per heart beat pumped out by one ventricle 2. Venous return (VR): the volume of blood per minute flowing into one atrium 3. Heart rate (HR): the number of heart beats per minute 4. Cardiac output (CO): the volume of blood per minute pumped out by one ventricle 5. End diastolic volume (EDV): the volume of blood in one ventricle before contraction 6. End systolic volume (ESV): the volume of blood in one ventricle after contraction
Which of the following INCREASES stroke volume?
exercise Correct Exercise increases venous return, which would in turn increase the amount of blood in the presystolic ventricle (preload).
Now that you have reviewed normal blood flow, why does a patient with left-sided heart failure have a low systolic blood pressure? -The left side of the heart contains the ventricles, so it controls blood pressure. -The left side of the heart pumps blood into the body, so when it fails, less blood will be pumped into the arteries. -The left side of the heart does not directly move blood into the body, but when it fails, the right side will also fail, and that will decrease blood pressure out in the body. -The left side of the heart receives blood from the body, so when it fails, blood will build up in the blood vessels.
The left side of the heart pumps blood into the body, so when it fails, less blood will be pumped into the arteries. Correct Since the left ventricle is the one responsible for pumping blood into the arteries, it makes sense that left-sided heart failure would reduce the amount of blood sent into the arteries and therefore the systolic blood pressure. That is not what brought Mr. G to the doctor, though.
Which statement best describes the autonomic nervous system's role in regulating heart rate?
The parasympathetic division normally inhibits the heart, keeping it beating at a slower rate than it would be on its own Correct The inhibitory signals from the vagus nerve inhibit the heart rate, thus keeping the heart rate lower than it would be if the vagus nerve were severed.
Before Baby A was born, she was not sending much blood to her lungs. Instead, the blood passed through the septal defect into the left atrium, which sent it to the left ventricle and to her body. But why didn't the baby die if no blood was going through her lungs? -She sent her blood out into her mother's body and through her mother's lung instead. -She as so small that the small amount of blood that did go through her lungs was enough. -She was getting her oxygen from the placenta, not from breathing -Before the last trimester, babies use anaerobic respiration, so she did not need oxygen
-She was getting her oxygen from the placenta, not from breathing Correct Before birth, Baby A was fine with an atrial septal defect. In fact, she could not have lived without one −− her heart would have worn out from trying to push blood through the collapsed lungs. Instead, she pushed blood through the umbilical artery into the placenta and picked up oxygen that diffused across from her mother's blood.
The P wave on an electrocardiogram represents __________. -ventricular depolarization -atrial depolarization -ventricular repolarization -atrial repolarization
-atrial depolarization Correct The P wave reflects the depolarization of the atria.
Which heart chamber receives blood from the pulmonary veins? -right ventricle -left atrium -right atrium -left ventricle
-left atrium Correct Yes, the left atrium receives oxygenated blood from the pulmonary veins.
Which chamber pumps oxygenated blood out the aorta to the systemic circuit? -left ventricle -left atrium -right ventricle -right atrium
-left ventricle Correct Yes, the left ventricle pumps oxygenated blood out the aorta to the entire body (systemic circuit).
Which chamber receives blood from the superior and inferior vena cavae? -left atrium -right ventricle -right atrium -left ventricle
-right atrium Correct Yes, the right atrium receives unoxygenated blood from the systemic circuit.
There is a note in Mr. G''s chart that he had a color flow Doppler echocardiogram done to prepare for this visit. You pull up the results on the computer. You can see that the blood is flowing up through his mitral valve during systole and that his left ventricle wall is thickened, and his left atrium is dilated. The right ventricle looks normal. His ejection fraction is 43% normal levels are 55-75% (Heart Rhythm Society, 2013). How does Mr. G's altered blood flow explain his signs and symptoms? Let's use one of the diagrams you have already labeled to explain it.
