Chapter 18: The Heart and Cardiovascular System Part 3

At a heart rate of 69 beats/minute, a cardiac cycle lasts

1 second

The ________ valve opens when left ventricular pressure exceeds aortic blood pressure.

aortic

Figure 18-2 What occurs at "A" on the graph?

aortic semilunar valve opens

In the non-exercising heart, which event of the cardiac cycle lasts the longest?

atrial diastole

What is the first phase of the cardiac cycle?

atrial systole

Which phase of the cardiac cycle is the shortest?

atrial systole

List the phases of the cardiac cycle. (Module 18.10A)

atrial systole, atrial diastole, ventricular systole, ventricular diastole

The contraction phase of the upper chambers of the heart is called

atrial systole.

Describe the pressures in the atria and ventricles that would cause the opening of the AV valves

Pressure in the atria would be greater than the pressure in the ventricles

What structure carries the electrical signal from the septum of the heart through the ventricular myocardium?

Purkinje fibers

Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?

SA node

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

SA node

________ is to contraction as ________ is to relaxation.

Systole; diastole

Why does tetany not occur in cardiac muscle? (Module 18.11A)

Tetany does not occur because cardiac muscle has a long refractory period that continues until relaxation is well under way so summation cannot occur, and thus tetany cannot occur.

During the isovolumetric contraction phase of ventricular systole, the

atrioventricular valves and semilunar valves are closed.

Give the alternate terms for heart contraction and heart relaxation. (Module 18.9B)

The alternate term for heart contraction is systole and the alternate term for heart relaxation is diastole.

If the cells of the SA node failed to function, how would the heart rate be affected? (Module 18.12B)

The heart would beat slower because the AV node would be the pacemaker.

Figure 18-2 What occurs at the area labeled "D" on the graph?

both AV valves open and diastolic refilling begins

If the pacemaker cells in the SA node become more permeable to potassium ions,

both heart rate will decrease and membrane will hyperpolarize

What electrolyte (ion) is responsible for the plateau in the cardiac action potential?

calcium

The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?

closing of the atrioventricular valves

The first heart sound ("lubb") is associated with

closing of the mitral valve.

What statement is true regarding pressures and volumes in the cardiac ventricles?

The pressure is greater in the left ventricle, but the volumes are equal in the two chambers.

What causes the aortic semilunar valve to close

greater pressure in the aorta than in the left ventricle

In cardiac muscle, the fast depolarization phase of the action potential is the result of ________ membrane permeability to ________ ions.

increased; sodium

Figure 18-2 What occurs at the circled label "4" on the graph?

isovolumetric contraction

What are the two phases of ventricular systole? (Module 18.10B)

isovolumetric contraction and ventricular ejection

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.

isovolumetric contraction, ventricular ejection, isovolumetric relaxation

Figure 18-2 What does the circle label "5" indicate on the graph?

peak systolic pressure

List the three stages of an action potential in a cardiac muscle cell. (Module 18.11B)

rapid depolarization, plateau, and repolarization

Figure 18-2 What occurs at "B" on the graph?

semilunar valve closes

As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit

tetany

What structure prevents the electrical signals generated in the SA node from passing directly from the atrium through to the ventricles below?

the cardiac skeleton

Which of the following is greater during left ventricular systole?

the peak pressure in the ventricle

Tetanic muscle contractions don't occur in a normal cardiac muscle because

the refractory period lasts until the muscle relaxes.

The normal pacemaker of the heart is located in

the sinoatrial node.

If the connection between the SA node and AV node becomes blocked,

the ventricles will beat more slowly.

What does the QRS complex represent in the ECG wave tracing?

ventricular depolarization

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

ventricular diastole

The relaxation phase of the lower chambers of the heart is called

ventricular diastole.

The phase in the cardiac cycle when the mitral valve is closed and the aortic valve is open is the

ventricular ejection of ventricular systole.

During which phase of the cardiac cycle is the blood pumped to the body?

ventricular systole

What event causes the closing of the AV valves, which results in the first heart sound?

ventricular systole

Isovolumetric contraction is associated with which cardiac cycle phase?

ventricular systole - first phase

The long plateau phase of the cardiac muscle action potential is due to

voltage-gated calcium channels remaining open.

The mitral valve closing is associated with all of the following except

when the left atrial pressure exceeds the left ventricular pressure.

Compare the duration of atrial and ventricular systole at a representative heart rate of 75 bpm. (Module 18.9C)

Atrial systole has a duration of 100 msec, and ventricular systole has a duration of 270 msec.

Which event does NOT happen during ventricular diastole?

Atrioventricular valves close because of the contracting ventricles.

Define autorhythmicity. (Module 18.12A)

Autorhythmicity is the ability of the heart to contract without neural or hormonal stimulation.

The following are structural components of the conducting system of the heart.1. Purkinje fibers 2. AV bundle 3. AV node 4. SA node 5. bundle branches The sequence in which excitation would move through this system is which of the following?

4, 3, 2, 5, 1

The heart pumps approximately ________ milliliters of blood each minute.

6,000

Pacemaker cells isolated from the SA node generate action potentials at ________ beats per minute.

80-100

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

AV node

Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?

AV node

During ventricular systole, the

AV valves are closed.

The first heart sound is heard when the

AV valves close.

Increased pressure in the ventricles would close what valve(s)

AV valves only

Which of the following statements most accurately defines what is happening during the second phase of ventricular systole of the cardiac cycle?

Blood is being ejected from the ventricles through open semilunar valves.

Which parts of the following statement are true? The AV node delivers the stimulus to the AV bundle, located within the interventricular septum.

Both parts of the statement are true.

Define cardiac cycle. (Module 18.9A)

Cardiac cycle is the period between the start of one heartbeat and the beginning of the next.

Which of the following can be heard with a stethoscope most easily?

Closing of atrioventricular valves

Which of the following is correct about the filling of the ventricles?

Most blood flows passively into the ventricles through open AV valves.

Contraction of the atria results from which wave of depolarization on the ECG tracing?

P wave

As the heart rate slows, ________ get(s) longer.

diastole

What does the ECG wave tracing represent?

electrical activity in the heart

In cardiac muscle, calcium ions

enter the cell through slow voltage gated ion channels.

Pacemaker cells in the SA node

generate action potentials that spread to the myocardium.