Chapter 18 Test 4

11.Draw a normal ECG pattern. Label and explain the significance of its deflection waves.

See Figure 18.16. The P wave results from depolarization of the atria. The QRS complex results from ventricular depolarization and precedes ventricular contraction. The T wave is caused by ventricular repolarization and precedes ventricular relaxation.

What does tachycardia look like on an ECG

Shorter time between T and P

Q1. Where in the heart are the pacemaker cells located?

Sinoatrial node of right atrium.

What does a right bundle branch block look like?

QRS is longer.

Q7. Is the aortic (left semilunar) valve open during this time (Q6)?

Yes

12.The P wave of an electrocardiogram represents __________. A. atrial depolarization B. ventricular repolarization C. ventricular depolarization D. atrial repolarization

A

Q1. When the pressure in Chamber A is greater than the pressure in Chamber B (PA > PB), is valve 1 open or closed?

Open

Q4. If Chamber A represents the left atrium and Chamber B represents the left ventricle, name the part of the heart represented by the following elements of the diagram above. • a. Valve 1 = • b. Valve 2 = • c. Chamber C =

a. Bicuspid/mitral. b. aortic. c. aorta.

aortic semilunar valve

prevents backflow of blood into the left ventricle

. SV is defined mathematically above. What is its definition in words?

Volume of blood per unit time, e.g., liters per minute or milliliters per second

Q2. What does "diastole" mean?

Relaxation (not contracting).

Q2. How do their action potentials (below) compare to action potentials in a typical neuron?

Action potentials last a LONG time! (Neuron action potentials are over within 1-2 milliseconds.) More subtle thing: gradual upslope of baseline (in the absence of any input), reflecting some Na+ influx at rest. (And upward rise of action potential is, in this case, due to voltage-gated CALCIUM channels, not sodium.)

Q1. The times during which the atria and ventricles contract are already labeled. Where on the diagram are these labels?

At the top of the diagram.

14.The tricuspid valve is located between the __________. A. right and left atria B. right atrium and right ventricle C. right and left ventricles D. left atrium and left ventricle E. right ventricle and the aorta

B

2) Pressure in the ventricles will be highest near the end of the ______. A. P wave B. QRS complex C. T wave

B

2. An ECG provides information about (a) cardiac output, (b) movement of the excitation wave across the heart, (c) coronary circulation, (d) valve impairment.

B

2. The fact that the left ventricular wall is thicker than the right reveals that it (a) pumps a greater volume of blood, (b) pumps blood against greater resistance, (c) expands the thoracic cage, (d) pumps blood through a smaller valve.

B

20.The noncontractile cardiac muscle cells that initiate their own depolarization and cause depolarization of the rest of the heart are called __________. A. Desmosomes B. pacemaker cells C. gap junctions D. intercalated discs E. cardioinhibitory centers

B

29.An enlarged R wave on an ECG would indicate __________. A. a myocardial infarction B. an enlarged ventricle C. cardiac ischemia D. repolarization abnormalities

B

pulmonary semilunar valve

prevents backflow of blood into the right ventricle

Q4. How does the autonomic nervous system affect heart rate through its effects on "funny channels"?

The sympathetic nervous system increases heart rate by opening more of the "funny channels" in the pacemaker cell membranes, allowing faster entry of sodium and quicker attainment of threshold. The parasympathetic nervous system does the opposite: it closes some of the "funny channels" in the pacemaker cells, thus extending the time taken to reach threshold.

6. Name the valve that has just two cusps.

The mitral (left atrioventricular) valve has two cusps.

17. PREDICT If the mitral valve were insufficient, would you expect to hear the murmur (of blood flowing through the valve that should be closed) during ventricular systole or diastole?

The murmur of mitral insufficiency occurs during ventricular systole (because this is when the valve should be closed, and the murmur is due to blood leaking through the incompletely closed valve into the atrium).

16.The second heart sound is associated with the closing of which valve(s)?

The second heart sound is associated with the closing of the semilunar valves.

mitral (bicuspid) valve

valve between the left atrium and left ventricle

tricuspid valve

valve between the right atrium and right ventricle

15. Which of the following would lead to a decrease in heart rate? A. Norepinephrine B. Exercise C. sharply decreased blood volume D. parasympathetic stimulation

D

Q6. When the left ventricle pumps blood into the aorta, is left ventricular pressure greater than, less than, or equal to aortic pressure?