1. When LEFT VENTRICLE contracts, some blood goes up through the mitral valve into the LEFT ATRIUM . Turbulent flow through valve causes SYSTOLIC murmur, LEFT ATRIUM is over-filled and DILATED. 2. Because some blood re-entered the LEFT ATRIUM less is pumped out into AORTA - EJECTION fraction is only is only 43&. 3. Less blood enters the AORTA so SBP is LOW. Baroreceptor reflex causes INCREASED heart rate; wall of overworked left ventricle becomes THICKER 4. Because it is already partly full from the ventricle, LEFT ATRIUM accepts less blood from the LUNGS. The LUNGS over fill with fluid; resulting in DIFFICULTY breathing.
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beatml/beat, end diastolic volume (EDV) is 140 mlml, and end systolic volume (ESV) is 30 mlml.
9.9 L/min Correct Cardiac output is the product of heart rate times stroke volume. Cardiac output increases to meet increased metabolic demand, often by increasing both heart rate and stroke volume at the same time. This occurs, for example, during maximal exercise, when cardiac output may increase to four or five times the resting level.
How does heart rate affect stroke volume?
A high heart rate reduces the end diastolic volume (EDV) and stroke volume (SV), because there is less time for ventricular filling. Correct A slow heart rate allows more time for ventricular filling. Conversely, a faster heart rate allows less time. The amount the heart fills during diastole (EDV) has a direct impact on stroke volume.
Which of these structures conduct(s) action potentials the slowest?
AV node Correct Action potentials slow down as they pass through the AV node. This gives the atria time to finish contracting before the ventricles are depolarized.
Which of the following can be heard with a stethoscope most easily?
Closing of atrioventricular valves Correct Heart sounds are an extremely helpful diagnostic tool that is not invasive. The first heart sound, often described as a lubb, corresponds to the closing of the atrioventricular valves. The second heart sound is a sharper and crisper dupp that corresponds to the closing of the semilunar valves. Consequently, the two heart sounds mark the beginning and the end of ventricular systole.
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
Contractility Correct Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.
These activities change heart rate by changing the balance of parasympathetic and sympathetic stimulation of the heart. Sort each of the activities according to whether it decreases or increases heart rate. Drag the appropriate items to their respective bins.
Correct The balance between parasympathetic and sympathetic stimulation to the heart controls heart rate. Increased parasympathetic activity decreases heart rate, and sympathetic activity increases heart rate.
What is the effect of high blood pressure on cardiac output?
High blood pressure increases afterload and reduces cardiac output (CO). Correct High blood pressure does produce a resistant force to systolic contractions, thus increasing afterload and end systolic volume (ESV). If ESV increases, stroke volume decreases.
The greater the mass of tissue in an organ, the greater its need for an adequate blood supply. Which chamber of the heart has the highest probability of being the site of a myocardial infarction? -right atrium -left atrium -left ventricle -right ventricle
Left Ventricle Correct The left ventricle actively pumps blood to almost all of the body's tissues via the aorta. It has to generate much greater force during contraction than any other heart chamber.
The right tricuspid valve prevents backflow of blood from the right ventricle into the _______________. -left atrium -left ventricle -pulmonary trunk -right atrium
Right Atrium Flow from the right ventricle to the right atrium is prevented by the right tricuspid valve.
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
SA node Correct Like the rest of the intrinsic conduction system, the SA node contains pacemaker cells that spontaneously depolarize. The cells within the SA node, however, depolarize faster than the other cells within the system. This causes action potentials to initiate in the SA node rather than in any of the other structures.
Refer to Focus Figure 18.2, specifically the pressure in the left atrium. Which statement best explains the second rise in atrial pressure on the line graph?
The bicuspid/mitral valve closes; blood is contained within the closed chamber, exerting pressure against the atrial wall. Correct As blood flows into the left atrium, it moves passively into the left ventricle. As the atrium contracts to squeeze remaining blood downward into the ventricle, the pressure in this chamber is reflected from this contraction by the initial rise on the left atrial-pressure graph. As blood fills the ventricle, the ventricle will eventually contract, resulting in a rise in ventricular pressure and forcing the bicuspid valve flaps to close superiorly. As the valve is now closed, the pressure rises slightly in the atrium because blood is forced against the walls of the closed chamber.
