Chapter 18 Mastering A&P

The Frank-Starling Law of the heart describes why stroke volume is directly influenced by all of the following factors except

the conduction of impulses from the SA node to the AV node

The function of heart valves is to

enforce one-way blood flow through the heart

Heart activities that can be monitored via the ECG include

flow of depolarization across the heart

What part of the intrinsic conduction system stimulates the atrioventricular (AV) node?

sinoatrial (SA) node

The ________ is located in the posterior wall of the right atrium and is often referred to as the pacemaker of the heart.

sinoatrial node

The fibrous skeleton of the heart serves all the following functions except

speeds the conduction of the depolarization between the atria and the ventricles

The presence of an incompetent mitral valve, which allows backflow of blood, would have the direct effect of causing ______.

reduced efficiency in the delivery of blood to the systemic circuit

The bicuspid valve is closed

when the ventricles are in systole

Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beat, end diastolic volume (EDV) is 140 ml, and end systolic volume (ESV) is 30 ml.

9.9 L/min

Arrange these elements of the intrinsic conduction system in the order that a depolarizing impulse travels during a normal heartbeat. Rank from first to last. Do not overlap any tiles.

1) SA Node 2) Intermodal Pathways 3) AV Node 4) AV Bundle 5) Bundle Branches 6) Purkinje Fibers

Match the cardiac components in the left column to the blanks near their functions on the right.

1. AV node: Delay(s) occurs here while atria contract 2. SA node: Set(s) the pace for the entire heart 3. AV bundle : Electrical link(s) between atria and ventricles 4. Purkinje fibers: Convey(s) the impulse throughout the ventricular walls 5. Bundle branches: Convey(s) the impulse down the interventricular septum 6. Internodal pathways: Link(s) between the SA node and AV node

Match the term in the left column to the blanks near their definition on the right.

1. Cardiac output (CO): the volume of blood per minute pumped out by one ventricle 2. End diastolic volume (EDV): the volume of blood in one ventricle before contraction 3. Stroke volume (SV): the volume of blood per heart beat pumped out by one ventricle 4. Venous return (VR): the volume of blood per minute flowing into one atrium 5. End systolic volume (ESV): the volume of blood in one ventricle after contraction 6. Heart rate (HR): the number of heart beats per minute

What is the expected heart rate when a heart is removed from a living body?

100 beats/min

Given an end diastolic volume (EDV) of 120 ml / beat and an end systolic volume (ESV) of 50 ml / beat, the stroke volume (SV) would be ________.

70 ml/beat

Select the correct statement about cardiac output.

A slow heart rate increases end diastolic volume, stroke volume, and force of contraction.

Which of these structures conduct(s) action potentials the slowest?

AV Node

Gap junctions found at the intercalated discs in the myocardium function to

Allow rapid flow of depolarizations between the myocardial cells

Determine which of the following electrocardiogram (ECG) tracings is missing P waves but is otherwise regular.

B

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 left atrium.

Which of the following receive(s) blood during ventricular systole?

Both aorta and pulmonary trunk

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.

Decreases Heart Rate: Lying down, Digesting a meal Increases Heart Rate: Standing up, Fright or Anger, Exercise

Which of the following increases stroke volume?

Exercise

The phase of the cardiac cycle when the ventricles are not contracting is referred to as systole.

False

The role of the chordae tendineae is to open the AV valves at the appropriate time.

False

A man enters the emergency department complaining of brief episodes of chest pain over several days. His history includes smoking, a diet heavy in saturated fats, and lack of exercise. Given just this information, what is he most likely suffering from and what is he at high risk for?

He suffers from angina pectoris caused by coronary arteries that are occluded by fatty deposits, and is at high risk for a myocardial infarction.

Predict the changes in heart rate, stroke volume, and cardiac output for each of the following conditions by filling out the table below. Drag the appropriate labels to their respective targets.

Increased sympathetic activity: Increase HR, SV, CO Increase Preload: No change in HR, increase SV and CO Increased exercise: Increase HR, SV, CO Increase contractility: No change in HR, increase SV and CO

Which portion of the electrocardiogram represents the depolarization wave received by the atria from the sinoatrial (SA) node?