LV pressure is greater.

Q1. Is an ECG graph more like an EMG graph or an action potential graph? Why?

An ECG is more like an EMG, in that it is typically generated using surface electrodes (on the skin) that simultaneously capture signals from many muscle cells simultaneously. An action potential represents the membrane potential for a single cell, based on very tiny electrodes placed just inside and just outside the cell membrane.

3) Which valves close shortly after the ventricles stop contracting? A. Atrioventricular (AV) B. Semilunar (SL) C. Both AV and SL

B

7. Freshly oxygenated blood is first received by the (a) right atrium, (b) left atrium, (c) right ventricle, (d) left ventricle.

B

7.The most muscular chamber of the heart is the __________. A. right atrium B. left ventricle C. right ventricle D. left atrium

B

. During systemic circulation, blood leaves the __________. A. right atrium and flows directly to the lungs B. lungs and flows directly to the left atrium C. left ventricle and flows directly to the aorta D. right ventricle and flows directly to the lungs E. right ventricle and flows directly to the aorta

C

10. The inferior vena cava brings blood from the lower regions of the body and empties into the __________. A. Aorta B. left ventricle C. right atrium D. left atrium E. right ventricle

C

10.The role of the atrioventricular node (AV node) is to __________. A. conduct impulses to the sinoatrial node (SA node) B. initiate a sinus rhythm C. slow down impulses so that the atria can contract to fill the adjacent ventricles with blood D. initiate ventricular depolarization

C

2. The portion of the intrinsic conduction system located in the superior interventricular septum is the (a) AV node, (b) SA node, (c) AV bundle, (d) subendocardial conducting network.

C

Q11. Predict if the aortic valve is open or closed during this time (Q9). Explain.

closed. LV pressure gets pretty low (see Wiggers diagram), while aortic pressure remains pretty high.

Q7. Finally, let's connect blood pressures to the heart valves, remembering the earlier slides about valves. • a. Under what conditions should the aortic semilunar (SL) valve be open? • when the ________________ pressure is higher than the _______________ pressure • b. Under what conditions should the left atrioventricular (AV) valve be open? • when the ________________ pressure is higher than the _______________ pressure • c. Look on the Wiggers diagram for indications of when these valves open and close. Do they match your predictions in (a) and (b)?

a. left ventricular, aortic. b. left atrial, left ventricular. c. (They should.)

Q6. Find the atrial and ventricular pressures in the Wiggers diagram. Do the pressure increases and decreases occur about where you would expect, based on Q5?

(They should, mostly.)

13. Describe the electrical event in the heart that occurs during each of the following: (a) the QRS complex of the ECG; (b) the T wave of the ECG; (c) the P-R interval of the ECG.

(a) The QRS wave occurs during ventricular depolarization. (b) The T wave of the ECG occurs during ventricular repolarization. (c) The P-R interval of the ECG occurs during atrial depolarization and the conduction of the action potential through the rest of the intrinsic conduction system.

8. Which of the following statements are true? (a) The left ventricle wall is thicker than the right ventricle wall. (b) The left ventricle pumps blood at a higher pressure than the right ventricle. (c) The left ventricle pumps more blood with each beat than the right ventricle. Explain.

(a) True. The left ventricle wall is thicker than the right. (b) True. The left ventricle pumps blood at much higher pressure than the right ventricle because the left ventricle supplies the whole body, whereas the right ventricle supplies only the lungs. (c) False. Each ventricle pumps the same amount of blood with each beat. If this were not true, blood would back up in either the systemic or pulmonary circulation (because the two ventricles are in series).

13.The second heart sound (the "dup" of "lub-dup") is caused by the __________. A. closure of the semilunar valves B. opening of the atrioventricular valves C. closure of the atrioventricular valves D. opening of the semilunar valves

A

5.Into which chamber of the heart do the pulmonary veins deliver blood? A. left atrium B. right atrium C. right ventricle D. left ventricle

A

How does depolarization spread through the heart?

Duh answer: gap junctions in intercalated discs. Better answer: SA node => AV node => AV bundle (bundle of His) => bundle branches => Purkinje fibers.