Which statement correct regarding the ventricles? -The right ventricle empties into the pulmonary trunk -the left ventricles empties into the pulmonary circuit -the right ventricle forms a complete circle in cross section -the left ventricle has a thinner wall than the right ventricle
The right ventricle empties into the pulmonary trunk Flow from the right ventricle to the right atrium is prevented by the right tricuspid valve.
What best describes afterload?
back pressure exerted by arterial blood Correct Afterload refers to the back pressure exerted by arterial blood, or the pressure that must be overcome for the ventricles to eject blood.
The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?
closing of the atrioventricular valves Correct The QRS complex is a recording of ventricular depolarization. This depolarization begins just prior to the ventricular contraction it initiates. As the ventricles contract, the increase in ventricular pressure closes the atrioventricular valves, beginning isovolumetric contraction. As ventricular pressure increases above the corresponding blood vessel, only then do the semilunar valves open, initiating ventricular ejection.
The first heart sound (the "lub" of the "lub-dup") is caused by __________
closure of the atrioventricular valves Correct The first heart sound (the "lub" of the "lub-dup") is generated by the closure of the atrioventricular valves.
Which of the following would cause a DECREASE in cardiac output (CO)?
decreasing thyroid function (thyroxine) Correct Thyroxine increases basal metabolic rate, respiratory rate, and both heart rate and contractility.
Hypercalcemia could cause ________.
prolonged T wave. Correct The T wave on an ECG tracing represents ventricular repolarization. Repolarization requires the net efflux of K+ ions. Recall that changes in normal concentrations of ions (like Ca2+) in the plasma can affect the ability of other ions to move in and out of the cell.
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells?
the flow of positive ions from adjacent cells Correct Yes, the flow of positive ions from the autorhythmic cells (or adjacent cells) brings the membrane to threshold initiating depolarization of the contractile cell.
What structure in the intrinsic cardiac conduction system determines heart rate? -the cardiac nerve -the sinoatrial (SA) node -the vagus nerve -the atrioventricular (AV) node
the sinoatrial (SA) node Correct The SA node is composed of pacemaker cells that initiate and set the initial pace, or the sinus rhythm, of the heartbeat.
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)?
ventricular systole Correct Left ventricular systole typically produces maximum pressures of around 120 mm Hg. Provide FeedbackNext
Why does a graph of the membrane potential of living pacemaker cells never demonstrate a flat line? -Hyper-polarization of pacemaker cells triggers the opening of slow Na+ channels and starts a new slow depolarization phase. -The vagus nerve continually stimulates the pacemaker cells. -As pacemaker cells hyperpolarize, the excessive influx of K+K+ ions increases the membrane potential. -Repolarization of pacemaker cells triggers the opening of fast Ca2+Ca2+ channels, triggering another rapid depolarization.
Hyperpolarization of pacemaker cells triggers the opening of slow Na+ channels and starts a new slow depolarization phase. Correct At the end of an action potential, as repolarization and hyperpolarization occur, slow Na+ channels open, causing the membrane potential to immediately start to increase again (called the pacemaker potential), eventually triggering another action potential.
Suppose a patient develops a myocardial infarction that disables the sinoatrial node. Would the heart still pump blood to the aorta and the pulmonary trunk? -No, because there will be no contraction of the atria. -Yes, because the ventricles will depolarize on their own without nodal stimulation at a rate of 50 times per minute. -No, because there would be no more connection between the atrioventricular node and the bundle branches. -Yes, because the atrioventricular node will still stimulate ventricular systole.
Yes, because the atrioventricular node will still stimulate ventricular systole. Correct The atrioventricular node spontaneously depolarizes similarly to the sinoatrial node, but more slowly. It can lead to the ventricles pumping blood to the aorta and pulmonary trunk around 50 times per minute.
Determine which ECG shows a normal sinus rhythm. -A -B -C -D
-A Correct All waves are clearly present in this ECG of a normal sinus rhythm.
Determine which of the following electrocardiogram (ECG) tracings is missing P waves but is otherwise regular. -A -B -C -D
-B Correct B illustrates a QRS complex and a T wave, but it is missing the P wave.
