Chapter 20

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

calcium channels remaining open.

Name the inner lining of the heart.

endocardium

When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?

fast calcium

Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?

gap junctions

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle

The pulmonary veins carry blood to the

heart

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

heart rate will decrease and cells will hyperpolarize.

What fibrous structure functions to anchor the atrioventricular valves in a closed position?

Chordae tendineae

________ is when the heart can't maintain adequate cardiac output.

Heart failure

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

Name the ridged bundles of muscle found projecting inside the right atrium.

Pectinate muscles

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 is the function of the coronary circulation?

Provide a blood supply to the heart

Abnormally slow depolarization of the ventricles would most change the shape of the ________ in an ECG tracing.

QRS complex

Depolarization of the ventricles is represented on an electrocardiogram by the

QRS complex

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

SA node

If there is a complete block between the SA node and the AV node, how would the ECG be affected?

The rate of P waves will be faster than the rate of QRS complexes

The inferior point of the heart is called the

apex

The ________ carry blood away from the heart.

arteries

On an ECG, what phase of the cardiac cycle is masked by the QRS complex?

atrial repolarization

Identify the ear like flaps that are attached to the top chambers of the heart.

auricle

The ________ valve prevents backward flow into the left atrium.

bicuspid

Identify the valve found between the left atrium and left ventricle.

bicuspid valve

With each ventricular systole,

blood pressure increases

During the T wave of the electrocardiogram, the ventricles are

both repolarizing and relaxing.

A slower-than-normal heart rate is called

bradycardia

During the plateau phase of the cardiac action potential, which ion is entering the cardiac muscle cell?

calcium

Heart rate is controlled by neurons of the cardiovascular center located in the

medulla oblongata

Excess fluid in the ________ causes cardiac tamponade.

pericardial cavity

The heart lies within the ________ cavity.

pericardial cavity

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

The papillary muscles function to __________.

prevent the AV valves from reversing into the atria

Contractions of the papillary muscles

prevent the atrioventricular valves from reversing into the atria.

The ________ circuit carries blood to and from the lungs.

pulmonary

Blood leaves the right ventricle by passing through the

pulmonary valve

The right ventricle pumps blood to the

right and left lungs

Blood returning to the heart from the systemic circuit first enters the

right atrium

Which chamber receives blood from the superior and inferior vena cavae?

right atrium

Coronary veins empty into the

right atrium.

Which chamber of the heart exits into the pulmonary trunk?

right ventricle

Which heart chamber pumps unoxygenated blood out the pulmonary trunk?

right ventricle

Analysis of the electrocardiogram can reveal all of the following except

stroke volume.

The contraction phase of the cardiac cycle is called

systole

A faster-than-normal heart rate is called

tachycardia

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

tetany

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.

Identify the right atrioventricular valve.

tricuspid valve

The heart is actually (one, two, or three) pumps?

two pumps

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 T wave on an ECG tracing represents

ventricular repolarization.

The epicardium is also known as the __________.

visceral pericardium

Repolarization of an autorhythmic cell is due to the opening of which channels?

voltage-gated potassium channels

What is the ligamentum arteriosum?

A remnant of the ductus arteriosus

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

AV node

The first heart sound is heard when the

AV valves close

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

AV valves only

Name the needle like ridges of muscle lining the ventricles.

Trabeculae carneae

In cardiac muscle,

about 20 percent of the calcium ion required for contraction comes from outside the cell.

End-systolic volume is defined as the

amount of blood remaining in a ventricle after contraction.

The left ventricle pumps blood to the

aorta

Most of the middle layer in the heart wall is composed of

cardiac muscle cells

If you know both the heart rate and stroke volume, you can calculate the __________.

cardiac output

The cusps (leaflets) of atrioventricular valves attach directly to

chordae tendineae.

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

closing of the atrioventricular valves.

Which event occurs during ventricular systole?

closing of the bicuspid and tricuspid valves

The P wave of the electrocardiogram is closely followed by __________.

contraction of both atria

The first blood vessels to branch from the aorta are the ________ arteries.

coronary

The ________ deliver(s) blood to the myocardium.

coronary arteries

The P wave of the electrocardiogram is a signal from

depolarization of the atria.

The relaxation phase of the cardiac cycle is called

diastole

What does the ECG wave tracing represent?

electrical activity in the heart

The ________ is the volume of blood in a ventricle at the beginning of systole.

end-diastolic volume

The amount of blood remaining in the ventricle when the semilunar valve closes is the

end-systolic volume.

The foramen ovale in the fetal heart is located in the

interatrial septum

Intercalated discs serve to transfer ________ from cell to cell.

ionic currents, electrical signals, action potentials, the force of contraction

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

isovolumetric contraction, ventricular ejection, isovolumetric relaxation

Blood returning to the heart from the pulmonary circuit first enters the

left atrium

Which heart chamber receives blood from the pulmonary veins?

left atrium

Most of the mass of the heart lies

left of the midline

Identify the most muscular chamber.

left ventricle

What heart chamber pushes blood through the aortic semilunar valve?

left ventricle

Which chamber pumps oxygenated blood out the aorta to the systemic circuit?

left ventricle

The pulmonary arteries carry blood to the

lungs

The coronary sulcus is a groove that

marks the border between the atria and ventricles.