What is the function of the heart?

Duh answer: pump blood. Slightly better: deliver nutrients and hormones, remove wastes. Those needs will CHANGE over time, so the heart's pumping must change as well (speed up, slow down).

13.The normal pacemaker of the heart is the __________. A. AV node B. AV bundle C. bundle branches D. subendocardial conducting network (Purkinje fibers) E. SA node

E

15.When the mitral valve closes, it prevents the backflow of blood from the __________. A. right ventricle into the pulmonary trunk B. right atrium into the right ventricle C. left atrium into the left ventricle D. left ventricle into the aorta E. left ventricle into the left atrium

E

19.APPLY After running to catch a bus, Josh noticed that his heart was beating faster than normal and was pounding forcefully in his chest. How did his increased HR and SV come about?

Exercise activates the sympathetic nervous system. Sympathetic nervous system activity increases heart rate. It also directly increases ventricular contractility, thereby increasing Josh's stroke volume.

Q1. Label the 4 colored arcs: • Atrial diastole • Atrial systole • Ventricular diastole • Ventricular systole

First note that systole = contraction, diastole = relaxation. Inner circle: tan is atrial systole, turquoise is atrial diastole. Outer circle: purple is ventricular systole, peach is ventricular diastole.

Q2. Explain why the AV values are open most of the time, while the SL valves are closed most of the time.

For most of the cardiac cycle, pressure is higher on the "upstream" (atrial) side of the AV valves, keeping them open, and higher on the "downstream" (arterial) side of the SL valves, keeping them closed.

Q8. Predict whether the bicuspid (mitral, or left AV) valve is open during this time (Q6). Explain.

It's closed. Contraction of LV means high pressure in LV, exceeding pressure in LA, so valve is closed.

Q8. The heart sounds, "lubb" (S1) and "dubb" or "dupp" (S2), are shown at the bottom of the Wiggers diagram. Guess what causes these sounds, then check your book or the Internet to see if you are right. Now take a final fond look back at the Wiggers diagram. Note that we were able to navigate our way through this very complicated figure by connecting electrical activity (ECG) to contractile activity and volumes, connecting volumes to pressures, and connecting pressures to valve activities. Hooray -- you have conquered the Wiggers diagram!

Lubb/S1 = closing of AV valves. Dupp/S2 = closing of SL valves.

Q5. Compare and contrast the roles of Na+, K+, and Ca2+ in neuronal and cardiac action potentials.

Na+ entry serves to depolarize both neurons and cardiac pacemaker cells, but in cardiac pacemaker cells some Na+ channels are open at rest, causing the cells to spontaneously depolarize to threshold. In neurons, voltage-gated Na+ channels are responsible for action potentials along axons, but in cardiac pacemaker cells action potentials are due to voltage-gated Ca2+ channels. K+ exit through voltage-gated channels repolarizes both neurons and cardiac pacemaker cells.

Q9. When the ventricles are filling with blood, is the blood pressure in the left ventricle pressure greater than the blood pressure in the left atrium?

No

Q10. Is the bicuspid (mitral) valve open or closed during this time (Q9)?

Open

Q2. When the pressure in Chamber C is less than the pressure in Chamber B (PC < PA), is valve 2 open or closed?

Open

Q3. What relationship between pressures in Chambers A, B, and C results in valves 1 and 2 both being closed?

PC > PB > PA.

Q1. One of the pictures below represents end-diastolic volume (EDV; that is, the volume at the end of ventricular diastole), and the other represents endsystolic volume (ESV). Which is which? Based on these numbers, what is the stroke volume (SV)?

Panel A = EDV, panel B = ESV. SV = 100 mL.

What does wolf parkinson white syndrome look like? (depolarization through AV node without pausing)

QRS immediately after P wave. PR is shorter than normal.

Q3. List the structures in the heart, specialized for conduction, through which electrical depolarization spreads, in the order in which they depolarize..

Sinoatrial (SA) node => atrial conduction fibers (internodal fibers) => atrioventricular (AV) node => AV bundle / bundle of His => left and right bundle branches => Purkinje fibers (subendocardial conducting network).

Q5. Using your answer to Q4, what do you predict would happen to the net cardiac output (CO) if Valve 2 did not close completely?