Which of these muscles is particularly associated with anchoring the right and left atrioventricular valves? -papillary muscles -pectinate muscles -myocardium -trabecular carneae
-Papillary Muscles Papillary muscles contract to tense the right and left atrioventricular valves via the chordae tendineae just before ventricular systole.
Which of these vessels returns blood to the left atrium of the heart? -Pulmonary Veins -Superior Vena Cava -Pulmonary Trunk -Coronary Sinus
-Pulmonary Veins The pulmonary veins transport oxygen-enriched blood from the lungs to the left atrium
Which portion of the electrocardiogram represents the time during which the ventricles are in systole? -P wave -T wave -Q-T interval -QRS complex
-Q-T interval Correct The Q-T interval is the period from the beginning of ventricular depolarization through ventricular repolarization, during which the ventricles are in systole.
Which heart chamber pumps unoxygenated blood out the pulmonary trunk? -left ventricle -left atrium -right ventricle -right atrium
-right ventricle Correct Yes, the right ventricle pumps unoxygenated blood out the pulmonary trunk to the lungs.
The heart is actually (one, two, or three) pumps? -one pump -two pumps -three pumps
-two pumps Correct Yes, the right side of the heart pumps to/from the lungs (pulmonary circuit) and the left side of the heart pumps to/from the rest of the body (the systemic circuit).
Why does this patient have signs and symptoms so different from Mr.G's?
1. Mr. V's partly blocked tricuspid valve restricts blood flow from the RIGHT ATRIUM to the RIGHT VENTRICLE, turbulent blood flow is heard during DIASTOLE as blood is forced through the narrow opening. 2. The RIGHT ATRIUM does not empty normally, so it cannot accept a normal amount of blood from the BODY; blood accumulates in the veins and tissues, causing distended JUGULARS and SWOLLEN tissues. The excess fluid in tissues leads to weight GAIN and a HEAVY feeling in Mr. V's legs.
Calculate the stroke volume if the end diastolic volume (EDV) is 135 mL/beat and the end systolic volume (ESV) is 60 mL/beat.
75 mL/beat Correct The SV is calculated by subtracting the ESV from the EDV. You are comparing the volume of the ventricle at its fullest to its emptiest.
Which best describe the isovolumetric contraction phase of the cardiac cycle?
As ventricular systole starts, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection. Correct This closed pressure system is important for the ventricles to be able to generate enough pressure to open the semilunar valves and eject blood from the heart.
In contrast to a skeletal muscle cell action potential, why does the action potential for a cardiac muscle cell contain a "plateau" phase?
Cardiac muscle cells contain slow Ca2+Ca2+ channels in their sarcolemma that continue to allow influx of Ca2+Ca2+ ions after Na+Na+ channels are inactivated. Correct Fast voltage-gated Na+Na+ channels are open only for a very brief time before they are inactivated, but the resulting depolarization opens slow Ca2+Ca2+ channels that start a positive feedback cycle that temporarily keeps the membrane potential high.
So why is Mr. G's mitral regurgitation causing a systolic murmur? Remember, a murmur is caused by abnormal turbulent blood flow. -Because his mitral valve leaks, when the ventricles contract, they push blood back up through it into the right atrium -Because his mitral valve leaks, when the ventricles contract, they push blood back up through it into the aorta -Because his mitral valve leaks, when the ventricles contract, they push blood back up through it into the left atrium -Because his mitral valve leaks, when the ventricles relax, they push blood back up through it into the left
Because his mitral valve leaks, when the ventricles contract, they push blood back up through it into the left atrium Correct Good work. Knowing the cardiac cycle helps explain why Mr. G's leaky mitral valve causes a systolic murmur. Let's look at the other problems it might be causing him
What causes the abnormal swishing or whooshing sound that is heard as blood regurgitates back into an atrium from its associated ventricle? -blood turbulence -aortic recoil -semilunar valve closure -pulmonary trunk expansion
Blood Turbulence
Drag and drop the labels onto the figure to identify the events associated with the cardiac cycle. Use each label once.