P Wave

As your muscles contract during 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 increase cardiac output.

The right ventricle pumps blood into the

Pulmonary circuit

The right atrioventricular valve prevents backflow of blood from the right ventricle into the __________.

Right atrium

Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?

SA Node

The order of impulse conduction in the heart, from beginning to end, is __________.

SA node, AV node, bundle of His, bundle branches, and Purkinje fibers

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: AV valves are closed, Semilunar valves are open, Ventricles are contracting, Blood is leaving the heart, Blood is flowing through semilunar valves Diastole: Ventricles are relaxed, Blood is entering the heart, AV valves are open, Semilunar valves are closed, Blood is flowing through AV valves

Which of the following is true during ventricular systole?

The AV valves are closed

Which of the following is equivalent to the ventricular volume during isovolumetric contraction?

The end diastolic volume (EDV)

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 pumps blood into the body, so when it fails, less blood will be pumped into the arteries.

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 and the increased pressure will cause edema.

Select the correct statement about the structure of the heart wall.

The myocardium is the layer of the heart that actually contracts.

During the ventricular ejection phase of the cardiac cycle, which of the following is true?

The semilunar valves are open

Why would tricuspid stenosis cause a diastolic murmur?

The tricuspid valve is partly blocked, so when blood is flowing through it, there will be a noise of turbulent blood flow. Blood flows through the tricuspid during diastole, so that is when you hear the murmur.

When the atria contract, which of the following is true?

The ventricles are in diastole

Congestive heart failure means that the pumping efficiency of the heart has decreased to the point that there is inadequate delivery of blood to body tissues.

True

Each ventricle pumps the same volume of blood with each beat.

True

Heart rate can have a significant influence on stroke volume.

True

The myocardium receives its blood supply from the coronary arteries.

True

Mr. V has right-side heart failure, which is accompanied by specific symptoms. Other patients may have other causes of their right-side heart failure, such as COPD - do you think the systemic (body-wide) symptoms will remain the same? What is the most easily recognized symptom?

Yes, because when the right heart can't pump blood into the pulmonary circuit as quickly as it receives it, backup in the systemic circuit will always cause peripheral edema.

Tachycardia is

a heart rate consistently above 100 beats/minute

The term for chest pain associated with transient ischemia of the heart that does not result in cell death is

angina pectoris

What best describes afterload?

back pressure exerted by arterial blood

Common causes of congestive heart failure include all of the following except

cardiac tamponade

An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.

contractility

The QRS wave of an ECG is produced by

depolarization of the ventricles

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 able to flow down into the right ventricle fast enough

Which of the following is equivalent to the ventricular volume during isovolumetric relaxation?

end systolic volume (ESV)

Norepinephrine and epinephrine act on the heart by ________.

increasing both heart rate and contractility

Which of the following is not true about venous return:

it increases heart rate

The __________ ventricle has a thicker wall because

left - it pumps into the high pressure systemic circuit

Blood in the pulmonary veins is traveling to the

left atrium

Failure in a particular chamber of the heart tends to cause a backup of blood in the lungs, known as pulmonary congestive heart failure. Failure of which chamber of the heart would lead to such a backup?

left ventricle

When a myocardial infarct damages the right ventricle, reducing its pumping efficiency, which of the following will occur:

peripheral edema

The left ventricular wall of the heart is thicker than the right ventricular wall in order to ________.

pump blood with greater force

The pacemaker potential refers to

the slow influx of sodium ions that brings autorhythmic cells to threshold for initiating an action potential

What is the main function of heart valves?

to prevent backward flow of blood

A myocardial infarct that caused death and scarring of a region of the left ventricle would most likely cause stroke volume of that ventricle to be decreased.

true

Each ventricle pumps the same volume of blood with each beat.

true

Heart rate can have a significant influence on stroke volume.

true

Vagal tone refers to the fact that parasympathetic input controls the resting heart rate.

true

Most of the decrease in ventricular volume takes place during which phase of the cardiac cycle?

ventricular ejection

Most of the increase in left ventricular volume takes place during what phase of the cardiac cycle?

ventricular filling