Some blood from aorta would get back into LV, lowering net cardiac output. (You could think of this as sort of equivalent to lowering CO by raising ESV.)

4. In the frontal section of the heart below, name the structures indicated by a-g. Which heart chamber receives oxygen-poor blood from veins? Which chamber pumps blood into the systemic circulation? Which blood vessel transports blood toward the lungs? Diagram shows frontal section of heart, anterior view. Identify the following seven structures labeled (a) through (g). Structure (a), the largest artery in the body, arches above the heart in this view. Structure (b) is a large blood vessel that routes the blood from the heart to the lungs. Structure (c) is a thin-walled chamber of the heart. It makes up most of the heart's base. Structure (d) is a thin-walled chamber of the heart. Blood enters this chamber through three veins. Structure (e) is a thick-walled chamber of the heart that pumps blood into the aorta. Structure (f) is a thick-walled chamber of the heart that pumps blood into the pulmonary circuit. Structure (g) is a large vein that returns blood to the heart from body areas below the diaphragm.

The structures are (a) aorta (b) pulmonary trunk (c) left atrium (d) right atrium (e) left ventricle, (f) right ventricle, (g) inferior vena cava. The right atrium (d) receives oxygen-poor blood. The left ventricle (e) pumps blood into the systemic circulation. The pulmonary trunk (b) transports blood toward the lungs.

Q2. On the previous slide, the depolarization of the ventricles (QRS complex) and the repolarization of ventricles (T wave) both result in positive-voltage deflections. How is that possible?

We do not need a complete explanation, but the simple answer is that the last cells to depolarize are the first to repolarize, and a wave of positive charges spreading in one direction looks electrically similar to a wave of negative charges spreading in the opposite direction.

Q1. Can the whole heart still be depolarized if one of the yellow branches is blocked?

Yes - charges can still spread via regular gap junctions between ordinary cardiac muscle cells.

Q2. At which points do the valves close in this pic? • AV valves • SL valves

AV valves close near start of ventricular systole (see arrows representing the possibility of backward flow, pushing valves closed). SL valves are closed at the top of the cycle but, after opening just after the start of ventricular systole, close again just after the end of ventricular systole (see arrows representing the possibility of backward flow, pushing valves closed).

Q3. How long does repolarization of the ventricles take, according to the previous slide? Is that similar in duration to the depolarization of the ventricles, or longer? What does this tell us about the mechanism of depolarization? (That is, do the pacemaker cells tell the other cells when to REpolarize, too?)

About 0.15 seconds, according to the previous slide. This is slower than the time taken by the ventricles to depolarize (more like 0.1 seconds, according to the previous slide), and suggests that repolarization does NOT spread through the same high-speed pathways (SA node, AV node, AV bundle, etc.) used for depolarization.

15. The activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus, (a) vagus nerve stimulation of the heart reduces heart rate, (b) sympathetic nerve stimulation of the heart decreases time available for ventricular filling, (c) sympathetic stimulation of the heart increases its force of contraction, (d) all of the above.

D

24.What part of the heart is considered the systemic circuit pump? A. the right ventricle B. the right atrium C. the pericardium D. the left ventricle

D

3.The superior chambers of the heart are called the __________. A. Ventricles B. Cavae C. coronary chambers D. atria

D

2. Choose the correct sequence of electrical current flow through the heart wall. A. subendocardial conducting network, AV node, AV bundle, right and left bundle branches, SA node B. AV node, subendocardial conducting network, AV node, AV bundle, right and left bundle branches C. SA node, AV node, AV bundle, right and left bundle branches, subendocardial conducting network D. SA node, subendocardial conducting network, AV node, AV bundle, right and left bundle branches E. AV node, SA node, subendocardial conducting network, AV bundle, right and left bundle branches

C

2. The sequence of contraction of the heart chambers is (a) random, (b) left chambers followed by right chambers, (c) both atria followed by both ventricles, (d) right atrium, right ventricle, left atrium, left ventricle.