Correct The cardiac cycle reflects pressure changes in several key structures of the heart; the volume changes as blood moves through the heart and, finally, the electrical events associated with heart contraction. Review Focus Figure 18.2 for each of the line graphs and their relation to the cardiac cycle.
Which of the following is an effect of epinephrine, norepinephrine, and thyroxine?
Increase contractility Correct Epinephrine, norepinephrine, and thyroxine secreted by the sympathetic nervous system directly increase contractility and heart rate, for the overall effect of increasing cardiac output. Likewise, end systolic volume would decrease with increased contractility.
Baby A was scheduled for surgery to repair her atrial septal defect. The operation went well, and she is recovering nicely. Her mother wants to know whether she will need transfusions since her blood pressure was so low before the surgery. Will she need transfusions to maintain her systemic volume? -No. When she had the shunt, her body increased its blood volume to keep blood pressure up. For the rest of her life, her blood pressure will be too high. -Yes. Her body has become adapted to having low blood pressure and will not raise it up again. For the rest of her life, she will have low blood pressure. -No. Now that the shunt has been repaired, her blood is not being diverted from the systemic circuit into the pulmonary circuit, and her blood pressure should return to normal. -Yes. The shunt was causing excess blood to enter her lungs, and now that it is repaired, that excess blood has been removed.
No. Now that the shunt has been repaired, her blood is not being diverted from the systemic circuit into the pulmonary circuit, and her blood pressure should return to normal. Correct Good work! In this pediatric case, the nurse's job involves assessment, interpretation of lab results, and educating a concerned mother. Like many of us, patients often remember things much better when you present them in pictures. You have made Mrs. A feel much better, as she understands what is going on with her baby and how the treatment should help. She will be better able to identify any problems as she cares for her daughter at home.
Refer to Focus Figure 18.2, specifically the graph reflecting pressure changes in the cardiac cycle. Why is the dicrotic notch important?
Reflects an increase in aortic pressure as blood rebounds against the closed aortic semilunar valve Correct Review each of the pressure line graphs in Focus Figure 18.2. As ventricular pressure decreases below aortic pressure, the aortic semilunar valve closes. In response, blood rebounds against this closed valve, producing a slight increase in the aortic pressure. This is shown on the line graph as the dicrotic notch.
The echocardiogram revealed an atrial septal defect as well as confirming the enlarged right ventricle and pulmonary trunk. Baby A's systemic blood pressure is also decreased. What is the most likely explanation? Since she has a pulmonary infection, more blood is being diverted to her lungs; this distends her pulmonary trunk and leaves less blood in the systemic circuit. -Her repeated pulmonary infections have weakened the right side of her heart, so it is enlarged. -Since blood is moving between her atria, the blood in her ventricles and arteries is staying where it is, distending those structures. -Since blood is moving from her systemic circuit into her pulmonary circuit, the pulmonary circuit is distended and the systemic circuit is low on blood.
Since blood is moving from her systemic circuit into her pulmonary circuit, the pulmonary circuit is distended and the systemic circuit is low on blood.
Mr. G has mitral regurgitation. How has this caused a systolic murmur? First of all, let's sort out what is happening during systole and diastole.
Systole -Ventricles are contracting -Blood is leaving the heart -Semilunar Valves are open -AV valves are closed -Blood is flowing through semilunar valves Diastole -Ventricles are relaxed -AV Valves are open -Blood is entering the heart -Semilunar valves are closed -Blood is flowing through AV valves
What would happen to the SA node if a chemical blocker was used to reduce transport of Na+ into the pacemaker cells? -The SA node would depolarize more quickly, decreasing the heart rate. -The SA node would depolarize more quickly, increasing the heart rate. -The SA node would depolarize more slowly, reducing the heart rate. -The SA node would depolarize more slowly, increasing the heart rate. -There will be no change.
The SA node would depolarize more slowly, reducing the heart rate. Correct Diffusion of Na+ into the pacemaker cell causes a gradual depolarization of the cell membrane, called the pacemaker potential. If the rate of depolarization slows down, it will take longer for the membrane to reach threshold and trigger the next action potential, which will reduce heart rate.