C

4. Freshly oxygenated blood is delivered to the __________, and then it passes into the __________ to be pumped to the body tissues (systemic circuit). A. left ventricle; left atrium B. right atrium; right ventricle C. left atrium; left ventricle D. right ventricle; right atrium

C

7. In the heart, which of the following apply? (1) Action potentials are conducted from cell to cell across the myocardium via gap junctions, (2) the SA node sets the pace for the heart as a whole, (3) spontaneous depolarization of cardiac cells can occur in the absence of nerve stimulation, (4) cardiac muscle can continue to contract for long periods in the absence of oxygen. (a) all of the above, (b) 1, 3, 4, (c) 1, 2, 3, (d) 2, 3.

C

During pulmonary circulation, blood leaves the __________. A. right atrium and flows directly to the left ventricle B. ventricle and flows directly to the lungs C. right ventricle and flows directly to the lungs D. right atrium and flows directly to the lungs E. right ventricle and flows directly to the aorta

C

5.From the perspective of blood returning from the systemic circuit, identify the correct sequence of blood flow through the chambers of the heart. A. right ventricle, left ventricle, left atrium, lungs, right atrium B. left atrium, left ventricle, right ventricle, right atrium, lungs C. lungs, right ventricle, left ventricle, right atrium, left atrium D. right atrium, right ventricle, lungs, left atrium, left ventricle E. left ventricle, left atrium, lungs, right ventricle, right atrium

D

Cardiac output is __________. A. the number of impulses fired by the SA node in one minute B. the amount of blood filling each ventricle at the end of diastole C. the number of times the heart beats in one minute D. the amount of blood pumped out of each ventricle in one minute E. the amount of blood pumped out of the heart during every ventricular contraction

D

13. What is cardiac output, and how is it calculated?

Cardiac output is the amount of blood pumped out of each ventricle in 1 minute. It can be calculated using the following equation: cardiac output = heart rate x stroke volume.

Q7. If given one "line" of a Wiggers diagram, be able to fill in the next "line," according to the following order: • A. ECG • B. timing of atrial and ventricular systole and diastole • C. atrial and ventricular volumes • D. atrial, ventricular, and aortic pressures • E. status of heart valves (open or closed) • Example:Graph atrial AND ventricular volumes for the periods shown. Don't worry about the exact shapes of the curves, just show whether volume is increasing or decreasing in each chamber during each period.

Example. Each chamber's volume should decrease during its systole and increase during its diastole. Again, the exact shape isn't important.

Q6. Calculate cardiac output from a graph; or, if given any two of the variables in the cardiac output equation, calculate the third one. • Example: calculate cardiac output from this.

Example. Max volume = EDV = 130 mL. Minimum volume = ESV = 70 mL. SV = EDV minus ESV = 130 mL minus 70 mL = 60 mL/beat. HR = 1 beat/sec = 60 beats/min. (Read this off the graph; notice that the cycle repeats about once per second.) CO = HR*SV = (60 beats/min)*(60 mL/beat) = 3600 mL/min. (You wouldn't need to get this exact number, as long as your basic methods were right.)

Q8. If given a description of an alteration in cardiac conduction, describe and draw how that would affect the ECG. • Example: Premature atrial depolarizations originating outside the SA node.

Example. Occasional premature atrial depolarizations would mean that sometimes a P wave follows the T wave more closely than expected. For a person at rest or in a steady state, the intervals (e.g., T-to-P) should be fairly constant from beat to beat, but this disorder would result in more variability in the length of the T-to-P intervals.

Q4. Now let's connect the mechanical events (contraction and relaxation) to chamber volumes. • a. When the ventricle contracts, what happens to its volume of blood? • b. When does most of the change in volume occur, according to the diagram? • c. What do you think happens to the atrial volume during atrial contraction?

a. Blood volume decreases. b. At the start of the contraction. c. Atrial volume should decrease when atrial volume contracts.

Q3. Compare the timing of a chamber's electrical depolarization and its mechanical contraction. a. Which must begin first, depolarization or contraction? b. Once the muscle cells are fully depolarized, does contraction stop?

a. Depolarization. b. No - contraction continues until the cells repolarize.

Q5. Now let's connect the changes in chamber volumes to changes in the blood pressure within those chambers. • a. When a contracting chamber reduces its volume, what (if anything) will happen to the pressure on the blood in that chamber?• b. When a relaxing chamber increases its volume, what (if anything) will happen to the pressure on the blood in that chamber?

a. Pressure increases. b. Pressure decreases.