What is the role of the atrioventricular bundle?
The atrioventricular bundle provides the only pathway for electrical signals to pass from the atria to the ventricles. Correct The atrial cardiac cells are not connected by gap junctions to the ventricular cardiac cells. The only means by which the electrical signals of the heart can pass from atria to ventricles is the atrioventricular bundle.
Mr. G talks in short bursts with frequent breaths. He tells you he used to feel breathless when he was walking, but now he has been having more and more trouble breathing even when he is lying down at night. When you listened to his lungs you heard fluid in them. Could this be due to his heart failure, or is it another problem? -The left side of the heart receives blood from the lungs and pumps it out to the body, so if it fails, blood will remain in the lungs. -If the left side of the heart fails, it will not pump enough blood to the body, and that means less blood will reach the right side of the heart and be sent to the lungs. -The left side of the heart does not have anything to do with the lungs, but if it fails, the right side is going to fail too, and then circulation through the lungs will decrease. -The left side of the heart pumps blood to the lungs, so if it fails, circulation in the lungs will decrease.
The left side of the heart receives blood from the lungs and pumps it out to the body, so if it fails, blood will remain in the lungs. Correct Difficulty breathing, or dyspnea, is a common side effect of left-sided heart failure. It happens when the left side of the heart is not able to move blood out of the lungs to the body fast enough. The right side of the heart, meanwhile, is pumping more blood into the lungs. As a result, the lung capillaries are overfilled, the pulmonary blood pressure is increasing, and more fluid is forced out of the capillaries into the lungs. Mr. G does not feel so bad during the day because when he stands or sits, gravity pulls a lot of his blood into his legs. When he lies down at night, though, much of that blood moves into his chest, and the amount of fluid going into his lungs increases. He may wake up with the feeling that he is drowning −− which is accurate, in a way!
Mr. G's online file also has the results of his recent blood tests. The only thing that looks abnormal is something called ANP - atrial natriuretic peptide. It is elevated. Why would this hormone be elevated in Mr. G, and what is it doing to him? -his hormone comes from damaged ventricles and indicates that Mr. G's left ventricle is beginning to fail. -This hormone comes from the atria and causes the atria and causes the body to release ore K+ in the urine protecting Mr. G against a possibly fatal arrhythmia. -This hormone is the normal secretion from heart muscle cells, and it is elevated because Mr. G's left ventricle is larger. =This hormone comes from the overstretched atrium and makes Mr. G lose more Na+ and water in his uring, lowering blood volume reducing the load on the atrium. -This hormone controls sodium and water retention and is secreted by the adrenal cortex as part of the central response that raises blood pressure.
This hormone comes from the overstretched atrium and makes Mr. G lose more Na+ and water in his urine, lowering blood volume reducing the load on the atrium. Correct Even though they both had rheumatic fever, you can see that Mr. G and Mr. V have completely different heart problems −− one has a leaky valve, and the other a partly blocked valve; one has a systolic murmur, and the other a diastolic murmur. This sort of thing will really confuse you unless you work it out carefully step by step!
What is happening during the "pause" phase when the heart is resting (relaxing)? -Ventricles are filling -Valves are closing -Ventricles are contraction -Atria are contractin
Ventricles are filling
Mr. V has also had a recent echocardiogram and blood work. With tricuspid stenosis, what changes do you expect to see in the echocardiogram report? -dilated right atrium because blood is not flowing down into the right ventricle fast enough -enlarged left ventricle because blood is not flowing out into the body fast enough -decreased ejection fraction because blood cannot flow out into the aorta fast enough -dilated left atrium because blood is not flowing down into the left ventricle fast enough
dilated right atrium because blood is not flowing down into the right ventricle fast enough Correct Sure enough, when you check Mr. V's echocardiogram, you see a dilated right atrium and a slightly dilated superior vena cava. Does this help you to explain Mr. V's other signs and symptoms?
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
fast calcium Correct Yes, unlike nerve cells or cardiac muscle cells, fast calcium channels are responsible for the depolarization phase of the autorhythmic cell action potential. When the fast calcium channels open, calcium rushes into the cell making it less negative (or more positive).
In Baby A, the atrial septal defect did not close at birth. Blood is flowing through her defect in what direction? -from the right atrium into the left atrium -There will be no net flow across the defect. -from the left atrium into the right atrium -from the left atrium into the right ventricle
from the left atrium into the right across Correct Good. Baby A's atrial septal defect did not close properly on her first breath, so now blood is flowing from her left atrium into her right atrium. But that is not what brought her in to the doctor, is it? She is here because of respiratory infections and trouble breathing.
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
gap junctions Correct Yes, action potentials generated by the autorhythmic cells spread waves of depolarization to contractile cells through gap junctions. If the depolarization causes the contractile cells to reach threshold, they will in turn generate an action potential.
What is the period during the cardiac cycle when the valves leading to and from the ventricles are completely closed and blood volume in the ventricles remains constant as the walls contract?
isovolumetric contraction phase Correct The prefix -iso means "equal," so during any isovolumetric stage the volume does not change.
Failure in a particular structure of the heart tends to cause a backup of blood in the lungs, known as pulmonary congestive heart failure. Failure of which structure of the heart would lead to such a backup? -pulmonary semilunar valve -right atrium -left ventricle -right ventricle
left ventricle Correct Failure in the left ventricle can cause increased blood hydrostatic pressure in the lungs, causing fluid buildup in the alveoli.
Repolarization of an autorhythmic cell is due to the opening of which channels?
voltage-gated potassium channels Correct Yes, opening of voltage-gated potassium channels causes positive potassium ions to move out of the cell. This efflux of potassium causes the cell to become more negative inside thus, repolarizing the cell.
During which of these stages are the aortic and pulmonary valves open?
phase 2b Correct During phase 2b, the pressure in the ventricles exceeds that of the aorta and pulmonary trunk, so their valves open and allow blood to be ejected.
One of the changes that occurs in the pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is a decreased efflux of what ion?
potassium Correct Yes, if there is a decreased efflux of potassium while there is a normal influx of sodium, the inside of the cell would become less negative. Thus, threshold would be reached. The ability of these autorhythmic cells to spontaneously depolarize is what results in the pacemaker potential.
As your skeletal muscles contract during physical activity, more blood is returned to the heart.. Which variable would be affected and what would be the outcome of this action
preload would be increased, which would result in a larger cardiac output Correct More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore a larger cardiac output.
Cardiac tamponade results in ineffective pumping of blood by the heart. This is because the excessive amount of fluid in the pericardial cavity will ______. -prevent the visceral layer of the serous pericardium from properly surrounding the heart -prevent the heart from filling properly with blood -prevent proper oxygenation of the blood -interfere with the ability of this fluid to lubricate the serous membranes
prevent the heart from filling properly with blood Correct The heart is wrapped by a double-walled sac called the pericardium. The pericardial cavity lies between the parietal and visceral layers of the serous pericardium. It is filled with a very small amount of serous fluid. If additional fluid fills the pericardial space, it adds pressure on the outside of the heart, preventing it from filling normally.
The presence of an incompetent tricuspid valve would have the direct effect of causing ______. -reduced efficiency in the delivery of blood to the lungs -reduced efficiency in the delivery of blood to the myocardium -reduced efficiency in the delivery of blood from the lungs to the heart -reduced efficiency in the delivery of blood from the head to the heart
reduced efficiency in the delivery of blood to the lungs Correct The tricuspid valve separates the right atrium and the right ventricle. It must remain tightly closed during ventricular contraction so blood can be pumped out of the ventricle and into the pulmonary arteries.
Consider the following characteristics of the cells found in muscle tissue. Which feature is shared by both cardiac muscle and skeletal muscle? -striations -triads -intercalated discs -branched cells
striations Correct Since both cardiac and skeletal muscles possess arrangements of motor proteins in regularly arrayed sarcomeres, they both display the banding known as striations.
